server.go

// Copyright 2012-2020 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package server

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"math/rand"
	"net"
	"net/http"
	"regexp"

	// Allow dynamic profiling.
	_ "net/http/pprof"
	"os"
	"path"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/nats-io/jwt/v2"
	"github.com/nats-io/nkeys"
	"github.com/nats-io/nuid"

	"github.com/nats-io/nats-server/v2/logger"
)

const (
	// Interval for the first PING for non client connections.
	firstPingInterval = time.Second

	// This is for the first ping for client connections.
	firstClientPingInterval = 2 * time.Second
)

// Info is the information sent to clients, routes, gateways, and leaf nodes,
// to help them understand information about this server.
type Info struct {
	ID                string   `json:"server_id"`
	Name              string   `json:"server_name"`
	Version           string   `json:"version"`
	Proto             int      `json:"proto"`
	GitCommit         string   `json:"git_commit,omitempty"`
	GoVersion         string   `json:"go"`
	Host              string   `json:"host"`
	Port              int      `json:"port"`
	Headers           bool     `json:"headers"`
	AuthRequired      bool     `json:"auth_required,omitempty"`
	TLSRequired       bool     `json:"tls_required,omitempty"`
	TLSVerify         bool     `json:"tls_verify,omitempty"`
	TLSAvailable      bool     `json:"tls_available,omitempty"`
	MaxPayload        int32    `json:"max_payload"`
	JetStream         bool     `json:"jetstream,omitempty"`
	IP                string   `json:"ip,omitempty"`
	CID               uint64   `json:"client_id,omitempty"`
	ClientIP          string   `json:"client_ip,omitempty"`
	Nonce             string   `json:"nonce,omitempty"`
	Cluster           string   `json:"cluster,omitempty"`
	Dynamic           bool     `json:"cluster_dynamic,omitempty"`
	Domain            string   `json:"domain,omitempty"`
	ClientConnectURLs []string `json:"connect_urls,omitempty"`    // Contains URLs a client can connect to.
	WSConnectURLs     []string `json:"ws_connect_urls,omitempty"` // Contains URLs a ws client can connect to.
	LameDuckMode      bool     `json:"ldm,omitempty"`

	// Route Specific
	Import        *SubjectPermission `json:"import,omitempty"`
	Export        *SubjectPermission `json:"export,omitempty"`
	LNOC          bool               `json:"lnoc,omitempty"`
	InfoOnConnect bool               `json:"info_on_connect,omitempty"` // When true the server will respond to CONNECT with an INFO
	ConnectInfo   bool               `json:"connect_info,omitempty"`    // When true this is the server INFO response to CONNECT

	// Gateways Specific
	Gateway           string   `json:"gateway,omitempty"`             // Name of the origin Gateway (sent by gateway's INFO)
	GatewayURLs       []string `json:"gateway_urls,omitempty"`        // Gateway URLs in the originating cluster (sent by gateway's INFO)
	GatewayURL        string   `json:"gateway_url,omitempty"`         // Gateway URL on that server (sent by route's INFO)
	GatewayCmd        byte     `json:"gateway_cmd,omitempty"`         // Command code for the receiving server to know what to do
	GatewayCmdPayload []byte   `json:"gateway_cmd_payload,omitempty"` // Command payload when needed
	GatewayNRP        bool     `json:"gateway_nrp,omitempty"`         // Uses new $GNR. prefix for mapped replies

	// LeafNode Specific
	LeafNodeURLs  []string `json:"leafnode_urls,omitempty"`  // LeafNode URLs that the server can reconnect to.
	RemoteAccount string   `json:"remote_account,omitempty"` // Lets the other side know the remote account that they bind to.
}

// Server is our main struct.
type Server struct {
	gcid uint64
	stats
	mu                  sync.Mutex
	kp                  nkeys.KeyPair
	prand               *rand.Rand
	info                Info
	configFile          string
	optsMu              sync.RWMutex
	opts                *Options
	running             bool
	shutdown            bool
	reloading           bool
	listener            net.Listener
	listenerErr         error
	gacc                *Account
	sys                 *internal
	js                  *jetStream
	accounts            sync.Map
	tmpAccounts         sync.Map // Temporarily stores accounts that are being built
	activeAccounts      int32
	accResolver         AccountResolver
	clients             map[uint64]*client
	routes              map[uint64]*client
	routesByHash        sync.Map
	remotes             map[string]*client
	leafs               map[uint64]*client
	users               map[string]*User
	nkeys               map[string]*NkeyUser
	totalClients        uint64
	closed              *closedRingBuffer
	done                chan bool
	start               time.Time
	http                net.Listener
	httpHandler         http.Handler
	httpBasePath        string
	profiler            net.Listener
	httpReqStats        map[string]uint64
	routeListener       net.Listener
	routeListenerErr    error
	routeInfo           Info
	routeInfoJSON       []byte
	routeResolver       netResolver
	routesToSelf        map[string]struct{}
	leafNodeListener    net.Listener
	leafNodeListenerErr error
	leafNodeInfo        Info
	leafNodeInfoJSON    []byte
	leafURLsMap         refCountedUrlSet
	leafNodeOpts        struct {
		resolver    netResolver
		dialTimeout time.Duration
	}
	leafRemoteCfgs     []*leafNodeCfg
	leafRemoteAccounts sync.Map

	quitCh           chan struct{}
	shutdownComplete chan struct{}

	// Tracking Go routines
	grMu         sync.Mutex
	grTmpClients map[uint64]*client
	grRunning    bool
	grWG         sync.WaitGroup // to wait on various go routines

	cproto     int64     // number of clients supporting async INFO
	configTime time.Time // last time config was loaded

	logging struct {
		sync.RWMutex
		logger      Logger
		trace       int32
		debug       int32
		traceSysAcc int32
	}

	clientConnectURLs []string

	// Used internally for quick look-ups.
	clientConnectURLsMap refCountedUrlSet

	lastCURLsUpdate int64

	// For Gateways
	gatewayListener    net.Listener // Accept listener
	gatewayListenerErr error
	gateway            *srvGateway

	// Used by tests to check that http.Servers do
	// not set any timeout.
	monitoringServer *http.Server
	profilingServer  *http.Server

	// LameDuck mode
	ldm   bool
	ldmCh chan bool

	// Trusted public operator keys.
	trustedKeys []string
	// map of trusted keys to operator setting StrictSigningKeyUsage
	strictSigningKeyUsage map[string]struct{}

	// We use this to minimize mem copies for requests to monitoring
	// endpoint /varz (when it comes from http).
	varzMu sync.Mutex
	varz   *Varz
	// This is set during a config reload if we detect that we have
	// added/removed routes. The monitoring code then check that
	// to know if it should update the cluster's URLs array.
	varzUpdateRouteURLs bool

	// Keeps a sublist of of subscriptions attached to leafnode connections
	// for the $GNR.*.*.*.> subject so that a server can send back a mapped
	// gateway reply.
	gwLeafSubs *Sublist

	// Used for expiration of mapped GW replies
	gwrm struct {
		w  int32
		ch chan time.Duration
		m  sync.Map
	}

	// For eventIDs
	eventIds *nuid.NUID

	// Websocket structure
	websocket srvWebsocket

	// MQTT structure
	mqtt srvMQTT

	// OCSP monitoring
	ocsps []*OCSPMonitor

	// exporting account name the importer experienced issues with
	incompleteAccExporterMap sync.Map

	// Holds cluster name under different lock for mapping
	cnMu sync.RWMutex
	cn   string

	// For registering raft nodes with the server.
	rnMu      sync.RWMutex
	raftNodes map[string]RaftNode

	// For mapping from a raft node name back to a server name and cluster. Node has to be in the same domain.
	nodeToInfo sync.Map

	// For out of resources to not log errors too fast.
	rerrMu   sync.Mutex
	rerrLast time.Time

	// If there is a system account configured, to still support the $G account,
	// the server will create a fake user and add it to the list of users.
	// Keep track of what that user name is for config reload purposes.
	sysAccOnlyNoAuthUser string
}

// For tracking JS nodes.
type nodeInfo struct {
	name    string
	cluster string
	domain  string
	id      string
	offline bool
	js      bool
}

// Make sure all are 64bits for atomic use
type stats struct {
	inMsgs        int64
	outMsgs       int64
	inBytes       int64
	outBytes      int64
	slowConsumers int64
}

// New will setup a new server struct after parsing the options.
// DEPRECATED: Use NewServer(opts)
func New(opts *Options) *Server {
	s, _ := NewServer(opts)
	return s
}

// NewServer will setup a new server struct after parsing the options.
// Could return an error if options can not be validated.
func NewServer(opts *Options) (*Server, error) {
	setBaselineOptions(opts)

	// Process TLS options, including whether we require client certificates.
	tlsReq := opts.TLSConfig != nil
	verify := (tlsReq && opts.TLSConfig.ClientAuth == tls.RequireAndVerifyClientCert)

	// Created server's nkey identity.
	kp, _ := nkeys.CreateServer()
	pub, _ := kp.PublicKey()

	serverName := pub
	if opts.ServerName != _EMPTY_ {
		serverName = opts.ServerName
	}

	httpBasePath := normalizeBasePath(opts.HTTPBasePath)

	// Validate some options. This is here because we cannot assume that
	// server will always be started with configuration parsing (that could
	// report issues). Its options can be (incorrectly) set by hand when
	// server is embedded. If there is an error, return nil.
	if err := validateOptions(opts); err != nil {
		return nil, err
	}

	info := Info{
		ID:           pub,
		Version:      VERSION,
		Proto:        PROTO,
		GitCommit:    gitCommit,
		GoVersion:    runtime.Version(),
		Name:         serverName,
		Host:         opts.Host,
		Port:         opts.Port,
		AuthRequired: false,
		TLSRequired:  tlsReq && !opts.AllowNonTLS,
		TLSVerify:    verify,
		MaxPayload:   opts.MaxPayload,
		JetStream:    opts.JetStream,
		Headers:      !opts.NoHeaderSupport,
		Cluster:      opts.Cluster.Name,
		Domain:       opts.JetStreamDomain,
	}

	if tlsReq && !info.TLSRequired {
		info.TLSAvailable = true
	}

	now := time.Now().UTC()

	s := &Server{
		kp:           kp,
		configFile:   opts.ConfigFile,
		info:         info,
		prand:        rand.New(rand.NewSource(time.Now().UnixNano())),
		opts:         opts,
		done:         make(chan bool, 1),
		start:        now,
		configTime:   now,
		gwLeafSubs:   NewSublistWithCache(),
		httpBasePath: httpBasePath,
		eventIds:     nuid.New(),
		routesToSelf: make(map[string]struct{}),
		httpReqStats: make(map[string]uint64), // Used to track HTTP requests
	}

	// Trusted root operator keys.
	if !s.processTrustedKeys() {
		return nil, fmt.Errorf("Error processing trusted operator keys")
	}

	// If we have solicited leafnodes but no clustering and no clustername.
	// However we may need a stable clustername so use the server name.
	if len(opts.LeafNode.Remotes) > 0 && opts.Cluster.Port == 0 && opts.Cluster.Name == _EMPTY_ {
		opts.Cluster.Name = opts.ServerName
	}

	if opts.Cluster.Name != _EMPTY_ {
		// Also place into mapping cn with cnMu lock.
		s.cnMu.Lock()
		s.cn = opts.Cluster.Name
		s.cnMu.Unlock()
	}

	s.mu.Lock()
	defer s.mu.Unlock()

	// Place ourselves in some lookup maps.
	ourNode := string(getHash(serverName))
	s.nodeToInfo.Store(ourNode, nodeInfo{serverName, opts.Cluster.Name, opts.JetStreamDomain, info.ID, false, opts.JetStream})

	s.routeResolver = opts.Cluster.resolver
	if s.routeResolver == nil {
		s.routeResolver = net.DefaultResolver
	}

	// Used internally for quick look-ups.
	s.clientConnectURLsMap = make(refCountedUrlSet)
	s.websocket.connectURLsMap = make(refCountedUrlSet)
	s.leafURLsMap = make(refCountedUrlSet)

	// Ensure that non-exported options (used in tests) are properly set.
	s.setLeafNodeNonExportedOptions()

	// Setup OCSP Stapling. This will abort server from starting if there
	// are no valid staples and OCSP policy is to Always or MustStaple.
	if err := s.enableOCSP(); err != nil {
		return nil, err
	}

	// Call this even if there is no gateway defined. It will
	// initialize the structure so we don't have to check for
	// it to be nil or not in various places in the code.
	if err := s.newGateway(opts); err != nil {
		return nil, err
	}

	// If we have a cluster definition but do not have a cluster name, create one.
	if opts.Cluster.Port != 0 && opts.Cluster.Name == _EMPTY_ {
		s.info.Cluster = nuid.Next()
	} else if opts.Cluster.Name != _EMPTY_ {
		// Likewise here if we have a cluster name set.
		s.info.Cluster = opts.Cluster.Name
	}

	// This is normally done in the AcceptLoop, once the
	// listener has been created (possibly with random port),
	// but since some tests may expect the INFO to be properly
	// set after New(), let's do it now.
	s.setInfoHostPort()

