proxy.go

// Copyright (c) DataStax, Inc.
//
// 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 proxy

import (
	"bytes"
	"context"
	"crypto"
	"crypto/md5"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"math"
	"math/big"
	"net"
	"reflect"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/qzg/cql-proxy/parser"
	"github.com/qzg/cql-proxy/proxycore"

	"github.com/datastax/go-cassandra-native-protocol/datatype"
	"github.com/datastax/go-cassandra-native-protocol/frame"
	"github.com/datastax/go-cassandra-native-protocol/message"
	"github.com/datastax/go-cassandra-native-protocol/primitive"
	lru "github.com/hashicorp/golang-lru"
	"go.uber.org/zap"
)

var (
	encodedOneValue, _ = proxycore.EncodeType(datatype.Int, primitive.ProtocolVersion4, 1)
)

var ErrProxyClosed = errors.New("proxy closed")
var ErrProxyAlreadyConnected = errors.New("proxy already connected")
var ErrProxyNotConnected = errors.New("proxy not connected")

const preparedIdSize = 16

type PeerConfig struct {
	RPCAddr string   `yaml:"rpc-address"`
	DC      string   `yaml:"data-center,omitempty"`
	Tokens  []string `yaml:"tokens,omitempty"`
}

type Config struct {
	Version              primitive.ProtocolVersion
	MaxVersion           primitive.ProtocolVersion
	Auth                 proxycore.Authenticator
	Resolver             proxycore.EndpointResolver
	ReconnectPolicy      proxycore.ReconnectPolicy
	RetryPolicy          RetryPolicy
	IdempotentGraph      bool
	NumConns             int
	Logger               *zap.Logger
	HeartBeatInterval    time.Duration
	IdleTimeout          time.Duration
	RPCAddr              string
	DC                   string
	Tokens               []string
	Peers                []PeerConfig
	TrackUsage           bool
	UsageTrackSystem     bool
	UsageKeyspace        string
	UsageWruBytes        int
	UsageRruBytes        int
	UsageTable           string
	UsageFlushSeconds    int
	UsageHistogramsTable string
	// PreparedCache a cache that stores prepared queries. If not set it uses the default implementation with a max
	// capacity of ~100MB.
	PreparedCache proxycore.PreparedCache
}

type Proxy struct {
	ctx                 context.Context
	config              Config
	logger              *zap.Logger
	cluster             *proxycore.Cluster
	sessions            [primitive.ProtocolVersionDse2 + 1]sync.Map // Cache sessions per protocol version
	mu                  sync.Mutex
	isConnected         bool
	isClosing           bool
	clients             map[*client]struct{}
	listeners           map[*net.Listener]struct{}
	eventClients        sync.Map
	preparedCache       proxycore.PreparedCache
	preparedIdempotence sync.Map
	lb                  proxycore.LoadBalancer
	systemLocalValues   map[string]message.Column
	closed              chan struct{}
	localNode           *node
	nodes               []*node
	onceUsingGraphLog   sync.Once
	StatsManager        *statsManager
}

type node struct {
	addr   *net.IPAddr
	dc     string
	tokens []string
}

func (p *Proxy) OnEvent(event proxycore.Event) {
	switch evt := event.(type) {
	case *proxycore.SchemaChangeEvent:
		frm := frame.NewFrame(p.cluster.NegotiatedVersion, -1, evt.Message)
		p.eventClients.Range(func(key, _ interface{}) bool {
			cl := key.(*client)
			err := cl.conn.Write(proxycore.SenderFunc(func(writer io.Writer) error {
				return codec.EncodeFrame(frm, writer)
			}))
			cl.conn.LocalAddr()
			if err != nil {
				p.logger.Error("unable to send schema change event",
					zap.Stringer("client", cl.conn.RemoteAddr()),
					zap.Error(err))
				_ = cl.conn.Close()
			}
			return true
		})
	}
}

