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pool.go
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pool.go
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package pool
import (
"container/list"
"fmt"
"io"
"net"
"net/rpc"
"sync"
"sync/atomic"
"time"
"github.com/hashicorp/consul/lib"
"github.com/hashicorp/consul/tlsutil"
"github.com/hashicorp/net-rpc-msgpackrpc"
"github.com/hashicorp/yamux"
)
const defaultDialTimeout = 10 * time.Second
// muxSession is used to provide an interface for a stream multiplexer.
type muxSession interface {
Open() (net.Conn, error)
Close() error
}
// streamClient is used to wrap a stream with an RPC client
type StreamClient struct {
stream net.Conn
codec rpc.ClientCodec
}
func (sc *StreamClient) Close() {
sc.stream.Close()
sc.codec.Close()
}
// Conn is a pooled connection to a Consul server
type Conn struct {
refCount int32
shouldClose int32
addr net.Addr
session muxSession
lastUsed time.Time
version int
pool *ConnPool
clients *list.List
clientLock sync.Mutex
}
func (c *Conn) Close() error {
return c.session.Close()
}
// getClient is used to get a cached or new client
func (c *Conn) getClient() (*StreamClient, error) {
// Check for cached client
c.clientLock.Lock()
front := c.clients.Front()
if front != nil {
c.clients.Remove(front)
}
c.clientLock.Unlock()
if front != nil {
return front.Value.(*StreamClient), nil
}
// Open a new session
stream, err := c.session.Open()
if err != nil {
return nil, err
}
// Create the RPC client
codec := msgpackrpc.NewClientCodec(stream)
// Return a new stream client
sc := &StreamClient{
stream: stream,
codec: codec,
}
return sc, nil
}
// returnStream is used when done with a stream
// to allow re-use by a future RPC
func (c *Conn) returnClient(client *StreamClient) {
didSave := false
c.clientLock.Lock()
if c.clients.Len() < c.pool.MaxStreams && atomic.LoadInt32(&c.shouldClose) == 0 {
c.clients.PushFront(client)
didSave = true
// If this is a Yamux stream, shrink the internal buffers so that
// we can GC the idle memory
if ys, ok := client.stream.(*yamux.Stream); ok {
ys.Shrink()
}
}
c.clientLock.Unlock()
if !didSave {
client.Close()
}
}
// markForUse does all the bookkeeping required to ready a connection for use.
func (c *Conn) markForUse() {
c.lastUsed = time.Now()
atomic.AddInt32(&c.refCount, 1)
}
// ConnPool is used to maintain a connection pool to other Consul
// servers. This is used to reduce the latency of RPC requests between
// servers. It is only used to pool connections in the rpcConsul mode.
// Raft connections are pooled separately. Maintain at most one
// connection per host, for up to MaxTime. When MaxTime connection
// reaping is disabled. MaxStreams is used to control the number of idle
// streams allowed. If TLS settings are provided outgoing connections
// use TLS.
type ConnPool struct {
// SrcAddr is the source address for outgoing connections.
SrcAddr *net.TCPAddr
// LogOutput is used to control logging
LogOutput io.Writer
// The maximum time to keep a connection open
MaxTime time.Duration
// The maximum number of open streams to keep
MaxStreams int
// TLS wrapper
TLSWrapper tlsutil.DCWrapper
// ForceTLS is used to enforce outgoing TLS verification
ForceTLS bool
sync.Mutex
// pool maps an address to a open connection
pool map[string]*Conn
// limiter is used to throttle the number of connect attempts
// to a given address. The first thread will attempt a connection
// and put a channel in here, which all other threads will wait
// on to close.
limiter map[string]chan struct{}
// Used to indicate the pool is shutdown
shutdown bool
shutdownCh chan struct{}
// once initializes the internal data structures and connection
// reaping on first use.
once sync.Once
}
// init configures the initial data structures. It should be called
// by p.once.Do(p.init) in all public methods.