	// For tracking clients
	s.clients = make(map[uint64]*client)

	// For tracking closed clients.
	s.closed = newClosedRingBuffer(opts.MaxClosedClients)

	// For tracking connections that are not yet registered
	// in s.routes, but for which readLoop has started.
	s.grTmpClients = make(map[uint64]*client)

	// For tracking routes and their remote ids
	s.routes = make(map[uint64]*client)
	s.remotes = make(map[string]*client)

	// For tracking leaf nodes.
	s.leafs = make(map[uint64]*client)

	// Used to kick out all go routines possibly waiting on server
	// to shutdown.
	s.quitCh = make(chan struct{})
	// Closed when Shutdown() is complete. Allows WaitForShutdown() to block
	// waiting for complete shutdown.
	s.shutdownComplete = make(chan struct{})

	// Check for configured account resolvers.
	if err := s.configureResolver(); err != nil {
		return nil, err
	}
	// If there is an URL account resolver, do basic test to see if anyone is home.
	if ar := opts.AccountResolver; ar != nil {
		if ur, ok := ar.(*URLAccResolver); ok {
			if _, err := ur.Fetch(""); err != nil {
				return nil, err
			}
		}
	}
	// For other resolver:
	// In operator mode, when the account resolver depends on an external system and
	// the system account can't fetched, inject a temporary one.
	if ar := s.accResolver; len(opts.TrustedOperators) == 1 && ar != nil &&
		opts.SystemAccount != _EMPTY_ && opts.SystemAccount != DEFAULT_SYSTEM_ACCOUNT {
		if _, ok := ar.(*MemAccResolver); !ok {
			s.mu.Unlock()
			var a *Account
			// perform direct lookup to avoid warning trace
			if _, err := fetchAccount(ar, s.opts.SystemAccount); err == nil {
				a, _ = s.fetchAccount(s.opts.SystemAccount)
			}
			s.mu.Lock()
			if a == nil {
				sac := NewAccount(s.opts.SystemAccount)
				sac.Issuer = opts.TrustedOperators[0].Issuer
				sac.signingKeys = map[string]jwt.Scope{}
				sac.signingKeys[s.opts.SystemAccount] = nil
				s.registerAccountNoLock(sac)
			}
		}
	}

	// For tracking accounts
	if err := s.configureAccounts(); err != nil {
		return nil, err
	}

	// Used to setup Authorization.
	s.configureAuthorization()

	// Start signal handler
	s.handleSignals()

	return s, nil
}

// clusterName returns our cluster name which could be dynamic.
func (s *Server) ClusterName() string {
	s.mu.Lock()
	cn := s.info.Cluster
	s.mu.Unlock()
	return cn
}

// Grabs cluster name with cluster name specific lock.
func (s *Server) cachedClusterName() string {
	s.cnMu.RLock()
	cn := s.cn
	s.cnMu.RUnlock()
	return cn
}

// setClusterName will update the cluster name for this server.
func (s *Server) setClusterName(name string) {
	s.mu.Lock()
	var resetCh chan struct{}
	if s.sys != nil && s.info.Cluster != name {
		// can't hold the lock as go routine reading it may be waiting for lock as well
		resetCh = s.sys.resetCh
	}
	s.info.Cluster = name
	s.routeInfo.Cluster = name

	// Regenerate the info byte array
	s.generateRouteInfoJSON()
	// Need to close solicited leaf nodes. The close has to be done outside of the server lock.
	var leafs []*client
	for _, c := range s.leafs {
		c.mu.Lock()
		if c.leaf != nil && c.leaf.remote != nil {
			leafs = append(leafs, c)
		}
		c.mu.Unlock()
	}
	s.mu.Unlock()

	// Also place into mapping cn with cnMu lock.
	s.cnMu.Lock()
	s.cn = name
	s.cnMu.Unlock()

	for _, l := range leafs {
		l.closeConnection(ClusterNameConflict)
	}
	if resetCh != nil {
		resetCh <- struct{}{}
	}
	s.Noticef("Cluster name updated to %s", name)
}

// Return whether the cluster name is dynamic.
func (s *Server) isClusterNameDynamic() bool {
	return s.getOpts().Cluster.Name == _EMPTY_
}

// ClientURL returns the URL used to connect clients. Helpful in testing
// when we designate a random client port (-1).
func (s *Server) ClientURL() string {
	// FIXME(dlc) - should we add in user and pass if defined single?
	opts := s.getOpts()
	scheme := "nats://"
	if opts.TLSConfig != nil {
		scheme = "tls://"
	}
	return fmt.Sprintf("%s%s:%d", scheme, opts.Host, opts.Port)
}

func validateCluster(o *Options) error {
	if err := validatePinnedCerts(o.Cluster.TLSPinnedCerts); err != nil {
		return fmt.Errorf("cluster: %v", err)
	}
	// Check that cluster name if defined matches any gateway name.
	if o.Gateway.Name != "" && o.Gateway.Name != o.Cluster.Name {
		if o.Cluster.Name != "" {
			return ErrClusterNameConfigConflict
		}
		// Set this here so we do not consider it dynamic.
		o.Cluster.Name = o.Gateway.Name
	}
	return nil
}

func validatePinnedCerts(pinned PinnedCertSet) error {
	re := regexp.MustCompile("^[a-f0-9]{64}$")
	for certId := range pinned {
		entry := strings.ToLower(certId)
		if !re.MatchString(entry) {
			return fmt.Errorf("error parsing 'pinned_certs' key %s does not look like lower case hex-encoded sha256 of DER encoded SubjectPublicKeyInfo", entry)
		}
	}
	return nil
}

func validateOptions(o *Options) error {
	if o.LameDuckDuration > 0 && o.LameDuckGracePeriod >= o.LameDuckDuration {
		return fmt.Errorf("lame duck grace period (%v) should be strictly lower than lame duck duration (%v)",
			o.LameDuckGracePeriod, o.LameDuckDuration)
	}
	if int64(o.MaxPayload) > o.MaxPending {
		return fmt.Errorf("max_payload (%v) cannot be higher than max_pending (%v)",
			o.MaxPayload, o.MaxPending)
	}
	// Check that the trust configuration is correct.
	if err := validateTrustedOperators(o); err != nil {
		return err
	}
	// Check on leaf nodes which will require a system
	// account when gateways are also configured.
	if err := validateLeafNode(o); err != nil {
		return err
	}
	// Check that authentication is properly configured.
	if err := validateAuth(o); err != nil {
		return err
	}
	// Check that gateway is properly configured. Returns no error
	// if there is no gateway defined.
	if err := validateGatewayOptions(o); err != nil {
		return err
	}
	// Check that cluster name if defined matches any gateway name.
	if err := validateCluster(o); err != nil {
		return err
	}
	if err := validateMQTTOptions(o); err != nil {
		return err
	}
	if err := validateJetStreamOptions(o); err != nil {
		return err
	}
	// Finally check websocket options.
	return validateWebsocketOptions(o)
}

func (s *Server) getOpts() *Options {
	s.optsMu.RLock()
	opts := s.opts
	s.optsMu.RUnlock()
	return opts
}

func (s *Server) setOpts(opts *Options) {
	s.optsMu.Lock()
	s.opts = opts
	s.optsMu.Unlock()
}

func (s *Server) globalAccount() *Account {
	s.mu.Lock()
	gacc := s.gacc
	s.mu.Unlock()
	return gacc
}

// Used to setup Accounts.
// Lock is held upon entry.
func (s *Server) configureAccounts() error {
	// Create the global account.
	if s.gacc == nil {
		s.gacc = NewAccount(globalAccountName)
		s.registerAccountNoLock(s.gacc)
	}

	opts := s.opts

	// Check opts and walk through them. We need to copy them here
	// so that we do not keep a real one sitting in the options.
	for _, acc := range s.opts.Accounts {
		var a *Account
		if acc.Name == globalAccountName {
			a = s.gacc
		} else {
			a = acc.shallowCopy()
		}
		if acc.hasMappings() {
			// For now just move and wipe from opts.Accounts version.
			a.mappings = acc.mappings
			acc.mappings = nil
			// We use this for selecting between multiple weighted destinations.
			a.prand = rand.New(rand.NewSource(time.Now().UnixNano()))
		}
		acc.sl = nil
		acc.clients = nil
		s.registerAccountNoLock(a)

		// If we see an account defined using $SYS we will make sure that is set as system account.
		if acc.Name == DEFAULT_SYSTEM_ACCOUNT && opts.SystemAccount == _EMPTY_ {
			s.opts.SystemAccount = DEFAULT_SYSTEM_ACCOUNT
		}
	}

	// Now that we have this we need to remap any referenced accounts in
	// import or export maps to the new ones.
	swapApproved := func(ea *exportAuth) {
		for sub, a := range ea.approved {
			var acc *Account
			if v, ok := s.accounts.Load(a.Name); ok {
				acc = v.(*Account)
			}
			ea.approved[sub] = acc
		}
	}
	var numAccounts int
	s.accounts.Range(func(k, v interface{}) bool {
		numAccounts++
		acc := v.(*Account)
		// Exports
		for _, se := range acc.exports.streams {
			if se != nil {
				swapApproved(&se.exportAuth)
			}
		}
		for _, se := range acc.exports.services {
			if se != nil {
				// Swap over the bound account for service exports.
				if se.acc != nil {
					if v, ok := s.accounts.Load(se.acc.Name); ok {
						se.acc = v.(*Account)
					}
				}
				swapApproved(&se.exportAuth)
			}
		}
		// Imports
		for _, si := range acc.imports.streams {
			if v, ok := s.accounts.Load(si.acc.Name); ok {
				si.acc = v.(*Account)
			}
		}
		for _, si := range acc.imports.services {
			if v, ok := s.accounts.Load(si.acc.Name); ok {
				si.acc = v.(*Account)
				si.se = si.acc.getServiceExport(si.to)
			}
		}
		// Make sure the subs are running, but only if not reloading.
		if len(acc.imports.services) > 0 && acc.ic == nil && !s.reloading {
			acc.ic = s.createInternalAccountClient()
			acc.ic.acc = acc
			acc.addAllServiceImportSubs()
		}
		acc.updated = time.Now().UTC()
		return true
	})

	// Set the system account if it was configured.
	// Otherwise create a default one.
	if opts.SystemAccount != _EMPTY_ {
		// Lock may be acquired in lookupAccount, so release to call lookupAccount.
		s.mu.Unlock()
		acc, err := s.lookupAccount(opts.SystemAccount)
		s.mu.Lock()
		if err == nil && s.sys != nil && acc != s.sys.account {
			// sys.account.clients (including internal client)/respmap/etc... are transferred separately
			s.sys.account = acc
			s.mu.Unlock()
			// acquires server lock separately
			s.addSystemAccountExports(acc)
			s.mu.Lock()
		}
		if err != nil {
			return fmt.Errorf("error resolving system account: %v", err)
		}

		// If we have defined a system account here check to see if its just us and the $G account.
		// We would do this to add user/pass to the system account. If this is the case add in
		// no-auth-user for $G.
		if numAccounts == 2 && s.opts.NoAuthUser == _EMPTY_ {
			// If we come here from config reload, let's not recreate the fake user name otherwise
			// it will cause currently clients to be disconnected.
			uname := s.sysAccOnlyNoAuthUser
			if uname == _EMPTY_ {
				// Create a unique name so we do not collide.
				var b [8]byte
				rn := rand.Int63()
				for i, l := 0, rn; i < len(b); i++ {
					b[i] = digits[l%base]
					l /= base
				}
				uname = fmt.Sprintf("nats-%s", b[:])
				s.sysAccOnlyNoAuthUser = uname
			}
			s.opts.Users = append(s.opts.Users, &User{Username: uname, Password: uname[6:], Account: s.gacc})
			s.opts.NoAuthUser = uname
		}
	}

	return nil
}

// Setup the account resolver. For memory resolver, make sure the JWTs are
// properly formed but do not enforce expiration etc.
func (s *Server) configureResolver() error {
	opts := s.getOpts()
	s.accResolver = opts.AccountResolver
	if opts.AccountResolver != nil {
		// For URL resolver, set the TLSConfig if specified.
		if opts.AccountResolverTLSConfig != nil {
			if ar, ok := opts.AccountResolver.(*URLAccResolver); ok {
				if t, ok := ar.c.Transport.(*http.Transport); ok {
					t.CloseIdleConnections()
					t.TLSClientConfig = opts.AccountResolverTLSConfig.Clone()
				}
			}
		}
		if len(opts.resolverPreloads) > 0 {
			if s.accResolver.IsReadOnly() {
				return fmt.Errorf("resolver preloads only available for writeable resolver types MEM/DIR/CACHE_DIR")
			}
			for k, v := range opts.resolverPreloads {
				_, err := jwt.DecodeAccountClaims(v)
				if err != nil {
					return fmt.Errorf("preload account error for %q: %v", k, err)
				}
				s.accResolver.Store(k, v)
			}
		}
	}
	return nil
}