func NewProxy(ctx context.Context, config Config) *Proxy {
	if config.Version == 0 {
		config.Version = primitive.ProtocolVersion4
	}
	if config.MaxVersion == 0 {
		config.MaxVersion = primitive.ProtocolVersion4
	}
	if config.RetryPolicy == nil {
		config.RetryPolicy = NewDefaultRetryPolicy()
	}
	return &Proxy{
		ctx:       ctx,
		config:    config,
		logger:    proxycore.GetOrCreateNopLogger(config.Logger),
		clients:   make(map[*client]struct{}),
		listeners: make(map[*net.Listener]struct{}),
		closed:    make(chan struct{}),
	}
}

func (p *Proxy) Connect() error {
	p.mu.Lock()
	defer p.mu.Unlock()

	if p.isConnected {
		return ErrProxyAlreadyConnected
	}

	var err error
	p.preparedCache, err = getOrCreateDefaultPreparedCache(p.config.PreparedCache)
	if err != nil {
		return fmt.Errorf("unable to create prepared cache %w", err)
	}

	p.cluster, err = proxycore.ConnectCluster(p.ctx, proxycore.ClusterConfig{
		Version:           p.config.Version,
		Auth:              p.config.Auth,
		Resolver:          p.config.Resolver,
		ReconnectPolicy:   p.config.ReconnectPolicy,
		HeartBeatInterval: p.config.HeartBeatInterval,
		IdleTimeout:       p.config.IdleTimeout,
		Logger:            p.logger,
	})

	if err != nil {
		return fmt.Errorf("unable to connect to cluster %w", err)
	}

	err = p.cluster.Listen(p)
	if err != nil {
		return fmt.Errorf("unable to register to listen for schema events %w", err)
	}

	err = p.buildNodes()
	if err != nil {
		return fmt.Errorf("unable to build node information: %w", err)
	}

	p.buildLocalRow()

	p.lb = proxycore.NewRoundRobinLoadBalancer()
	err = p.cluster.Listen(p.lb)
	if err != nil {
		return err
	}

	sess, err := proxycore.ConnectSession(p.ctx, p.cluster, proxycore.SessionConfig{
		ReconnectPolicy:   p.config.ReconnectPolicy,
		NumConns:          p.config.NumConns,
		Version:           p.cluster.NegotiatedVersion,
		Auth:              p.config.Auth,
		HeartBeatInterval: p.config.HeartBeatInterval,
		IdleTimeout:       p.config.IdleTimeout,
		PreparedCache:     p.preparedCache,
		Logger:            p.logger,
	})

	if err != nil {
		return fmt.Errorf("unable to connect session %w", err)
	}

	p.sessions[p.cluster.NegotiatedVersion].Store("", sess) // No keyspace

	p.isConnected = true
	return nil
}

// Serve the proxy using the specified listener. It can be called multiple times with different listeners allowing
// them to share the same backend clusters.
func (p *Proxy) Serve(l net.Listener) (err error) {
	l = &closeOnceListener{Listener: l}
	defer l.Close()

	if err = p.addListener(&l); err != nil {
		return err
	}
	defer p.removeListener(&l)

	for {
		conn, err := l.Accept()
		if err != nil {
			select {
			case <-p.closed:
				return ErrProxyClosed
			default:
				return err
			}
		}
		p.handle(conn)
	}
}

func (p *Proxy) addListener(l *net.Listener) error {
	p.mu.Lock()
	defer p.mu.Unlock()
	if p.isClosing {
		return ErrProxyClosed
	}
	if !p.isConnected {
		return ErrProxyNotConnected
	}
	p.listeners[l] = struct{}{}
	return nil
}

func (p *Proxy) removeListener(l *net.Listener) {
	p.mu.Lock()
	defer p.mu.Unlock()
	delete(p.listeners, l)
}

func (p *Proxy) Close() error {
	p.mu.Lock()
	defer p.mu.Unlock()
	select {
	case <-p.closed:
	default:
		close(p.closed)
	}
	var err error
	for l := range p.listeners {
		if closeErr := (*l).Close(); closeErr != nil && err == nil {
			err = closeErr
		}
	}
	for cl := range p.clients {
		_ = cl.conn.Close()
		p.eventClients.Delete(cl)
		delete(p.clients, cl)
	}
	return err
}