func (p *ConnPool) init() {
p.pool = make(map[string]*Conn)
p.limiter = make(map[string]chan struct{})
p.shutdownCh = make(chan struct{})
if p.MaxTime > 0 {
go p.reap()
}
}
// Shutdown is used to close the connection pool
func (p *ConnPool) Shutdown() error {
p.once.Do(p.init)
p.Lock()
defer p.Unlock()
for _, conn := range p.pool {
conn.Close()
}
p.pool = make(map[string]*Conn)
if p.shutdown {
return nil
}
p.shutdown = true
close(p.shutdownCh)
return nil
}
// acquire will return a pooled connection, if available. Otherwise it will
// wait for an existing connection attempt to finish, if one if in progress,
// and will return that one if it succeeds. If all else fails, it will return a
// newly-created connection and add it to the pool.
func (p *ConnPool) acquire(dc string, addr net.Addr, version int, useTLS bool) (*Conn, error) {
addrStr := addr.String()
// Check to see if there's a pooled connection available. This is up
// here since it should the the vastly more common case than the rest
// of the code here.
p.Lock()
c := p.pool[addrStr]
if c != nil {
c.markForUse()
p.Unlock()
return c, nil
}
// If not (while we are still locked), set up the throttling structure
// for this address, which will make everyone else wait until our
// attempt is done.
var wait chan struct{}
var ok bool
if wait, ok = p.limiter[addrStr]; !ok {
wait = make(chan struct{})
p.limiter[addrStr] = wait
}
isLeadThread := !ok
p.Unlock()
// If we are the lead thread, make the new connection and then wake
// everybody else up to see if we got it.
if isLeadThread {
c, err := p.getNewConn(dc, addr, version, useTLS)
p.Lock()
delete(p.limiter, addrStr)
close(wait)
if err != nil {
p.Unlock()
return nil, err
}
p.pool[addrStr] = c
p.Unlock()
return c, nil
}
// Otherwise, wait for the lead thread to attempt the connection
// and use what's in the pool at that point.
select {
case <-p.shutdownCh:
return nil, fmt.Errorf("rpc error: shutdown")
case <-wait:
}
// See if the lead thread was able to get us a connection.
p.Lock()
if c := p.pool[addrStr]; c != nil {
c.markForUse()
p.Unlock()
return c, nil
}
p.Unlock()
return nil, fmt.Errorf("rpc error: lead thread didn't get connection")
}
// HalfCloser is an interface that exposes a TCP half-close. We need this
// because we want to expose the raw TCP connection underlying a TLS one in a
// way that's hard to screw up and use for anything else. There's a change
// brewing that will allow us to use the TLS connection for this instead -
// https://go-review.googlesource.com/#/c/25159/.
type HalfCloser interface {
CloseWrite() error
}
// DialTimeout is used to establish a raw connection to the given server, with a
// given connection timeout.
func (p *ConnPool) DialTimeout(dc string, addr net.Addr, timeout time.Duration, useTLS bool) (net.Conn, HalfCloser, error) {
p.once.Do(p.init)
// Try to dial the conn
d := &net.Dialer{LocalAddr: p.SrcAddr, Timeout: timeout}
conn, err := d.Dial("tcp", addr.String())
if err != nil {
return nil, nil, err
}
// Cast to TCPConn
var hc HalfCloser
if tcp, ok := conn.(*net.TCPConn); ok {
tcp.SetKeepAlive(true)
tcp.SetNoDelay(true)
hc = tcp
}
// Check if TLS is enabled
if (useTLS || p.ForceTLS) && p.TLSWrapper != nil {
// Switch the connection into TLS mode
if _, err := conn.Write([]byte{byte(RPCTLS)}); err != nil {
conn.Close()
return nil, nil, err
}
// Wrap the connection in a TLS client
tlsConn, err := p.TLSWrapper(dc, conn)
if err != nil {
conn.Close()
return nil, nil, err
}
conn = tlsConn
}
return conn, hc, nil
}
// getNewConn is used to return a new connection
func (p *ConnPool) getNewConn(dc string, addr net.Addr, version int, useTLS bool) (*Conn, error) {
// Get a new, raw connection.