// This will check preloads for validation issues.
func (s *Server) checkResolvePreloads() {
	opts := s.getOpts()
	// We can just check the read-only opts versions here, that way we do not need
	// to grab server lock or access s.accResolver.
	for k, v := range opts.resolverPreloads {
		claims, err := jwt.DecodeAccountClaims(v)
		if err != nil {
			s.Errorf("Preloaded account [%s] not valid", k)
			continue
		}
		// Check if it is expired.
		vr := jwt.CreateValidationResults()
		claims.Validate(vr)
		if vr.IsBlocking(true) {
			s.Warnf("Account [%s] has validation issues:", k)
			for _, v := range vr.Issues {
				s.Warnf("  - %s", v.Description)
			}
		}
	}
}

func (s *Server) generateRouteInfoJSON() {
	b, _ := json.Marshal(s.routeInfo)
	pcs := [][]byte{[]byte("INFO"), b, []byte(CR_LF)}
	s.routeInfoJSON = bytes.Join(pcs, []byte(" "))
}

// Determines if we are in pre NATS 2.0 setup with no accounts.
func (s *Server) globalAccountOnly() bool {
	var hasOthers bool

	if s.trustedKeys != nil {
		return false
	}

	s.mu.Lock()
	s.accounts.Range(func(k, v interface{}) bool {
		acc := v.(*Account)
		// Ignore global and system
		if acc == s.gacc || (s.sys != nil && acc == s.sys.account) {
			return true
		}
		hasOthers = true
		return false
	})
	s.mu.Unlock()

	return !hasOthers
}

// Determines if this server is in standalone mode, meaning no routes or gateways.
func (s *Server) standAloneMode() bool {
	opts := s.getOpts()
	return opts.Cluster.Port == 0 && opts.Gateway.Port == 0
}

func (s *Server) configuredRoutes() int {
	return len(s.getOpts().Routes)
}

// activePeers is used in bootstrapping raft groups like the JetStream meta controller.
func (s *Server) ActivePeers() (peers []string) {
	s.nodeToInfo.Range(func(k, v interface{}) bool {
		si := v.(nodeInfo)
		if !si.offline {
			peers = append(peers, k.(string))
		}
		return true
	})
	return peers
}

// isTrustedIssuer will check that the issuer is a trusted public key.
// This is used to make sure an account was signed by a trusted operator.
func (s *Server) isTrustedIssuer(issuer string) bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	// If we are not running in trusted mode and there is no issuer, that is ok.
	if s.trustedKeys == nil && issuer == "" {
		return true
	}
	for _, tk := range s.trustedKeys {
		if tk == issuer {
			return true
		}
	}
	return false
}

// processTrustedKeys will process binary stamped and
// options-based trusted nkeys. Returns success.
func (s *Server) processTrustedKeys() bool {
	s.strictSigningKeyUsage = map[string]struct{}{}
	if trustedKeys != "" && !s.initStampedTrustedKeys() {
		return false
	} else if s.opts.TrustedKeys != nil {
		for _, key := range s.opts.TrustedKeys {
			if !nkeys.IsValidPublicOperatorKey(key) {
				return false
			}
		}
		s.trustedKeys = append([]string(nil), s.opts.TrustedKeys...)
		for _, claim := range s.opts.TrustedOperators {
			if !claim.StrictSigningKeyUsage {
				continue
			}
			for _, key := range claim.SigningKeys {
				s.strictSigningKeyUsage[key] = struct{}{}
			}
		}
	}
	return true
}

// checkTrustedKeyString will check that the string is a valid array
// of public operator nkeys.
func checkTrustedKeyString(keys string) []string {
	tks := strings.Fields(keys)
	if len(tks) == 0 {
		return nil
	}
	// Walk all the keys and make sure they are valid.
	for _, key := range tks {
		if !nkeys.IsValidPublicOperatorKey(key) {
			return nil
		}
	}
	return tks
}

// initStampedTrustedKeys will check the stamped trusted keys
// and will set the server field 'trustedKeys'. Returns whether
// it succeeded or not.
func (s *Server) initStampedTrustedKeys() bool {
	// Check to see if we have an override in options, which will cause us to fail.
	if len(s.opts.TrustedKeys) > 0 {
		return false
	}
	tks := checkTrustedKeyString(trustedKeys)
	if len(tks) == 0 {
		return false
	}
	s.trustedKeys = tks
	return true
}

// PrintAndDie is exported for access in other packages.
func PrintAndDie(msg string) {
	fmt.Fprintln(os.Stderr, msg)
	os.Exit(1)
}

// PrintServerAndExit will print our version and exit.
func PrintServerAndExit() {
	fmt.Printf("nats-server: v%s\n", VERSION)
	os.Exit(0)
}

// ProcessCommandLineArgs takes the command line arguments
// validating and setting flags for handling in case any
// sub command was present.
func ProcessCommandLineArgs(cmd *flag.FlagSet) (showVersion bool, showHelp bool, err error) {
	if len(cmd.Args()) > 0 {
		arg := cmd.Args()[0]
		switch strings.ToLower(arg) {
		case "version":
			return true, false, nil
		case "help":
			return false, true, nil
		default:
			return false, false, fmt.Errorf("unrecognized command: %q", arg)
		}
	}

	return false, false, nil
}

// Public version.
func (s *Server) Running() bool {
	return s.isRunning()
}

// Protected check on running state
func (s *Server) isRunning() bool {
	s.mu.Lock()
	running := s.running
	s.mu.Unlock()
	return running
}

func (s *Server) logPid() error {
	pidStr := strconv.Itoa(os.Getpid())
	return ioutil.WriteFile(s.getOpts().PidFile, []byte(pidStr), 0660)
}

// NewAccountsAllowed returns whether or not new accounts can be created on the fly.
func (s *Server) NewAccountsAllowed() bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.opts.AllowNewAccounts
}

// numReservedAccounts will return the number of reserved accounts configured in the server.
// Currently this is 1, one for the global default account.
func (s *Server) numReservedAccounts() int {
	return 1
}

// NumActiveAccounts reports number of active accounts on this server.
func (s *Server) NumActiveAccounts() int32 {
	return atomic.LoadInt32(&s.activeAccounts)
}

// incActiveAccounts() just adds one under lock.
func (s *Server) incActiveAccounts() {
	atomic.AddInt32(&s.activeAccounts, 1)
}

// decActiveAccounts() just subtracts one under lock.
func (s *Server) decActiveAccounts() {
	atomic.AddInt32(&s.activeAccounts, -1)
}

// This should be used for testing only. Will be slow since we have to
// range over all accounts in the sync.Map to count.
func (s *Server) numAccounts() int {
	count := 0
	s.mu.Lock()
	s.accounts.Range(func(k, v interface{}) bool {
		count++
		return true
	})
	s.mu.Unlock()
	return count
}

// NumLoadedAccounts returns the number of loaded accounts.
func (s *Server) NumLoadedAccounts() int {
	return s.numAccounts()
}

// LookupOrRegisterAccount will return the given account if known or create a new entry.
func (s *Server) LookupOrRegisterAccount(name string) (account *Account, isNew bool) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if v, ok := s.accounts.Load(name); ok {
		return v.(*Account), false
	}
	acc := NewAccount(name)
	s.registerAccountNoLock(acc)
	return acc, true
}

// RegisterAccount will register an account. The account must be new
// or this call will fail.
func (s *Server) RegisterAccount(name string) (*Account, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if _, ok := s.accounts.Load(name); ok {
		return nil, ErrAccountExists
	}
	acc := NewAccount(name)
	s.registerAccountNoLock(acc)
	return acc, nil
}

// SetSystemAccount will set the internal system account.
// If root operators are present it will also check validity.
func (s *Server) SetSystemAccount(accName string) error {
	// Lookup from sync.Map first.
	if v, ok := s.accounts.Load(accName); ok {
		return s.setSystemAccount(v.(*Account))
	}

	// If we are here we do not have local knowledge of this account.
	// Do this one by hand to return more useful error.
	ac, jwt, err := s.fetchAccountClaims(accName)
	if err != nil {
		return err
	}
	acc := s.buildInternalAccount(ac)
	acc.claimJWT = jwt
	// Due to race, we need to make sure that we are not
	// registering twice.
	if racc := s.registerAccount(acc); racc != nil {
		return nil
	}
	return s.setSystemAccount(acc)
}

// SystemAccount returns the system account if set.
func (s *Server) SystemAccount() *Account {
	var sacc *Account
	s.mu.Lock()
	if s.sys != nil {
		sacc = s.sys.account
	}
	s.mu.Unlock()
	return sacc
}

// GlobalAccount returns the global account.
// Default clients will use the global account.
func (s *Server) GlobalAccount() *Account {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.gacc
}

// SetDefaultSystemAccount will create a default system account if one is not present.
func (s *Server) SetDefaultSystemAccount() error {
	if _, isNew := s.LookupOrRegisterAccount(DEFAULT_SYSTEM_ACCOUNT); !isNew {
		return nil
	}
	s.Debugf("Created system account: %q", DEFAULT_SYSTEM_ACCOUNT)
	return s.SetSystemAccount(DEFAULT_SYSTEM_ACCOUNT)
}

// For internal sends.
const internalSendQLen = 256 * 1024

// Assign a system account. Should only be called once.
// This sets up a server to send and receive messages from
// inside the server itself.
func (s *Server) setSystemAccount(acc *Account) error {
	if acc == nil {
		return ErrMissingAccount
	}
	// Don't try to fix this here.
	if acc.IsExpired() {
		return ErrAccountExpired
	}
	// If we are running with trusted keys for an operator
	// make sure we check the account is legit.
	if !s.isTrustedIssuer(acc.Issuer) {
		return ErrAccountValidation
	}

	s.mu.Lock()

	if s.sys != nil {
		s.mu.Unlock()
		return ErrAccountExists
	}

	// This is here in an attempt to quiet the race detector and not have to place
	// locks on fast path for inbound messages and checking service imports.
	acc.mu.Lock()
	if acc.imports.services == nil {
		acc.imports.services = make(map[string]*serviceImport)
	}
	acc.mu.Unlock()

	s.sys = &internal{
		account: acc,
		client:  s.createInternalSystemClient(),
		seq:     1,
		sid:     1,
		servers: make(map[string]*serverUpdate),
		replies: make(map[string]msgHandler),
		sendq:   make(chan *pubMsg, internalSendQLen),
		resetCh: make(chan struct{}),
		sq:      s.newSendQ(),
		statsz:  eventsHBInterval,
		orphMax: 5 * eventsHBInterval,
		chkOrph: 3 * eventsHBInterval,
	}

	s.sys.wg.Add(1)
	s.mu.Unlock()

	// Register with the account.
	s.sys.client.registerWithAccount(acc)

	s.addSystemAccountExports(acc)

	// Start our internal loop to serialize outbound messages.
	// We do our own wg here since we will stop first during shutdown.
	go s.internalSendLoop(&s.sys.wg)

	// Start up our general subscriptions
	s.initEventTracking()

	// Track for dead remote servers.
	s.wrapChk(s.startRemoteServerSweepTimer)()

	// Send out statsz updates periodically.
	s.wrapChk(s.startStatszTimer)()

	// If we have existing accounts make sure we enable account tracking.
	s.mu.Lock()
	s.accounts.Range(func(k, v interface{}) bool {
		acc := v.(*Account)
		s.enableAccountTracking(acc)
		return true
	})
	s.mu.Unlock()

	return nil
}

// Creates an internal system client.
func (s *Server) createInternalSystemClient() *client {
	return s.createInternalClient(SYSTEM)
}

// Creates an internal jetstream client.
func (s *Server) createInternalJetStreamClient() *client {
	return s.createInternalClient(JETSTREAM)
}

// Creates an internal client for Account.
func (s *Server) createInternalAccountClient() *client {
	return s.createInternalClient(ACCOUNT)
}

// Internal clients. kind should be SYSTEM or JETSTREAM
func (s *Server) createInternalClient(kind int) *client {
	if kind != SYSTEM && kind != JETSTREAM && kind != ACCOUNT {
		return nil
	}
	now := time.Now().UTC()
	c := &client{srv: s, kind: kind, opts: internalOpts, msubs: -1, mpay: -1, start: now, last: now}
	c.initClient()
	c.echo = false
	c.headers = true
	c.flags.set(noReconnect)
	return c
}

// Determine if accounts should track subscriptions for
// efficient propagation.
// Lock should be held on entry.
func (s *Server) shouldTrackSubscriptions() bool {
	return (s.opts.Cluster.Port != 0 || s.opts.Gateway.Port != 0)
}

// Invokes registerAccountNoLock under the protection of the server lock.
// That is, server lock is acquired/released in this function.
// See registerAccountNoLock for comment on returned value.
func (s *Server) registerAccount(acc *Account) *Account {
	s.mu.Lock()
	racc := s.registerAccountNoLock(acc)
	s.mu.Unlock()
	return racc
}

// Helper to set the sublist based on preferences.
func (s *Server) setAccountSublist(acc *Account) {
	if acc != nil && acc.sl == nil {
		opts := s.getOpts()
		if opts != nil && opts.NoSublistCache {
			acc.sl = NewSublistNoCache()
		} else {
			acc.sl = NewSublistWithCache()
		}
	}
}