func (p *Proxy) Ready() bool {
	return true
}

func (p *Proxy) OutageDuration() time.Duration {
	return p.cluster.OutageDuration()
}

func (p *Proxy) handle(conn net.Conn) {
	if tcpConn, ok := conn.(*net.TCPConn); ok {
		if err := tcpConn.SetKeepAlive(false); err != nil {
			p.logger.Warn("failed to disable keepalive on connection", zap.Error(err))
		}
		if err := tcpConn.SetNoDelay(true); err != nil {
			p.logger.Warn("failed to set TCP_NODELAY on connection", zap.Error(err))
		}
	}

	cl := &client{
		ctx:                 p.ctx,
		proxy:               p,
		preparedSystemQuery: make(map[[preparedIdSize]byte]interface{}),
	}
	p.addClient(cl)
	cl.conn = proxycore.NewConn(conn, cl)
	cl.conn.Start()
}

func (p *Proxy) maybeCreateSession(version primitive.ProtocolVersion, keyspace string) (*proxycore.Session, error) {
	p.mu.Lock()
	defer p.mu.Unlock()
	if cachedSession, ok := p.sessions[version].Load(keyspace); ok {
		return cachedSession.(*proxycore.Session), nil
	} else {
		sess, err := proxycore.ConnectSession(p.ctx, p.cluster, proxycore.SessionConfig{
			ReconnectPolicy:   p.config.ReconnectPolicy,
			NumConns:          p.config.NumConns,
			Version:           version,
			Auth:              p.config.Auth,
			PreparedCache:     p.preparedCache,
			Keyspace:          keyspace,
			HeartBeatInterval: p.config.HeartBeatInterval,
			IdleTimeout:       p.config.IdleTimeout,
			Logger:            p.logger,
		})
		if err != nil {
			return nil, err
		}
		p.sessions[version].Store(keyspace, sess)
		return sess, nil
	}
}

func (p *Proxy) findSession(version primitive.ProtocolVersion, keyspace string) (*proxycore.Session, error) {
	if s, ok := p.sessions[version].Load(keyspace); ok {
		return s.(*proxycore.Session), nil
	} else {
		return p.maybeCreateSession(version, keyspace)
	}
}

func (p *Proxy) newQueryPlan() proxycore.QueryPlan {
	return p.lb.NewQueryPlan()
}

var (
	schemaVersion, _ = primitive.ParseUuid("4f2b29e6-59b5-4e2d-8fd6-01e32e67f0d7")
)

func (p *Proxy) buildNodes() (err error) {
	numPeers := len(p.config.Peers)
	nodes := make([]*node, 0, numPeers+1)

	var localAddr *net.IPAddr
	if len(p.config.RPCAddr) > 0 {
		localAddr, err = net.ResolveIPAddr("ip", p.config.RPCAddr)
		if err != nil {
			return fmt.Errorf("invalid RPC address: %w", err)
		}
	} else if numPeers > 0 {
		return errors.New("peers provided, but RPC address is not set")
	}

	localDC := p.config.DC
	if len(localDC) == 0 {
		localDC = p.cluster.Info.LocalDC
		p.logger.Info("no local DC configured using DC from the first successful contact point",
			zap.String("dc", localDC))
	}

	var localTokens []string
	calculateTokens := false
	if len(p.config.Tokens) > 0 {
		localTokens = p.config.Tokens
	} else {
		calculateTokens = true
		localTokens = []string{strconv.FormatInt(math.MinInt64, 10)}
	}

	p.localNode = &node{
		addr:   localAddr,
		dc:     localDC,
		tokens: localTokens,
	}
	nodes = append(nodes, p.localNode)