conn, _, err := p.DialTimeout(dc, addr, defaultDialTimeout, useTLS)
if err != nil {
return nil, err
}
// Switch the multiplexing based on version
var session muxSession
if version < 2 {
conn.Close()
return nil, fmt.Errorf("cannot make client connection, unsupported protocol version %d", version)
}
// Write the Consul multiplex byte to set the mode
if _, err := conn.Write([]byte{byte(RPCMultiplexV2)}); err != nil {
conn.Close()
return nil, err
}
// Setup the logger
conf := yamux.DefaultConfig()
conf.LogOutput = p.LogOutput
// Create a multiplexed session
session, _ = yamux.Client(conn, conf)
// Wrap the connection
c := &Conn{
refCount: 1,
addr: addr,
session: session,
clients: list.New(),
lastUsed: time.Now(),
version: version,
pool: p,
}
return c, nil
}
// clearConn is used to clear any cached connection, potentially in response to an error
func (p *ConnPool) clearConn(conn *Conn) {
// Ensure returned streams are closed
atomic.StoreInt32(&conn.shouldClose, 1)
// Clear from the cache
addrStr := conn.addr.String()
p.Lock()
if c, ok := p.pool[addrStr]; ok && c == conn {
delete(p.pool, addrStr)
}
p.Unlock()
// Close down immediately if idle
if refCount := atomic.LoadInt32(&conn.refCount); refCount == 0 {
conn.Close()
}
}
// releaseConn is invoked when we are done with a conn to reduce the ref count
func (p *ConnPool) releaseConn(conn *Conn) {
refCount := atomic.AddInt32(&conn.refCount, -1)
if refCount == 0 && atomic.LoadInt32(&conn.shouldClose) == 1 {
conn.Close()
}
}
// getClient is used to get a usable client for an address and protocol version
func (p *ConnPool) getClient(dc string, addr net.Addr, version int, useTLS bool) (*Conn, *StreamClient, error) {
retries := 0
START:
// Try to get a conn first
conn, err := p.acquire(dc, addr, version, useTLS)
if err != nil {
return nil, nil, fmt.Errorf("failed to get conn: %v", err)
}
// Get a client
client, err := conn.getClient()
if err != nil {
p.clearConn(conn)
p.releaseConn(conn)
// Try to redial, possible that the TCP session closed due to timeout
if retries == 0 {
retries++
goto START
}
return nil, nil, fmt.Errorf("failed to start stream: %v", err)
}
return conn, client, nil
}
// RPC is used to make an RPC call to a remote host
func (p *ConnPool) RPC(dc string, addr net.Addr, version int, method string, useTLS bool, args interface{}, reply interface{}) error {
p.once.Do(p.init)
// Get a usable client
conn, sc, err := p.getClient(dc, addr, version, useTLS)
if err != nil {
return fmt.Errorf("rpc error getting client: %v", err)
}
// Make the RPC call
err = msgpackrpc.CallWithCodec(sc.codec, method, args, reply)
if err != nil {
sc.Close()
// See the comment in leader_test.go TestLeader_ChangeServerID
// about how we found this. The tldr is that if we see this
// error, we know this connection is toast, so we should clear
// it and make a new one on the next attempt.
if lib.IsErrEOF(err) {
p.clearConn(conn)
}
p.releaseConn(conn)
return fmt.Errorf("rpc error making call: %v", err)
}
// Done with the connection
conn.returnClient(sc)
p.releaseConn(conn)
return nil
}
// Ping sends a Status.Ping message to the specified server and
// returns true if healthy, false if an error occurred
func (p *ConnPool) Ping(dc string, addr net.Addr, version int, useTLS bool) (bool, error) {
var out struct{}
err := p.RPC(dc, addr, version, "Status.Ping", useTLS, struct{}{}, &out)
return err == nil, err
}
// Reap is used to close conns open over maxTime
func (p *ConnPool) reap() {
for {
// Sleep for a while
select {
case <-p.shutdownCh:
return
case <-time.After(time.Second):
}
// Reap all old conns
p.Lock()
var removed []string
now := time.Now()
for host, conn := range p.pool {
// Skip recently used connections
if now.Sub(conn.lastUsed) < p.MaxTime {
continue
}
// Skip connections with active streams
if atomic.LoadInt32(&conn.refCount) > 0 {
continue
}
// Close the conn
conn.Close()
// Remove from pool
removed = append(removed, host)
}
for _, host := range removed {
delete(p.pool, host)
}
p.Unlock()
}
}