// Registers an account in the server.
// Due to some locking considerations, we may end-up trying
// to register the same account twice. This function will
// then return the already registered account.
// Lock should be held on entry.
func (s *Server) registerAccountNoLock(acc *Account) *Account {
	// We are under the server lock. Lookup from map, if present
	// return existing account.
	if a, _ := s.accounts.Load(acc.Name); a != nil {
		s.tmpAccounts.Delete(acc.Name)
		return a.(*Account)
	}
	// Finish account setup and store.
	s.setAccountSublist(acc)

	acc.mu.Lock()
	if acc.clients == nil {
		acc.clients = make(map[*client]struct{})
	}

	// If we are capable of routing we will track subscription
	// information for efficient interest propagation.
	// During config reload, it is possible that account was
	// already created (global account), so use locking and
	// make sure we create only if needed.
	// TODO(dlc)- Double check that we need this for GWs.
	if acc.rm == nil && s.opts != nil && s.shouldTrackSubscriptions() {
		acc.rm = make(map[string]int32)
		acc.lqws = make(map[string]int32)
	}
	acc.srv = s
	acc.updated = time.Now().UTC()
	acc.mu.Unlock()
	s.accounts.Store(acc.Name, acc)
	s.tmpAccounts.Delete(acc.Name)
	s.enableAccountTracking(acc)
	return nil
}

// lookupAccount is a function to return the account structure
// associated with an account name.
// Lock MUST NOT be held upon entry.
func (s *Server) lookupAccount(name string) (*Account, error) {
	var acc *Account
	if v, ok := s.accounts.Load(name); ok {
		acc = v.(*Account)
	}
	if acc != nil {
		// If we are expired and we have a resolver, then
		// return the latest information from the resolver.
		if acc.IsExpired() {
			s.Debugf("Requested account [%s] has expired", name)
			if s.AccountResolver() != nil {
				if err := s.updateAccount(acc); err != nil {
					// This error could mask expired, so just return expired here.
					return nil, ErrAccountExpired
				}
			} else {
				return nil, ErrAccountExpired
			}
		}
		return acc, nil
	}
	// If we have a resolver see if it can fetch the account.
	if s.AccountResolver() == nil {
		return nil, ErrMissingAccount
	}
	return s.fetchAccount(name)
}

// LookupAccount is a public function to return the account structure
// associated with name.
func (s *Server) LookupAccount(name string) (*Account, error) {
	return s.lookupAccount(name)
}

// This will fetch new claims and if found update the account with new claims.
// Lock MUST NOT be held upon entry.
func (s *Server) updateAccount(acc *Account) error {
	// TODO(dlc) - Make configurable
	if !acc.incomplete && time.Since(acc.updated) < time.Second {
		s.Debugf("Requested account update for [%s] ignored, too soon", acc.Name)
		return ErrAccountResolverUpdateTooSoon
	}
	claimJWT, err := s.fetchRawAccountClaims(acc.Name)
	if err != nil {
		return err
	}
	return s.updateAccountWithClaimJWT(acc, claimJWT)
}

// updateAccountWithClaimJWT will check and apply the claim update.
// Lock MUST NOT be held upon entry.
func (s *Server) updateAccountWithClaimJWT(acc *Account, claimJWT string) error {
	if acc == nil {
		return ErrMissingAccount
	}
	acc.mu.RLock()
	sameClaim := acc.claimJWT != "" && acc.claimJWT == claimJWT && !acc.incomplete
	acc.mu.RUnlock()
	if sameClaim {
		s.Debugf("Requested account update for [%s], same claims detected", acc.Name)
		return nil
	}
	accClaims, _, err := s.verifyAccountClaims(claimJWT)
	if err == nil && accClaims != nil {
		acc.mu.Lock()
		if acc.Issuer == "" {
			acc.Issuer = accClaims.Issuer
		}
		if acc.Name != accClaims.Subject {
			acc.mu.Unlock()
			return ErrAccountValidation
		}
		acc.mu.Unlock()
		s.UpdateAccountClaims(acc, accClaims)
		acc.mu.Lock()
		// needs to be set after update completed.
		// This causes concurrent calls to return with sameClaim=true if the change is effective.
		acc.claimJWT = claimJWT
		acc.mu.Unlock()
		return nil
	}
	return err
}

// fetchRawAccountClaims will grab raw account claims iff we have a resolver.
// Lock is NOT held upon entry.
func (s *Server) fetchRawAccountClaims(name string) (string, error) {
	accResolver := s.AccountResolver()
	if accResolver == nil {
		return _EMPTY_, ErrNoAccountResolver
	}
	// Need to do actual Fetch
	start := time.Now()
	claimJWT, err := fetchAccount(accResolver, name)
	fetchTime := time.Since(start)
	if fetchTime > time.Second {
		s.Warnf("Account [%s] fetch took %v", name, fetchTime)
	} else {
		s.Debugf("Account [%s] fetch took %v", name, fetchTime)
	}
	if err != nil {
		s.Warnf("Account fetch failed: %v", err)
		return "", err
	}
	return claimJWT, nil
}

// fetchAccountClaims will attempt to fetch new claims if a resolver is present.
// Lock is NOT held upon entry.
func (s *Server) fetchAccountClaims(name string) (*jwt.AccountClaims, string, error) {
	claimJWT, err := s.fetchRawAccountClaims(name)
	if err != nil {
		return nil, _EMPTY_, err
	}
	var claim *jwt.AccountClaims
	claim, claimJWT, err = s.verifyAccountClaims(claimJWT)
	if claim != nil && claim.Subject != name {
		return nil, _EMPTY_, ErrAccountValidation
	}
	return claim, claimJWT, err
}

// verifyAccountClaims will decode and validate any account claims.
func (s *Server) verifyAccountClaims(claimJWT string) (*jwt.AccountClaims, string, error) {
	accClaims, err := jwt.DecodeAccountClaims(claimJWT)
	if err != nil {
		return nil, _EMPTY_, err
	}
	if !s.isTrustedIssuer(accClaims.Issuer) {
		return nil, _EMPTY_, ErrAccountValidation
	}
	vr := jwt.CreateValidationResults()
	accClaims.Validate(vr)
	if vr.IsBlocking(true) {
		return nil, _EMPTY_, ErrAccountValidation
	}
	return accClaims, claimJWT, nil
}

// This will fetch an account from a resolver if defined.
// Lock is NOT held upon entry.
func (s *Server) fetchAccount(name string) (*Account, error) {
	accClaims, claimJWT, err := s.fetchAccountClaims(name)
	if accClaims == nil {
		return nil, err
	}
	acc := s.buildInternalAccount(accClaims)
	acc.claimJWT = claimJWT
	// Due to possible race, if registerAccount() returns a non
	// nil account, it means the same account was already
	// registered and we should use this one.
	if racc := s.registerAccount(acc); racc != nil {
		// Update with the new claims in case they are new.
		if err = s.updateAccountWithClaimJWT(racc, claimJWT); err != nil {
			return nil, err
		}
		return racc, nil
	}
	// The sub imports may have been setup but will not have had their
	// subscriptions properly setup. Do that here.
	if len(acc.imports.services) > 0 {
		if acc.ic == nil {
			acc.ic = s.createInternalAccountClient()
			acc.ic.acc = acc
		}
		acc.addAllServiceImportSubs()
	}
	return acc, nil
}

// Start up the server, this will block.
// Start via a Go routine if needed.
func (s *Server) Start() {
	s.Noticef("Starting nats-server")

	gc := gitCommit
	if gc == "" {
		gc = "not set"
	}

	// Snapshot server options.
	opts := s.getOpts()

	s.Noticef("  Version:  %s", VERSION)
	s.Noticef("  Git:      [%s]", gc)
	s.Debugf("  Go build: %s", s.info.GoVersion)
	s.Noticef("  Name:     %s", s.info.Name)
	if opts.JetStream {
		s.Noticef("  Node:     %s", getHash(s.info.Name))
	}
	s.Noticef("  ID:       %s", s.info.ID)

	defer s.Noticef("Server is ready")

	// Check for insecure configurations.
	s.checkAuthforWarnings()

	// Avoid RACE between Start() and Shutdown()
	s.mu.Lock()
	s.running = true
	s.mu.Unlock()

	s.grMu.Lock()
	s.grRunning = true
	s.grMu.Unlock()

	if opts.ConfigFile != _EMPTY_ {
		s.Noticef("Using configuration file: %s", opts.ConfigFile)
	}

	hasOperators := len(opts.TrustedOperators) > 0
	if hasOperators {
		s.Noticef("Trusted Operators")
	}
	for _, opc := range opts.TrustedOperators {
		s.Noticef("  System  : %q", opc.Audience)
		s.Noticef("  Operator: %q", opc.Name)
		s.Noticef("  Issued  : %v", time.Unix(opc.IssuedAt, 0))
		s.Noticef("  Expires : %v", time.Unix(opc.Expires, 0))
	}
	if hasOperators && opts.SystemAccount == _EMPTY_ {
		s.Warnf("Trusted Operators should utilize a System Account")
	}
	if opts.MaxPayload > MAX_PAYLOAD_MAX_SIZE {
		s.Warnf("Maximum payloads over %v are generally discouraged and could lead to poor performance",
			friendlyBytes(int64(MAX_PAYLOAD_MAX_SIZE)))
	}

	// If we have a memory resolver, check the accounts here for validation exceptions.
	// This allows them to be logged right away vs when they are accessed via a client.
	if hasOperators && len(opts.resolverPreloads) > 0 {
		s.checkResolvePreloads()
	}

	// Log the pid to a file
	if opts.PidFile != _EMPTY_ {
		if err := s.logPid(); err != nil {
			s.Fatalf("Could not write pidfile: %v", err)
			return
		}
	}

	// Setup system account which will start the eventing stack.
	if sa := opts.SystemAccount; sa != _EMPTY_ {
		if err := s.SetSystemAccount(sa); err != nil {
			s.Fatalf("Can't set system account: %v", err)
			return
		}
	} else if !opts.NoSystemAccount {
		// We will create a default system account here.
		s.SetDefaultSystemAccount()
	}

	// start up resolver machinery
	if ar := s.AccountResolver(); ar != nil {
		if err := ar.Start(s); err != nil {
			s.Fatalf("Could not start resolver: %v", err)
			return
		}
		// In operator mode, when the account resolver depends on an external system and
		// the system account is the bootstrapping account, start fetching it
		if len(opts.TrustedOperators) == 1 && opts.SystemAccount != _EMPTY_ && opts.SystemAccount != DEFAULT_SYSTEM_ACCOUNT {
			_, isMemResolver := ar.(*MemAccResolver)
			if v, ok := s.accounts.Load(s.opts.SystemAccount); !isMemResolver && ok && v.(*Account).claimJWT == "" {
				s.Noticef("Using bootstrapping system account")
				s.startGoRoutine(func() {
					defer s.grWG.Done()
					t := time.NewTicker(time.Second)
					defer t.Stop()
					for {
						select {
						case <-s.quitCh:
							return
						case <-t.C:
							if _, err := fetchAccount(ar, s.opts.SystemAccount); err != nil {
								continue
							}
							if _, err := s.fetchAccount(s.opts.SystemAccount); err != nil {
								continue
							}
							s.Noticef("System account fetched and updated")
							return
						}
					}
				})
			}
		}
	}

	// Start expiration of mapped GW replies, regardless if
	// this server is configured with gateway or not.
	s.startGWReplyMapExpiration()

	// Check if JetStream has been enabled. This needs to be after
	// the system account setup above. JetStream will create its
	// own system account if one is not present.
	if opts.JetStream {
		// Make sure someone is not trying to enable on the system account.
		if sa := s.SystemAccount(); sa != nil && sa.jsLimits != nil {
			s.Fatalf("Not allowed to enable JetStream on the system account")
		}
		cfg := &JetStreamConfig{
			StoreDir:  opts.StoreDir,
			MaxMemory: opts.JetStreamMaxMemory,
			MaxStore:  opts.JetStreamMaxStore,
			Domain:    opts.JetStreamDomain,
		}
		if err := s.EnableJetStream(cfg); err != nil {
			s.Fatalf("Can't start JetStream: %v", err)
			return
		}
	} else {
		// Check to see if any configured accounts have JetStream enabled.
		s.accounts.Range(func(k, v interface{}) bool {
			acc := v.(*Account)
			acc.mu.RLock()
			hasJs := acc.jsLimits != nil
			acc.mu.RUnlock()
			if hasJs {
				s.checkJetStreamExports()
				acc.enableAllJetStreamServiceImportsAndMappings()
			}
			return true
		})
	}

	// Start OCSP Stapling monitoring for TLS certificates if enabled.
	s.startOCSPMonitoring()

	// Start monitoring if needed.
	if err := s.StartMonitoring(); err != nil {
		s.Fatalf("Can't start monitoring: %v", err)
		return
	}

	// Start up gateway if needed. Do this before starting the routes, because
	// we want to resolve the gateway host:port so that this information can
	// be sent to other routes.
	if opts.Gateway.Port != 0 {
		s.startGateways()
	}

	// Start websocket server if needed. Do this before starting the routes, and
	// leaf node because we want to resolve the gateway host:port so that this
	// information can be sent to other routes.
	if opts.Websocket.Port != 0 {
		s.startWebsocketServer()
	}

	// Start up listen if we want to accept leaf node connections.
	if opts.LeafNode.Port != 0 {
		// Will resolve or assign the advertise address for the leafnode listener.
		// We need that in StartRouting().
		s.startLeafNodeAcceptLoop()
	}

	// Solicit remote servers for leaf node connections.
	if len(opts.LeafNode.Remotes) > 0 {
		s.solicitLeafNodeRemotes(opts.LeafNode.Remotes)
	}

	// TODO (ik): I wanted to refactor this by starting the client
	// accept loop first, that is, it would resolve listen spec
	// in place, but start the accept-for-loop in a different go
	// routine. This would get rid of the synchronization between
	// this function and StartRouting, which I also would have wanted
	// to refactor, but both AcceptLoop() and StartRouting() have
	// been exported and not sure if that would break users using them.
	// We could mark them as deprecated and remove in a release or two...