	for i, peer := range p.config.Peers {
		if len(peer.RPCAddr) == 0 {
			return fmt.Errorf("no 'rpc-address' provided for peer #%d", i+1)
		}
		addr, err := net.ResolveIPAddr("ip", peer.RPCAddr)
		if err != nil {
			return fmt.Errorf("invalid peer address: %w", err)
		}
		if compareIPAddr(localAddr, addr) == 0 {
			p.logger.Info("ignoring local address in peers configuration", zap.Stringer("localAddr", localAddr))
			continue
		}
		dc := peer.DC
		if len(dc) == 0 {
			dc = localDC
		}
		if !calculateTokens && len(peer.Tokens) == 0 {
			return errors.New("tokens must be provided for all peer proxies if tokens are provided for this proxy")
		}
		nodes = append(nodes, &node{
			addr:   addr,
			dc:     dc,
			tokens: peer.Tokens,
		})
	}

	// If tokens are not provided then we calculate tokens by sorting the addresses and assigning an even portion of the
	// ring to each proxy. This should be deterministic in multiple independent proxies, assuming they have the same
	// list of peers.
	if calculateTokens && len(nodes) > 1 {
		sort.Slice(nodes, func(i, j int) bool {
			return compareIPAddr(nodes[i].addr, nodes[j].addr) < 0
		})

		var numTokens big.Int
		numTokens.SetUint64(math.MaxUint64/uint64(numPeers+1) + 1)
		start := big.NewInt(math.MinInt64)

		for _, n := range nodes {
			n.tokens = []string{start.Text(10)}
			start.Add(start, &numTokens)
		}
	}

	p.nodes = nodes

	return nil
}

func (p *Proxy) buildLocalRow() {
	p.systemLocalValues = map[string]message.Column{
		"key":                     p.encodeTypeFatal(datatype.Varchar, "local"),
		"data_center":             p.encodeTypeFatal(datatype.Varchar, p.localNode.dc),
		"rack":                    p.encodeTypeFatal(datatype.Varchar, "rack1"),
		"tokens":                  p.encodeTypeFatal(datatype.NewListType(datatype.Varchar), p.localNode.tokens),
		"release_version":         p.encodeTypeFatal(datatype.Varchar, p.cluster.Info.ReleaseVersion),
		"partitioner":             p.encodeTypeFatal(datatype.Varchar, p.cluster.Info.Partitioner),
		"cluster_name":            p.encodeTypeFatal(datatype.Varchar, "cql-proxy"),
		"cql_version":             p.encodeTypeFatal(datatype.Varchar, p.cluster.Info.CQLVersion),
		"schema_version":          p.encodeTypeFatal(datatype.Uuid, schemaVersion), // TODO: Make this match the downstream cluster(s)
		"native_protocol_version": p.encodeTypeFatal(datatype.Varchar, p.cluster.NegotiatedVersion.String()),
		"dse_version":             p.encodeTypeFatal(datatype.Varchar, p.cluster.Info.DSEVersion),
	}
}

func (p *Proxy) encodeTypeFatal(dt datatype.DataType, val interface{}) []byte {
	encoded, err := proxycore.EncodeType(dt, p.cluster.NegotiatedVersion, val)
	if err != nil {
		p.logger.Fatal("unable to encode type", zap.Error(err))
	}
	return encoded
}

// isIdempotent checks whether a prepared ID is idempotent.
// If the proxy receives a query that it's never prepared then this will also return false.
func (p *Proxy) isIdempotent(id []byte) bool {
	if val, ok := p.preparedIdempotence.Load(preparedIdKey(id)); !ok {
		// This should only happen if the proxy has never had a "PREPARE" request for this query ID.
		p.logger.Error("unable to determine if prepared statement is idempotent",
			zap.String("preparedID", hex.EncodeToString(id)))
		return false
	} else {
		return val.(bool)
	}
}