	// The Routing routine needs to wait for the client listen
	// port to be opened and potential ephemeral port selected.
	clientListenReady := make(chan struct{})

	// MQTT
	if opts.MQTT.Port != 0 {
		s.startMQTT()
	}

	// Start up routing as well if needed.
	if opts.Cluster.Port != 0 {
		s.startGoRoutine(func() {
			s.StartRouting(clientListenReady)
		})
	}

	// Pprof http endpoint for the profiler.
	if opts.ProfPort != 0 {
		s.StartProfiler()
	}

	if opts.PortsFileDir != _EMPTY_ {
		s.logPorts()
	}

	// Wait for clients.
	s.AcceptLoop(clientListenReady)
}

// Shutdown will shutdown the server instance by kicking out the AcceptLoop
// and closing all associated clients.
func (s *Server) Shutdown() {
	if s == nil {
		return
	}
	// Transfer off any raft nodes that we are a leader by shutting them all down.
	s.shutdownRaftNodes()

	// This is for clustered JetStream and ephemeral consumers.
	// No-op if not clustered or not running JetStream.
	s.migrateEphemerals()

	// Shutdown the eventing system as needed.
	// This is done first to send out any messages for
	// account status. We will also clean up any
	// eventing items associated with accounts.
	s.shutdownEventing()

	s.mu.Lock()
	// Prevent issues with multiple calls.
	if s.shutdown {
		s.mu.Unlock()
		return
	}
	s.Noticef("Initiating Shutdown...")

	accRes := s.accResolver

	opts := s.getOpts()

	s.shutdown = true
	s.running = false
	s.grMu.Lock()
	s.grRunning = false
	s.grMu.Unlock()
	s.mu.Unlock()

	if accRes != nil {
		accRes.Close()
	}

	// Now check jetstream.
	s.shutdownJetStream()

	s.mu.Lock()
	conns := make(map[uint64]*client)

	// Copy off the clients
	for i, c := range s.clients {
		conns[i] = c
	}
	// Copy off the connections that are not yet registered
	// in s.routes, but for which the readLoop has started
	s.grMu.Lock()
	for i, c := range s.grTmpClients {
		conns[i] = c
	}
	s.grMu.Unlock()
	// Copy off the routes
	for i, r := range s.routes {
		conns[i] = r
	}
	// Copy off the gateways
	s.getAllGatewayConnections(conns)

	// Copy off the leaf nodes
	for i, c := range s.leafs {
		conns[i] = c
	}

	// Number of done channel responses we expect.
	doneExpected := 0

	// Kick client AcceptLoop()
	if s.listener != nil {
		doneExpected++
		s.listener.Close()
		s.listener = nil
	}

	// Kick websocket server
	if s.websocket.server != nil {
		doneExpected++
		s.websocket.server.Close()
		s.websocket.server = nil
		s.websocket.listener = nil
	}

	// Kick MQTT accept loop
	if s.mqtt.listener != nil {
		doneExpected++
		s.mqtt.listener.Close()
		s.mqtt.listener = nil
	}

	// Kick leafnodes AcceptLoop()
	if s.leafNodeListener != nil {
		doneExpected++
		s.leafNodeListener.Close()
		s.leafNodeListener = nil
	}

	// Kick route AcceptLoop()
	if s.routeListener != nil {
		doneExpected++
		s.routeListener.Close()
		s.routeListener = nil
	}

	// Kick Gateway AcceptLoop()
	if s.gatewayListener != nil {
		doneExpected++
		s.gatewayListener.Close()
		s.gatewayListener = nil
	}

	// Kick HTTP monitoring if its running
	if s.http != nil {
		doneExpected++
		s.http.Close()
		s.http = nil
	}

	// Kick Profiling if its running
	if s.profiler != nil {
		doneExpected++
		s.profiler.Close()
	}

	s.mu.Unlock()

	// Release go routines that wait on that channel
	close(s.quitCh)

	// Close client and route connections
	for _, c := range conns {
		c.setNoReconnect()
		c.closeConnection(ServerShutdown)
	}

	// Block until the accept loops exit
	for doneExpected > 0 {
		<-s.done
		doneExpected--
	}

	// Wait for go routines to be done.
	s.grWG.Wait()

	if opts.PortsFileDir != _EMPTY_ {
		s.deletePortsFile(opts.PortsFileDir)
	}

	s.Noticef("Server Exiting..")
	// Close logger if applicable. It allows tests on Windows
	// to be able to do proper cleanup (delete log file).
	s.logging.RLock()
	log := s.logging.logger
	s.logging.RUnlock()
	if log != nil {
		if l, ok := log.(*logger.Logger); ok {
			l.Close()
		}
	}
	// Notify that the shutdown is complete
	close(s.shutdownComplete)
}

// WaitForShutdown will block until the server has been fully shutdown.
func (s *Server) WaitForShutdown() {
	<-s.shutdownComplete
}

// AcceptLoop is exported for easier testing.
func (s *Server) AcceptLoop(clr chan struct{}) {
	// If we were to exit before the listener is setup properly,
	// make sure we close the channel.
	defer func() {
		if clr != nil {
			close(clr)
		}
	}()

	// Snapshot server options.
	opts := s.getOpts()

	// Setup state that can enable shutdown
	s.mu.Lock()
	if s.shutdown {
		s.mu.Unlock()
		return
	}

	hp := net.JoinHostPort(opts.Host, strconv.Itoa(opts.Port))
	l, e := natsListen("tcp", hp)
	s.listenerErr = e
	if e != nil {
		s.mu.Unlock()
		s.Fatalf("Error listening on port: %s, %q", hp, e)
		return
	}
	s.Noticef("Listening for client connections on %s",
		net.JoinHostPort(opts.Host, strconv.Itoa(l.Addr().(*net.TCPAddr).Port)))

	// Alert of TLS enabled.
	if opts.TLSConfig != nil {
		s.Noticef("TLS required for client connections")
	}

	// If server was started with RANDOM_PORT (-1), opts.Port would be equal
	// to 0 at the beginning this function. So we need to get the actual port
	if opts.Port == 0 {
		// Write resolved port back to options.
		opts.Port = l.Addr().(*net.TCPAddr).Port
	}

	// Now that port has been set (if it was set to RANDOM), set the
	// server's info Host/Port with either values from Options or
	// ClientAdvertise.
	if err := s.setInfoHostPort(); err != nil {
		s.Fatalf("Error setting server INFO with ClientAdvertise value of %s, err=%v", s.opts.ClientAdvertise, err)
		l.Close()
		s.mu.Unlock()
		return
	}
	// Keep track of client connect URLs. We may need them later.
	s.clientConnectURLs = s.getClientConnectURLs()
	s.listener = l

	go s.acceptConnections(l, "Client", func(conn net.Conn) { s.createClient(conn) },
		func(_ error) bool {
			if s.isLameDuckMode() {
				// Signal that we are not accepting new clients
				s.ldmCh <- true
				// Now wait for the Shutdown...
				<-s.quitCh
				return true
			}
			return false
		})
	s.mu.Unlock()

	// Let the caller know that we are ready
	close(clr)
	clr = nil
}

func (s *Server) acceptConnections(l net.Listener, acceptName string, createFunc func(conn net.Conn), errFunc func(err error) bool) {
	tmpDelay := ACCEPT_MIN_SLEEP

	for {
		conn, err := l.Accept()
		if err != nil {
			if errFunc != nil && errFunc(err) {
				return
			}
			if tmpDelay = s.acceptError(acceptName, err, tmpDelay); tmpDelay < 0 {
				break
			}
			continue
		}
		tmpDelay = ACCEPT_MIN_SLEEP
		if !s.startGoRoutine(func() {
			createFunc(conn)
			s.grWG.Done()
		}) {
			conn.Close()
		}
	}
	s.Debugf(acceptName + " accept loop exiting..")
	s.done <- true
}

// This function sets the server's info Host/Port based on server Options.
// Note that this function may be called during config reload, this is why
// Host/Port may be reset to original Options if the ClientAdvertise option
// is not set (since it may have previously been).
func (s *Server) setInfoHostPort() error {
	// When this function is called, opts.Port is set to the actual listen
	// port (if option was originally set to RANDOM), even during a config
	// reload. So use of s.opts.Port is safe.
	if s.opts.ClientAdvertise != _EMPTY_ {
		h, p, err := parseHostPort(s.opts.ClientAdvertise, s.opts.Port)
		if err != nil {
			return err
		}
		s.info.Host = h
		s.info.Port = p
	} else {
		s.info.Host = s.opts.Host
		s.info.Port = s.opts.Port
	}
	return nil
}

// StartProfiler is called to enable dynamic profiling.
func (s *Server) StartProfiler() {
	// Snapshot server options.
	opts := s.getOpts()

	port := opts.ProfPort

	// Check for Random Port
	if port == -1 {
		port = 0
	}

	s.mu.Lock()
	if s.shutdown {
		s.mu.Unlock()
		return
	}
	hp := net.JoinHostPort(opts.Host, strconv.Itoa(port))

	l, err := net.Listen("tcp", hp)

	if err != nil {
		s.mu.Unlock()
		s.Fatalf("error starting profiler: %s", err)
		return
	}
	s.Noticef("profiling port: %d", l.Addr().(*net.TCPAddr).Port)

	srv := &http.Server{
		Addr:           hp,
		Handler:        http.DefaultServeMux,
		MaxHeaderBytes: 1 << 20,
	}
	s.profiler = l
	s.profilingServer = srv

	// Enable blocking profile
	runtime.SetBlockProfileRate(1)

	go func() {
		// if this errors out, it's probably because the server is being shutdown
		err := srv.Serve(l)
		if err != nil {
			s.mu.Lock()
			shutdown := s.shutdown
			s.mu.Unlock()
			if !shutdown {
				s.Fatalf("error starting profiler: %s", err)
			}
		}
		srv.Close()
		s.done <- true
	}()
	s.mu.Unlock()
}

// StartHTTPMonitoring will enable the HTTP monitoring port.
// DEPRECATED: Should use StartMonitoring.
func (s *Server) StartHTTPMonitoring() {
	s.startMonitoring(false)
}

// StartHTTPSMonitoring will enable the HTTPS monitoring port.
// DEPRECATED: Should use StartMonitoring.
func (s *Server) StartHTTPSMonitoring() {
	s.startMonitoring(true)
}

// StartMonitoring starts the HTTP or HTTPs server if needed.
func (s *Server) StartMonitoring() error {
	// Snapshot server options.
	opts := s.getOpts()

	// Specifying both HTTP and HTTPS ports is a misconfiguration
	if opts.HTTPPort != 0 && opts.HTTPSPort != 0 {
		return fmt.Errorf("can't specify both HTTP (%v) and HTTPs (%v) ports", opts.HTTPPort, opts.HTTPSPort)
	}
	var err error
	if opts.HTTPPort != 0 {
		err = s.startMonitoring(false)
	} else if opts.HTTPSPort != 0 {
		if opts.TLSConfig == nil {
			return fmt.Errorf("TLS cert and key required for HTTPS")
		}
		err = s.startMonitoring(true)
	}
	return err
}

// HTTP endpoints
const (
	RootPath     = "/"
	VarzPath     = "/varz"
	ConnzPath    = "/connz"
	RoutezPath   = "/routez"
	GatewayzPath = "/gatewayz"
	LeafzPath    = "/leafz"
	SubszPath    = "/subsz"
	StackszPath  = "/stacksz"
	AccountzPath = "/accountz"
	JszPath      = "/jsz"
)

func (s *Server) basePath(p string) string {
	return path.Join(s.httpBasePath, p)
}

// Start the monitoring server
func (s *Server) startMonitoring(secure bool) error {
	// Snapshot server options.
	opts := s.getOpts()

	var (
		hp           string
		err          error
		httpListener net.Listener
		port         int
	)

	monitorProtocol := "http"

	if secure {
		monitorProtocol += "s"
		port = opts.HTTPSPort
		if port == -1 {
			port = 0
		}
		hp = net.JoinHostPort(opts.HTTPHost, strconv.Itoa(port))
		config := opts.TLSConfig.Clone()
		config.ClientAuth = tls.NoClientCert
		httpListener, err = tls.Listen("tcp", hp, config)