// maybeStorePreparedIdempotence stores the idempotence of a "PREPARE" request's query.
// This information is used by future "EXECUTE" requests when they need to be retried.
func (p *Proxy) maybeStorePreparedIdempotence(raw *frame.RawFrame, msg message.Message) {
	if prepareMsg, ok := msg.(*message.Prepare); ok && raw.Header.OpCode == primitive.OpCodeResult { // Prepared result
		frm, err := codec.ConvertFromRawFrame(raw)
		if err != nil {
			p.logger.Error("error attempting to decode prepared result message")
		} else if _, ok = frm.Body.Message.(*message.PreparedResult); !ok { // TODO: Use prepared type data to disambiguate idempotency
			p.logger.Error("expected prepared result message, but got something else")
		} else {
			idempotent, err := parser.IsQueryIdempotent(prepareMsg.Query)
			if err != nil {
				p.logger.Error("error parsing query for idempotence", zap.Error(err))
			} else if result, ok := frm.Body.Message.(*message.PreparedResult); ok {
				p.preparedIdempotence.Store(preparedIdKey(result.PreparedQueryId), idempotent)
			} else {
				p.logger.Error("expected prepared result, but got some other type of message",
					zap.Stringer("type", reflect.TypeOf(frm.Body.Message)))
			}
		}
	}
}

func (p *Proxy) maybeLogUsingGraph() {
	p.onceUsingGraphLog.Do(func() {
		p.logger.Warn("graph queries default to *not* being considered idempotent and will not be retried automatically. Use the idempotent graph flag to override.")
	})
}

func (p *Proxy) addClient(cl *client) {
	p.mu.Lock()
	defer p.mu.Unlock()
	p.clients[cl] = struct{}{}
}

func (p *Proxy) registerForEvents(cl *client) {
	p.eventClients.Store(cl, struct{}{})
}

func (p *Proxy) removeClient(cl *client) {
	p.eventClients.Delete(cl)

	p.mu.Lock()
	defer p.mu.Unlock()
	delete(p.clients, cl)

}

type client struct {
	ctx                 context.Context
	proxy               *Proxy
	conn                *proxycore.Conn
	keyspace            string
	preparedSystemQuery map[[16]byte]interface{}
}

func (c *client) Receive(reader io.Reader) error {
	raw, err := codec.DecodeRawFrame(reader)
	if err != nil {
		if !errors.Is(err, io.EOF) {
			c.proxy.logger.Error("unable to decode frame", zap.Error(err))
		}
		return err
	}

	if raw.Header.Version > c.proxy.config.MaxVersion || raw.Header.Version < primitive.ProtocolVersion3 {
		c.send(raw.Header, &message.ProtocolError{
			ErrorMessage: fmt.Sprintf("Invalid or unsupported protocol version %d", raw.Header.Version),
		})
		return nil
	}

	body, err := codec.DecodeBody(raw.Header, bytes.NewReader(raw.Body))
	if err != nil {
		c.proxy.logger.Error("unable to decode body", zap.Error(err))
		return err
	}

	switch msg := body.Message.(type) {
	case *message.Options:
		c.send(raw.Header, &message.Supported{Options: map[string][]string{
			"CQL_VERSION": {c.proxy.cluster.Info.CQLVersion},
			"COMPRESSION": {},
		}})
	case *message.Startup:
		c.send(raw.Header, &message.Ready{})
	case *message.Register:
		for _, t := range msg.EventTypes {
			if t == primitive.EventTypeSchemaChange {
				c.proxy.registerForEvents(c)
			}
		}
		c.send(raw.Header, &message.Ready{})
	case *message.Prepare:
		c.handlePrepare(raw, msg)
	case *partialExecute:
		c.handleExecute(raw, msg, body.CustomPayload)
	case *partialQuery:
		c.handleQuery(raw, msg, body.CustomPayload)
	case *partialBatch:
		c.execute(raw, notDetermined, c.keyspace, msg)
	default:
		c.send(raw.Header, &message.ProtocolError{ErrorMessage: "Unsupported operation"})
	}

	return nil
}

func (c *client) execute(raw *frame.RawFrame, state idempotentState, keyspace string, msg message.Message) {
	if sess, err := c.proxy.findSession(raw.Header.Version, c.keyspace); err == nil {
		req := &request{
			client:  c,
			session: sess,
			state:   state,
			msg:     msg,
			//stmt:     stmt,
			keyspace: keyspace,
			done:     false,
			stream:   raw.Header.StreamId,
			qp:       c.proxy.newQueryPlan(),
			raw:      raw,
		}
		req.Execute(true)
	} else {
		c.send(raw.Header, &message.ServerError{ErrorMessage: "Attempted to use invalid keyspace"})
	}
}