	} else {
		port = opts.HTTPPort
		if port == -1 {
			port = 0
		}
		hp = net.JoinHostPort(opts.HTTPHost, strconv.Itoa(port))
		httpListener, err = net.Listen("tcp", hp)
	}

	if err != nil {
		return fmt.Errorf("can't listen to the monitor port: %v", err)
	}

	s.Noticef("Starting %s monitor on %s", monitorProtocol,
		net.JoinHostPort(opts.HTTPHost, strconv.Itoa(httpListener.Addr().(*net.TCPAddr).Port)))

	mux := http.NewServeMux()

	// Root
	mux.HandleFunc(s.basePath(RootPath), s.HandleRoot)
	// Varz
	mux.HandleFunc(s.basePath(VarzPath), s.HandleVarz)
	// Connz
	mux.HandleFunc(s.basePath(ConnzPath), s.HandleConnz)
	// Routez
	mux.HandleFunc(s.basePath(RoutezPath), s.HandleRoutez)
	// Gatewayz
	mux.HandleFunc(s.basePath(GatewayzPath), s.HandleGatewayz)
	// Leafz
	mux.HandleFunc(s.basePath(LeafzPath), s.HandleLeafz)
	// Subz
	mux.HandleFunc(s.basePath(SubszPath), s.HandleSubsz)
	// Subz alias for backwards compatibility
	mux.HandleFunc(s.basePath("/subscriptionsz"), s.HandleSubsz)
	// Stacksz
	mux.HandleFunc(s.basePath(StackszPath), s.HandleStacksz)
	// Accountz
	mux.HandleFunc(s.basePath(AccountzPath), s.HandleAccountz)
	// Jsz
	mux.HandleFunc(s.basePath(JszPath), s.HandleJsz)
	// Do not set a WriteTimeout because it could cause cURL/browser
	// to return empty response or unable to display page if the
	// server needs more time to build the response.
	srv := &http.Server{
		Addr:           hp,
		Handler:        mux,
		MaxHeaderBytes: 1 << 20,
	}
	s.mu.Lock()
	if s.shutdown {
		httpListener.Close()
		s.mu.Unlock()
		return nil
	}
	s.http = httpListener
	s.httpHandler = mux
	s.monitoringServer = srv
	s.mu.Unlock()

	go func() {
		if err := srv.Serve(httpListener); err != nil {
			s.mu.Lock()
			shutdown := s.shutdown
			s.mu.Unlock()
			if !shutdown {
				s.Fatalf("Error starting monitor on %q: %v", hp, err)
			}
		}
		srv.Close()
		srv.Handler = nil
		s.mu.Lock()
		s.httpHandler = nil
		s.mu.Unlock()
		s.done <- true
	}()

	return nil
}

// HTTPHandler returns the http.Handler object used to handle monitoring
// endpoints. It will return nil if the server is not configured for
// monitoring, or if the server has not been started yet (Server.Start()).
func (s *Server) HTTPHandler() http.Handler {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.httpHandler
}

// Perform a conditional deep copy due to reference nature of [Client|WS]ConnectURLs.
// If updates are made to Info, this function should be consulted and updated.
// Assume lock is held.
func (s *Server) copyInfo() Info {
	info := s.info
	if len(info.ClientConnectURLs) > 0 {
		info.ClientConnectURLs = append([]string(nil), s.info.ClientConnectURLs...)
	}
	if len(info.WSConnectURLs) > 0 {
		info.WSConnectURLs = append([]string(nil), s.info.WSConnectURLs...)
	}
	return info
}

// tlsMixConn is used when we can receive both TLS and non-TLS connections on same port.
type tlsMixConn struct {
	net.Conn
	pre *bytes.Buffer
}

// Read for our mixed multi-reader.
func (c *tlsMixConn) Read(b []byte) (int, error) {
	if c.pre != nil {
		n, err := c.pre.Read(b)
		if c.pre.Len() == 0 {
			c.pre = nil
		}
		return n, err
	}
	return c.Conn.Read(b)
}

func (s *Server) createClient(conn net.Conn) *client {
	// Snapshot server options.
	opts := s.getOpts()

	maxPay := int32(opts.MaxPayload)
	maxSubs := int32(opts.MaxSubs)
	// For system, maxSubs of 0 means unlimited, so re-adjust here.
	if maxSubs == 0 {
		maxSubs = -1
	}
	now := time.Now().UTC()

	c := &client{srv: s, nc: conn, opts: defaultOpts, mpay: maxPay, msubs: maxSubs, start: now, last: now}

	c.registerWithAccount(s.globalAccount())

	var info Info
	var authRequired bool

	s.mu.Lock()
	// Grab JSON info string
	info = s.copyInfo()
	if s.nonceRequired() {
		// Nonce handling
		var raw [nonceLen]byte
		nonce := raw[:]
		s.generateNonce(nonce)
		info.Nonce = string(nonce)
	}
	c.nonce = []byte(info.Nonce)
	authRequired = info.AuthRequired

	s.totalClients++
	s.mu.Unlock()

	// Grab lock
	c.mu.Lock()
	if authRequired {
		c.flags.set(expectConnect)
	}

	// Initialize
	c.initClient()

	c.Debugf("Client connection created")

	// Send our information.
	// Need to be sent in place since writeLoop cannot be started until
	// TLS handshake is done (if applicable).
	c.sendProtoNow(c.generateClientInfoJSON(info))

	// Unlock to register
	c.mu.Unlock()

	// Register with the server.
	s.mu.Lock()
	// If server is not running, Shutdown() may have already gathered the
	// list of connections to close. It won't contain this one, so we need
	// to bail out now otherwise the readLoop started down there would not
	// be interrupted. Skip also if in lame duck mode.
	if !s.running || s.ldm {
		// There are some tests that create a server but don't start it,
		// and use "async" clients and perform the parsing manually. Such
		// clients would branch here (since server is not running). However,
		// when a server was really running and has been shutdown, we must
		// close this connection.
		if s.shutdown {
			conn.Close()
		}
		s.mu.Unlock()
		return c
	}

	// If there is a max connections specified, check that adding
	// this new client would not push us over the max
	if opts.MaxConn > 0 && len(s.clients) >= opts.MaxConn {
		s.mu.Unlock()
		c.maxConnExceeded()
		return nil
	}
	s.clients[c.cid] = c

	tlsRequired := info.TLSRequired
	s.mu.Unlock()

	// Re-Grab lock
	c.mu.Lock()

	// Connection could have been closed while sending the INFO proto.
	isClosed := c.isClosed()

	var pre []byte
	// If we have both TLS and non-TLS allowed we need to see which
	// one the client wants.
	if !isClosed && opts.TLSConfig != nil && opts.AllowNonTLS {
		pre = make([]byte, 4)
		c.nc.SetReadDeadline(time.Now().Add(secondsToDuration(opts.TLSTimeout)))
		n, _ := io.ReadFull(c.nc, pre[:])
		c.nc.SetReadDeadline(time.Time{})
		pre = pre[:n]
		if n > 0 && pre[0] == 0x16 {
			tlsRequired = true
		} else {
			tlsRequired = false
		}
	}

	// Check for TLS
	if !isClosed && tlsRequired {
		// If we have a prebuffer create a multi-reader.
		if len(pre) > 0 {
			c.nc = &tlsMixConn{c.nc, bytes.NewBuffer(pre)}
			// Clear pre so it is not parsed.
			pre = nil
		}
		// Performs server-side TLS handshake.
		if err := c.doTLSServerHandshake(_EMPTY_, opts.TLSConfig, opts.TLSTimeout, opts.TLSPinnedCerts); err != nil {
			c.mu.Unlock()
			return nil
		}
	}

	// If connection is marked as closed, bail out.
	if isClosed {
		c.mu.Unlock()
		// Connection could have been closed due to TLS timeout or while trying
		// to send the INFO protocol. We need to call closeConnection() to make
		// sure that proper cleanup is done.
		c.closeConnection(WriteError)
		return nil
	}

	// Check for Auth. We schedule this timer after the TLS handshake to avoid
	// the race where the timer fires during the handshake and causes the
	// server to write bad data to the socket. See issue #432.
	if authRequired {
		c.setAuthTimer(secondsToDuration(opts.AuthTimeout))
	}

	// Do final client initialization

	// Set the Ping timer. Will be reset once connect was received.
	c.setPingTimer()

	// Spin up the read loop.
	s.startGoRoutine(func() { c.readLoop(pre) })

	// Spin up the write loop.
	s.startGoRoutine(func() { c.writeLoop() })

	if tlsRequired {
		c.Debugf("TLS handshake complete")
		cs := c.nc.(*tls.Conn).ConnectionState()
		c.Debugf("TLS version %s, cipher suite %s", tlsVersion(cs.Version), tlsCipher(cs.CipherSuite))
	}

	c.mu.Unlock()

	return c
}

// This will save off a closed client in a ring buffer such that
// /connz can inspect. Useful for debugging, etc.
func (s *Server) saveClosedClient(c *client, nc net.Conn, reason ClosedState) {
	now := time.Now().UTC()

	s.accountDisconnectEvent(c, now, reason.String())

	c.mu.Lock()

	cc := &closedClient{}
	cc.fill(c, nc, now)
	cc.Stop = &now
	cc.Reason = reason.String()

	// Do subs, do not place by default in main ConnInfo
	if len(c.subs) > 0 {
		cc.subs = make([]SubDetail, 0, len(c.subs))
		for _, sub := range c.subs {
			cc.subs = append(cc.subs, newSubDetail(sub))
		}
	}
	// Hold user as well.
	cc.user = c.opts.Username
	// Hold account name if not the global account.
	if c.acc != nil && c.acc.Name != globalAccountName {
		cc.acc = c.acc.Name
	}
	cc.JWT = c.opts.JWT
	cc.IssuerKey = issuerForClient(c)
	cc.Tags = c.tags
	cc.NameTag = c.nameTag
	c.mu.Unlock()

	// Place in the ring buffer
	s.mu.Lock()
	if s.closed != nil {
		s.closed.append(cc)
	}
	s.mu.Unlock()
}

// Adds to the list of client and websocket clients connect URLs.
// If there was a change, an INFO protocol is sent to registered clients
// that support async INFO protocols.
func (s *Server) addConnectURLsAndSendINFOToClients(curls, wsurls []string) {
	s.updateServerINFOAndSendINFOToClients(curls, wsurls, true)
}

// Removes from the list of client and websocket clients connect URLs.
// If there was a change, an INFO protocol is sent to registered clients
// that support async INFO protocols.
func (s *Server) removeConnectURLsAndSendINFOToClients(curls, wsurls []string) {
	s.updateServerINFOAndSendINFOToClients(curls, wsurls, false)
}

// Updates the list of client and websocket clients connect URLs and if any change
// sends an async INFO update to clients that support it.
func (s *Server) updateServerINFOAndSendINFOToClients(curls, wsurls []string, add bool) {
	s.mu.Lock()
	defer s.mu.Unlock()

	remove := !add
	// Will return true if we need alter the server's Info object.
	updateMap := func(urls []string, m refCountedUrlSet) bool {
		wasUpdated := false
		for _, url := range urls {
			if add && m.addUrl(url) {
				wasUpdated = true
			} else if remove && m.removeUrl(url) {
				wasUpdated = true
			}
		}
		return wasUpdated
	}
	cliUpdated := updateMap(curls, s.clientConnectURLsMap)
	wsUpdated := updateMap(wsurls, s.websocket.connectURLsMap)

	updateInfo := func(infoURLs *[]string, urls []string, m refCountedUrlSet) {
		// Recreate the info's slice from the map
		*infoURLs = (*infoURLs)[:0]
		// Add this server client connect ULRs first...
		*infoURLs = append(*infoURLs, urls...)
		// Then the ones from the map
		for url := range m {
			*infoURLs = append(*infoURLs, url)
		}
	}
	if cliUpdated {
		updateInfo(&s.info.ClientConnectURLs, s.clientConnectURLs, s.clientConnectURLsMap)
	}
	if wsUpdated {
		updateInfo(&s.info.WSConnectURLs, s.websocket.connectURLs, s.websocket.connectURLsMap)
	}
	if cliUpdated || wsUpdated {
		// Update the time of this update
		s.lastCURLsUpdate = time.Now().UnixNano()
		// Send to all registered clients that support async INFO protocols.
		s.sendAsyncInfoToClients(cliUpdated, wsUpdated)
	}
}

// Handle closing down a connection when the handshake has timedout.
func tlsTimeout(c *client, conn *tls.Conn) {
	c.mu.Lock()
	closed := c.isClosed()
	c.mu.Unlock()
	// Check if already closed
	if closed {
		return
	}
	cs := conn.ConnectionState()
	if !cs.HandshakeComplete {
		c.Errorf("TLS handshake timeout")
		c.sendErr("Secure Connection - TLS Required")
		c.closeConnection(TLSHandshakeError)
	}
}

// Seems silly we have to write these
func tlsVersion(ver uint16) string {
	switch ver {
	case tls.VersionTLS10:
		return "1.0"
	case tls.VersionTLS11:
		return "1.1"
	case tls.VersionTLS12:
		return "1.2"
	case tls.VersionTLS13:
		return "1.3"
	}
	return fmt.Sprintf("Unknown [0x%x]", ver)
}