func (c *client) handlePrepare(raw *frame.RawFrame, msg *message.Prepare) {
	c.proxy.logger.Debug("handling prepare", zap.String("query", msg.Query), zap.Int16("stream", raw.Header.StreamId))

	keyspace := c.keyspace
	if len(msg.Keyspace) != 0 {
		keyspace = msg.Keyspace
	}
	handled, stmt, err := parser.IsQueryHandled(parser.IdentifierFromString(keyspace), msg.Query)

	if handled {
		hdr := raw.Header

		if err != nil {
			c.proxy.logger.Error("error parsing query to see if it's handled", zap.Error(err))
			c.send(hdr, &message.Invalid{ErrorMessage: err.Error()})
		} else {
			switch s := stmt.(type) {
			case *parser.SelectStatement:
				if systemColumns, ok := parser.SystemColumnsByName[s.Table]; ok {
					if columns, err := parser.FilterColumns(s, systemColumns); err != nil {
						c.send(hdr, &message.Invalid{ErrorMessage: err.Error()})
					} else {
						id := md5.Sum([]byte(msg.Query + keyspace))
						c.send(hdr, &message.PreparedResult{
							PreparedQueryId: id[:],
							ResultMetadata: &message.RowsMetadata{
								ColumnCount: int32(len(columns)),
								Columns:     columns,
							},
						})
						c.preparedSystemQuery[id] = stmt
					}
				} else {
					c.send(hdr, &message.Invalid{ErrorMessage: "Doesn't exist"})
				}
			case *parser.UseStatement:
				id := md5.Sum([]byte(msg.Query))
				c.preparedSystemQuery[id] = stmt
				c.send(hdr, &message.PreparedResult{
					PreparedQueryId: id[:],
				})
			default:
				c.send(hdr, &message.ServerError{ErrorMessage: "Proxy attempted to intercept an unhandled query"})
			}
		}

	} else {
		c.execute(raw, isIdempotent, keyspace, msg) // Prepared statements can be retried themselves
	}
}

func (c *client) handleExecute(raw *frame.RawFrame, msg *partialExecute, customPayload map[string][]byte) {
	id := preparedIdKey(msg.queryId)
	if stmt, ok := c.preparedSystemQuery[id]; ok {
		c.interceptSystemQuery(raw.Header, stmt)
	} else {
		c.execute(raw, c.getDefaultIdempotency(customPayload), "", msg)
	}
}

func (c *client) handleQuery(raw *frame.RawFrame, msg *partialQuery, customPayload map[string][]byte) {
	c.proxy.logger.Debug("handling query", zap.String("query", msg.query), zap.Int16("stream", raw.Header.StreamId))
	//c.proxy.logger.Info("handling query", zap.String("query", msg.query), zap.Int16("stream", raw.Header.StreamId))
	//c.proxy.logger.Info("Query/Statement Size:", zap.Int32("message size in bytes", raw.Header.BodyLength))
	handled, stmt, err := parser.IsQueryHandled(parser.IdentifierFromString(c.keyspace), msg.query)

	// if raw.Body[3] == 0xc {
	// 	raw.Body = []uint8{0, 0, 0, 19, 115, 101, 108, 101, 99, 116, 32, 42, 32, 102, 114, 111, 109, 32, 116, 98, 108, 49, 59, 0, 1, 52, 0, 0, 0, 100, 0, 8, 0, 5, 243, 97, 47, 75, 4, 192}
	// }

	if handled {
		if err != nil {
			c.proxy.logger.Error("error parsing query to see if it's handled", zap.Error(err))
			c.send(raw.Header, &message.Invalid{ErrorMessage: err.Error()})
		} else {
			c.interceptSystemQuery(raw.Header, stmt)
		}
	} else {
		c.execute(raw, c.getDefaultIdempotency(customPayload), c.keyspace, msg)
	}
}