// We use hex here so we don't need multiple versions
func tlsCipher(cs uint16) string {
	name, present := cipherMapByID[cs]
	if present {
		return name
	}
	return fmt.Sprintf("Unknown [0x%x]", cs)
}

// Remove a client or route from our internal accounting.
func (s *Server) removeClient(c *client) {
	// kind is immutable, so can check without lock
	switch c.kind {
	case CLIENT:
		c.mu.Lock()
		cid := c.cid
		updateProtoInfoCount := false
		if c.kind == CLIENT && c.opts.Protocol >= ClientProtoInfo {
			updateProtoInfoCount = true
		}
		c.mu.Unlock()

		s.mu.Lock()
		delete(s.clients, cid)
		if updateProtoInfoCount {
			s.cproto--
		}
		s.mu.Unlock()
	case ROUTER:
		s.removeRoute(c)
	case GATEWAY:
		s.removeRemoteGatewayConnection(c)
	case LEAF:
		s.removeLeafNodeConnection(c)
	}
}

func (s *Server) removeFromTempClients(cid uint64) {
	s.grMu.Lock()
	delete(s.grTmpClients, cid)
	s.grMu.Unlock()
}

func (s *Server) addToTempClients(cid uint64, c *client) bool {
	added := false
	s.grMu.Lock()
	if s.grRunning {
		s.grTmpClients[cid] = c
		added = true
	}
	s.grMu.Unlock()
	return added
}

/////////////////////////////////////////////////////////////////
// These are some helpers for accounting in functional tests.
/////////////////////////////////////////////////////////////////

// NumRoutes will report the number of registered routes.
func (s *Server) NumRoutes() int {
	s.mu.Lock()
	nr := len(s.routes)
	s.mu.Unlock()
	return nr
}

// NumRemotes will report number of registered remotes.
func (s *Server) NumRemotes() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return len(s.remotes)
}

// NumLeafNodes will report number of leaf node connections.
func (s *Server) NumLeafNodes() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return len(s.leafs)
}

// NumClients will report the number of registered clients.
func (s *Server) NumClients() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return len(s.clients)
}

// GetClient will return the client associated with cid.
func (s *Server) GetClient(cid uint64) *client {
	return s.getClient(cid)
}

// getClient will return the client associated with cid.
func (s *Server) getClient(cid uint64) *client {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.clients[cid]
}

// GetLeafNode returns the leafnode associated with the cid.
func (s *Server) GetLeafNode(cid uint64) *client {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.leafs[cid]
}

// NumSubscriptions will report how many subscriptions are active.
func (s *Server) NumSubscriptions() uint32 {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.numSubscriptions()
}

// numSubscriptions will report how many subscriptions are active.
// Lock should be held.
func (s *Server) numSubscriptions() uint32 {
	var subs int
	s.accounts.Range(func(k, v interface{}) bool {
		acc := v.(*Account)
		if acc.sl != nil {
			subs += acc.TotalSubs()
		}
		return true
	})
	return uint32(subs)
}

// NumSlowConsumers will report the number of slow consumers.
func (s *Server) NumSlowConsumers() int64 {
	return atomic.LoadInt64(&s.slowConsumers)
}

// ConfigTime will report the last time the server configuration was loaded.
func (s *Server) ConfigTime() time.Time {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.configTime
}

// Addr will return the net.Addr object for the current listener.
func (s *Server) Addr() net.Addr {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.listener == nil {
		return nil
	}
	return s.listener.Addr()
}

// MonitorAddr will return the net.Addr object for the monitoring listener.
func (s *Server) MonitorAddr() *net.TCPAddr {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.http == nil {
		return nil
	}
	return s.http.Addr().(*net.TCPAddr)
}

// ClusterAddr returns the net.Addr object for the route listener.
func (s *Server) ClusterAddr() *net.TCPAddr {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.routeListener == nil {
		return nil
	}
	return s.routeListener.Addr().(*net.TCPAddr)
}

// ProfilerAddr returns the net.Addr object for the profiler listener.
func (s *Server) ProfilerAddr() *net.TCPAddr {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.profiler == nil {
		return nil
	}
	return s.profiler.Addr().(*net.TCPAddr)
}

func (s *Server) readyForConnections(d time.Duration) error {
	// Snapshot server options.
	opts := s.getOpts()

	type info struct {
		ok  bool
		err error
	}
	chk := make(map[string]info)

	end := time.Now().Add(d)
	for time.Now().Before(end) {
		s.mu.Lock()
		chk["server"] = info{ok: s.listener != nil, err: s.listenerErr}
		chk["route"] = info{ok: (opts.Cluster.Port == 0 || s.routeListener != nil), err: s.routeListenerErr}
		chk["gateway"] = info{ok: (opts.Gateway.Name == "" || s.gatewayListener != nil), err: s.gatewayListenerErr}
		chk["leafNode"] = info{ok: (opts.LeafNode.Port == 0 || s.leafNodeListener != nil), err: s.leafNodeListenerErr}
		chk["websocket"] = info{ok: (opts.Websocket.Port == 0 || s.websocket.listener != nil), err: s.websocket.listenerErr}
		chk["mqtt"] = info{ok: (opts.MQTT.Port == 0 || s.mqtt.listener != nil), err: s.mqtt.listenerErr}
		s.mu.Unlock()

		var numOK int
		for _, inf := range chk {
			if inf.ok {
				numOK++
			}
		}
		if numOK == len(chk) {
			return nil
		}
		time.Sleep(25 * time.Millisecond)
	}

	failed := make([]string, 0, len(chk))
	for name, inf := range chk {
		if inf.ok && inf.err != nil {
			failed = append(failed, fmt.Sprintf("%s(ok, but %s)", name, inf.err))
		}
		if !inf.ok && inf.err == nil {
			failed = append(failed, name)
		}
		if !inf.ok && inf.err != nil {
			failed = append(failed, fmt.Sprintf("%s(%s)", name, inf.err))
		}
	}

	return fmt.Errorf(
		"failed to be ready for connections after %s: %s",
		d, strings.Join(failed, ", "),
	)
}

// ReadyForConnections returns `true` if the server is ready to accept clients
// and, if routing is enabled, route connections. If after the duration
// `dur` the server is still not ready, returns `false`.
func (s *Server) ReadyForConnections(dur time.Duration) bool {
	return s.readyForConnections(dur) == nil
}

// Quick utility to function to tell if the server supports headers.
func (s *Server) supportsHeaders() bool {
	if s == nil {
		return false
	}
	return !(s.getOpts().NoHeaderSupport)
}

// ID returns the server's ID
func (s *Server) ID() string {
	return s.info.ID
}

// NodeName returns the node name for this server.
func (s *Server) NodeName() string {
	return string(getHash(s.info.Name))
}

// Name returns the server's name. This will be the same as the ID if it was not set.
func (s *Server) Name() string {
	return s.info.Name
}

func (s *Server) String() string {
	return s.info.Name
}

func (s *Server) startGoRoutine(f func()) bool {
	var started bool
	s.grMu.Lock()
	if s.grRunning {
		s.grWG.Add(1)
		go f()
		started = true
	}
	s.grMu.Unlock()
	return started
}

func (s *Server) numClosedConns() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.closed.len()
}

func (s *Server) totalClosedConns() uint64 {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.closed.totalConns()
}

func (s *Server) closedClients() []*closedClient {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.closed.closedClients()
}

// getClientConnectURLs returns suitable URLs for clients to connect to the listen
// port based on the server options' Host and Port. If the Host corresponds to
// "any" interfaces, this call returns the list of resolved IP addresses.
// If ClientAdvertise is set, returns the client advertise host and port.
// The server lock is assumed held on entry.
func (s *Server) getClientConnectURLs() []string {
	// Snapshot server options.
	opts := s.getOpts()
	// Ignore error here since we know that if there is client advertise, the
	// parseHostPort is correct because we did it right before calling this
	// function in Server.New().
	urls, _ := s.getConnectURLs(opts.ClientAdvertise, opts.Host, opts.Port)
	return urls
}

// Generic version that will return an array of URLs based on the given
// advertise, host and port values.
func (s *Server) getConnectURLs(advertise, host string, port int) ([]string, error) {
	urls := make([]string, 0, 1)

	// short circuit if advertise is set
	if advertise != "" {
		h, p, err := parseHostPort(advertise, port)
		if err != nil {
			return nil, err
		}
		urls = append(urls, net.JoinHostPort(h, strconv.Itoa(p)))
	} else {
		sPort := strconv.Itoa(port)
		_, ips, err := s.getNonLocalIPsIfHostIsIPAny(host, true)
		for _, ip := range ips {
			urls = append(urls, net.JoinHostPort(ip, sPort))
		}
		if err != nil || len(urls) == 0 {
			// We are here if s.opts.Host is not "0.0.0.0" nor "::", or if for some
			// reason we could not add any URL in the loop above.
			// We had a case where a Windows VM was hosed and would have err == nil
			// and not add any address in the array in the loop above, and we
			// ended-up returning 0.0.0.0, which is problematic for Windows clients.
			// Check for 0.0.0.0 or :: specifically, and ignore if that's the case.
			if host == "0.0.0.0" || host == "::" {
				s.Errorf("Address %q can not be resolved properly", host)
			} else {
				urls = append(urls, net.JoinHostPort(host, sPort))
			}
		}
	}
	return urls, nil
}

// Returns an array of non local IPs if the provided host is
// 0.0.0.0 or ::. It returns the first resolved if `all` is
// false.
// The boolean indicate if the provided host was 0.0.0.0 (or ::)
// so that if the returned array is empty caller can decide
// what to do next.
func (s *Server) getNonLocalIPsIfHostIsIPAny(host string, all bool) (bool, []string, error) {
	ip := net.ParseIP(host)
	// If this is not an IP, we are done
	if ip == nil {
		return false, nil, nil
	}
	// If this is not 0.0.0.0 or :: we have nothing to do.
	if !ip.IsUnspecified() {
		return false, nil, nil
	}
	s.Debugf("Get non local IPs for %q", host)
	var ips []string
	ifaces, _ := net.Interfaces()
	for _, i := range ifaces {
		addrs, _ := i.Addrs()
		for _, addr := range addrs {
			switch v := addr.(type) {
			case *net.IPNet:
				ip = v.IP
			case *net.IPAddr:
				ip = v.IP
			}
			ipStr := ip.String()
			// Skip non global unicast addresses
			if !ip.IsGlobalUnicast() || ip.IsUnspecified() {
				ip = nil
				continue
			}
			s.Debugf("  ip=%s", ipStr)
			ips = append(ips, ipStr)
			if !all {
				break
			}
		}
	}
	return true, ips, nil
}

// if the ip is not specified, attempt to resolve it
func resolveHostPorts(addr net.Listener) []string {
	hostPorts := make([]string, 0)
	hp := addr.Addr().(*net.TCPAddr)
	port := strconv.Itoa(hp.Port)
	if hp.IP.IsUnspecified() {
		var ip net.IP
		ifaces, _ := net.Interfaces()
		for _, i := range ifaces {
			addrs, _ := i.Addrs()
			for _, addr := range addrs {
				switch v := addr.(type) {
				case *net.IPNet:
					ip = v.IP
					hostPorts = append(hostPorts, net.JoinHostPort(ip.String(), port))
				case *net.IPAddr:
					ip = v.IP
					hostPorts = append(hostPorts, net.JoinHostPort(ip.String(), port))
				default:
					continue
				}
			}
		}
	} else {
		hostPorts = append(hostPorts, net.JoinHostPort(hp.IP.String(), port))
	}
	return hostPorts
}

// format the address of a net.Listener with a protocol
func formatURL(protocol string, addr net.Listener) []string {
	hostports := resolveHostPorts(addr)
	for i, hp := range hostports {
		hostports[i] = fmt.Sprintf("%s://%s", protocol, hp)
	}
	return hostports
}

// Ports describes URLs that the server can be contacted in
type Ports struct {
	Nats       []string `json:"nats,omitempty"`
	Monitoring []string `json:"monitoring,omitempty"`
	Cluster    []string `json:"cluster,omitempty"`
	Profile    []string `json:"profile,omitempty"`
	WebSocket  []string `json:"websocket,omitempty"`
}

// PortsInfo attempts to resolve all the ports. If after maxWait the ports are not
// resolved, it returns nil. Otherwise it returns a Ports struct
// describing ports where the server can be contacted
func (s *Server) PortsInfo(maxWait time.Duration) *Ports {
	if s.readyForListeners(maxWait) {
		opts := s.getOpts()

		s.mu.Lock()
		tls := s.info.TLSRequired
		listener := s.listener
		httpListener := s.http
		clusterListener := s.routeListener
		profileListener := s.profiler
		wsListener := s.websocket.listener
		wss := s.websocket.tls
		s.mu.Unlock()

		ports := Ports{}

		if listener != nil {
			natsProto := "nats"
			if tls {
				natsProto = "tls"
			}
			ports.Nats = formatURL(natsProto, listener)
		}

		if httpListener != nil {
			monProto := "http"
			if opts.HTTPSPort != 0 {
				monProto = "https"
			}
			ports.Monitoring = formatURL(monProto, httpListener)
		}

		if clusterListener != nil {
			clusterProto := "nats"
			if opts.Cluster.TLSConfig != nil {
				clusterProto = "tls"
			}
			ports.Cluster = formatURL(clusterProto, clusterListener)
		}

		if profileListener != nil {
			ports.Profile = formatURL("http", profileListener)
		}

		if wsListener != nil {
			protocol := wsSchemePrefix
			if wss {
				protocol = wsSchemePrefixTLS
			}
			ports.WebSocket = formatURL(protocol, wsListener)
		}

		return &ports
	}

	return nil
}

// Returns the portsFile. If a non-empty dirHint is provided, the dirHint
// path is used instead of the server option value
func (s *Server) portFile(dirHint string) string {
	dirname := s.getOpts().PortsFileDir
	if dirHint != "" {
		dirname = dirHint
	}
	if dirname == _EMPTY_ {
		return _EMPTY_
	}
	return filepath.Join(dirname, fmt.Sprintf("%s_%d.ports", filepath.Base(os.Args[0]), os.Getpid()))
}

// Delete the ports file. If a non-empty dirHint is provided, the dirHint
// path is used instead of the server option value
func (s *Server) deletePortsFile(hintDir string) {
	portsFile := s.portFile(hintDir)
	if portsFile != "" {
		if err := os.Remove(portsFile); err != nil {
			s.Errorf("Error cleaning up ports file %s: %v", portsFile, err)
		}
	}
}

// Writes a file with a serialized Ports to the specified ports_file_dir.
// The name of the file is `exename_pid.ports`, typically nats-server_pid.ports.
// if ports file is not set, this function has no effect
func (s *Server) logPorts() {
	opts := s.getOpts()
	portsFile := s.portFile(opts.PortsFileDir)
	if portsFile != _EMPTY_ {
		go func() {
			info := s.PortsInfo(5 * time.Second)
			if info == nil {
				s.Errorf("Unable to resolve the ports in the specified time")
				return
			}
			data, err := json.Marshal(info)
			if err != nil {
				s.Errorf("Error marshaling ports file: %v", err)
				return
			}
			if err := ioutil.WriteFile(portsFile, data, 0666); err != nil {
				s.Errorf("Error writing ports file (%s): %v", portsFile, err)
				return
			}

		}()
	}
}

// waits until a calculated list of listeners is resolved or a timeout
func (s *Server) readyForListeners(dur time.Duration) bool {
	end := time.Now().Add(dur)
	for time.Now().Before(end) {
		s.mu.Lock()
		listeners := s.serviceListeners()
		s.mu.Unlock()
		if len(listeners) == 0 {
			return false
		}

		ok := true
		for _, l := range listeners {
			if l == nil {
				ok = false
				break
			}
		}
		if ok {
			return true
		}
		select {
		case <-s.quitCh:
			return false
		case <-time.After(25 * time.Millisecond):
			// continue - unable to select from quit - we are still running
		}
	}
	return false
}

// returns a list of listeners that are intended for the process
// if the entry is nil, the interface is yet to be resolved
func (s *Server) serviceListeners() []net.Listener {
	listeners := make([]net.Listener, 0)
	opts := s.getOpts()
	listeners = append(listeners, s.listener)
	if opts.Cluster.Port != 0 {
		listeners = append(listeners, s.routeListener)
	}
	if opts.HTTPPort != 0 || opts.HTTPSPort != 0 {
		listeners = append(listeners, s.http)
	}
	if opts.ProfPort != 0 {
		listeners = append(listeners, s.profiler)
	}
	if opts.Websocket.Port != 0 {
		listeners = append(listeners, s.websocket.listener)
	}
	return listeners
}

// Returns true if in lame duck mode.
func (s *Server) isLameDuckMode() bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.ldm
}

// This function will close the client listener then close the clients
// at some interval to avoid a reconnecting storm.
func (s *Server) lameDuckMode() {
	s.mu.Lock()
	// Check if there is actually anything to do
	if s.shutdown || s.ldm || s.listener == nil {
		s.mu.Unlock()
		return
	}
	s.Noticef("Entering lame duck mode, stop accepting new clients")
	s.ldm = true
	expected := 1
	s.listener.Close()
	s.listener = nil
	if s.websocket.server != nil {
		expected++
		s.websocket.server.Close()
		s.websocket.server = nil
		s.websocket.listener = nil
	}
	s.ldmCh = make(chan bool, expected)
	opts := s.getOpts()
	gp := opts.LameDuckGracePeriod
	// For tests, we want the grace period to be in some cases bigger
	// than the ldm duration, so to by-pass the validateOptions() check,
	// we use negative number and flip it here.
	if gp < 0 {
		gp *= -1
	}
	s.mu.Unlock()

	// If we are running any raftNodes transfer leaders.
	if hadTransfers := s.transferRaftLeaders(); hadTransfers {
		// They will tranfer leadership quickly, but wait here for a second.
		select {
		case <-time.After(time.Second):
		case <-s.quitCh:
			return
		}
	}

	// Wait for accept loops to be done to make sure that no new
	// client can connect
	for i := 0; i < expected; i++ {
		<-s.ldmCh
	}

	s.mu.Lock()
	// Need to recheck few things
	if s.shutdown || len(s.clients) == 0 {
		s.mu.Unlock()
		// If there is no client, we need to call Shutdown() to complete
		// the LDMode. If server has been shutdown while lock was released,
		// calling Shutdown() should be no-op.
		s.Shutdown()
		return
	}
	dur := int64(opts.LameDuckDuration)
	dur -= int64(gp)
	if dur <= 0 {
		dur = int64(time.Second)
	}
	numClients := int64(len(s.clients))
	batch := 1
	// Sleep interval between each client connection close.
	si := dur / numClients
	if si < 1 {
		// Should not happen (except in test with very small LD duration), but
		// if there are too many clients, batch the number of close and
		// use a tiny sleep interval that will result in yield likely.
		si = 1
		batch = int(numClients / dur)
	} else if si > int64(time.Second) {
		// Conversely, there is no need to sleep too long between clients
		// and spread say 10 clients for the 2min duration. Sleeping no
		// more than 1sec.
		si = int64(time.Second)
	}

	// Now capture all clients
	clients := make([]*client, 0, len(s.clients))
	for _, client := range s.clients {
		clients = append(clients, client)
	}
	// Now that we know that no new client can be accepted,
	// send INFO to routes and clients to notify this state.
	s.sendLDMToRoutes()
	s.sendLDMToClients()
	s.mu.Unlock()

	t := time.NewTimer(gp)
	// Delay start of closing of client connections in case
	// we have several servers that we want to signal to enter LD mode
	// and not have their client reconnect to each other.
	select {
	case <-t.C:
		s.Noticef("Closing existing clients")
	case <-s.quitCh:
		t.Stop()
		return
	}
	for i, client := range clients {
		client.closeConnection(ServerShutdown)
		if i == len(clients)-1 {
			break
		}
		if batch == 1 || i%batch == 0 {
			// We pick a random interval which will be at least si/2
			v := rand.Int63n(si)
			if v < si/2 {
				v = si / 2
			}
			t.Reset(time.Duration(v))
			// Sleep for given interval or bail out if kicked by Shutdown().
			select {
			case <-t.C:
			case <-s.quitCh:
				t.Stop()
				return
			}
		}
	}
	s.Shutdown()
}

// Send an INFO update to routes with the indication that this server is in LDM mode.
// Server lock is held on entry.
func (s *Server) sendLDMToRoutes() {
	s.routeInfo.LameDuckMode = true
	s.generateRouteInfoJSON()
	for _, r := range s.routes {
		r.mu.Lock()
		r.enqueueProto(s.routeInfoJSON)
		r.mu.Unlock()
	}
	// Clear now so that we notify only once, should we have to send other INFOs.
	s.routeInfo.LameDuckMode = false
}

// Send an INFO update to clients with the indication that this server is in
// LDM mode and with only URLs of other nodes.
// Server lock is held on entry.
func (s *Server) sendLDMToClients() {
	s.info.LameDuckMode = true
	// Clear this so that if there are further updates, we don't send our URLs.
	s.clientConnectURLs = s.clientConnectURLs[:0]
	if s.websocket.connectURLs != nil {
		s.websocket.connectURLs = s.websocket.connectURLs[:0]
	}
	// Reset content first.
	s.info.ClientConnectURLs = s.info.ClientConnectURLs[:0]
	s.info.WSConnectURLs = s.info.WSConnectURLs[:0]
	// Only add the other nodes if we are allowed to.
	if !s.getOpts().Cluster.NoAdvertise {
		for url := range s.clientConnectURLsMap {
			s.info.ClientConnectURLs = append(s.info.ClientConnectURLs, url)
		}
		for url := range s.websocket.connectURLsMap {
			s.info.WSConnectURLs = append(s.info.WSConnectURLs, url)
		}
	}
	// Send to all registered clients that support async INFO protocols.
	s.sendAsyncInfoToClients(true, true)
	// We now clear the info.LameDuckMode flag so that if there are
	// cluster updates and we send the INFO, we don't have the boolean
	// set which would cause multiple LDM notifications to clients.
	s.info.LameDuckMode = false
}

// If given error is a net.Error and is temporary, sleeps for the given
// delay and double it, but cap it to ACCEPT_MAX_SLEEP. The sleep is
// interrupted if the server is shutdown.
// An error message is displayed depending on the type of error.
// Returns the new (or unchanged) delay, or a negative value if the
// server has been or is being shutdown.
func (s *Server) acceptError(acceptName string, err error, tmpDelay time.Duration) time.Duration {
	if !s.isRunning() {
		return -1
	}
	if ne, ok := err.(net.Error); ok && ne.Temporary() {
		s.Errorf("Temporary %s Accept Error(%v), sleeping %dms", acceptName, ne, tmpDelay/time.Millisecond)
		select {
		case <-time.After(tmpDelay):
		case <-s.quitCh:
			return -1
		}
		tmpDelay *= 2
		if tmpDelay > ACCEPT_MAX_SLEEP {
			tmpDelay = ACCEPT_MAX_SLEEP
		}
	} else {
		s.Errorf("%s Accept error: %v", acceptName, err)
	}
	return tmpDelay
}

var errNoIPAvail = errors.New("no IP available")

func (s *Server) getRandomIP(resolver netResolver, url string, excludedAddresses map[string]struct{}) (string, error) {
	host, port, err := net.SplitHostPort(url)
	if err != nil {
		return "", err
	}
	// If already an IP, skip.
	if net.ParseIP(host) != nil {
		return url, nil
	}
	ips, err := resolver.LookupHost(context.Background(), host)
	if err != nil {
		return "", fmt.Errorf("lookup for host %q: %v", host, err)
	}
	if len(excludedAddresses) > 0 {
		for i := 0; i < len(ips); i++ {
			ip := ips[i]
			addr := net.JoinHostPort(ip, port)
			if _, excluded := excludedAddresses[addr]; excluded {
				if len(ips) == 1 {
					ips = nil
					break
				}
				ips[i] = ips[len(ips)-1]
				ips = ips[:len(ips)-1]
				i--
			}
		}
		if len(ips) == 0 {
			return "", errNoIPAvail
		}
	}
	var address string
	if len(ips) == 0 {
		s.Warnf("Unable to get IP for %s, will try with %s: %v", host, url, err)
		address = url
	} else {
		var ip string
		if len(ips) == 1 {
			ip = ips[0]
		} else {
			ip = ips[rand.Int31n(int32(len(ips)))]
		}
		// add the port
		address = net.JoinHostPort(ip, port)
	}
	return address, nil
}

// Returns true for the first attempt and depending on the nature
// of the attempt (first connect or a reconnect), when the number
// of attempts is equal to the configured report attempts.
func (s *Server) shouldReportConnectErr(firstConnect bool, attempts int) bool {
	opts := s.getOpts()
	if firstConnect {
		if attempts == 1 || attempts%opts.ConnectErrorReports == 0 {
			return true
		}
		return false
	}
	if attempts == 1 || attempts%opts.ReconnectErrorReports == 0 {
		return true
	}
	return false
}

// Invoked for route, leaf and gateway connections. Set the very first
// PING to a lower interval to capture the initial RTT.
// After that the PING interval will be set to the user defined value.
// Client lock should be held.
func (s *Server) setFirstPingTimer(c *client) {
	opts := s.getOpts()
	d := opts.PingInterval

	if !opts.DisableShortFirstPing {
		if c.kind != CLIENT {
			if d > firstPingInterval {
				d = firstPingInterval
			}
			if c.kind == GATEWAY {
				d = adjustPingIntervalForGateway(d)
			}
		} else if d > firstClientPingInterval {
			d = firstClientPingInterval
		}
	}
	// We randomize the first one by an offset up to 20%, e.g. 2m ~= max 24s.
	addDelay := rand.Int63n(int64(d / 5))
	d += time.Duration(addDelay)
	c.ping.tmr = time.AfterFunc(d, c.processPingTimer)
}

func (s *Server) updateRemoteSubscription(acc *Account, sub *subscription, delta int32) {
	s.updateRouteSubscriptionMap(acc, sub, delta)
	if s.gateway.enabled {
		s.gatewayUpdateSubInterest(acc.Name, sub, delta)
	}

	s.updateLeafNodes(acc, sub, delta)
}