func (c *client) getDefaultIdempotency(customPayload map[string][]byte) idempotentState {
	state := notDetermined
	if _, ok := customPayload["graph-source"]; ok { // Graph queries default to non-idempotent unless overridden
		c.proxy.maybeLogUsingGraph()
		if c.proxy.config.IdempotentGraph {
			state = isIdempotent
		} else {
			state = notIdempotent
		}
	}
	return state
}

func (c *client) filterSystemLocalValues(stmt *parser.SelectStatement, filtered []*message.ColumnMetadata) (row []message.Column, err error) {
	return parser.FilterValues(stmt, filtered, func(name string) (value message.Column, err error) {
		if name == "rpc_address" {
			return proxycore.EncodeType(datatype.Inet, c.proxy.cluster.NegotiatedVersion, c.localIP())
		} else if name == "host_id" {
			return proxycore.EncodeType(datatype.Uuid, c.proxy.cluster.NegotiatedVersion, nameBasedUUID(c.localIP().String()))
		} else if val, ok := c.proxy.systemLocalValues[name]; ok {
			return val, nil
		} else if name == parser.CountValueName {
			return encodedOneValue, nil
		} else {
			return nil, fmt.Errorf("no column value for %s", name)
		}
	})
}

func (c *client) localIP() net.IP {
	if c.proxy.localNode.addr != nil {
		return c.proxy.localNode.addr.IP
	} else {
		switch a := c.conn.LocalAddr().(type) {
		case *net.TCPAddr:
			return a.IP
		case *net.IPAddr:
			return a.IP
		default:
			panic("unhandled local address type")
		}
	}
}

func (c *client) filterSystemPeerValues(stmt *parser.SelectStatement, filtered []*message.ColumnMetadata, peer *node, peerCount int) (row []message.Column, err error) {
	return parser.FilterValues(stmt, filtered, func(name string) (value message.Column, err error) {
		if name == "data_center" {
			return proxycore.EncodeType(datatype.Varchar, c.proxy.cluster.NegotiatedVersion, peer.dc)
		} else if name == "host_id" {
			return proxycore.EncodeType(datatype.Uuid, c.proxy.cluster.NegotiatedVersion, nameBasedUUID(peer.addr.String()))
		} else if name == "tokens" {
			return proxycore.EncodeType(datatype.NewListType(datatype.Varchar), c.proxy.cluster.NegotiatedVersion, peer.tokens)
		} else if name == "peer" {
			return proxycore.EncodeType(datatype.Inet, c.proxy.cluster.NegotiatedVersion, peer.addr.IP)
		} else if name == "rpc_address" {
			return proxycore.EncodeType(datatype.Inet, c.proxy.cluster.NegotiatedVersion, peer.addr.IP)
		} else if val, ok := c.proxy.systemLocalValues[name]; ok {
			return val, nil
		} else if name == parser.CountValueName {
			return proxycore.EncodeType(datatype.Int, c.proxy.cluster.NegotiatedVersion, peerCount)
		} else {
			return nil, fmt.Errorf("no column value for %s", name)
		}
	})
}

func (c *client) interceptSystemQuery(hdr *frame.Header, stmt interface{}) {
	switch s := stmt.(type) {
	case *parser.SelectStatement:
		if s.Table == "local" {
			localColumns := parser.SystemLocalColumns
			if len(c.proxy.cluster.Info.DSEVersion) > 0 {
				localColumns = parser.DseSystemLocalColumns
			}
			if columns, err := parser.FilterColumns(s, localColumns); err != nil {
				c.send(hdr, &message.Invalid{ErrorMessage: err.Error()})
			} else if row, err := c.filterSystemLocalValues(s, columns); err != nil {
				c.send(hdr, &message.Invalid{ErrorMessage: err.Error()})
			} else {
				c.send(hdr, &message.RowsResult{
					Metadata: &message.RowsMetadata{
						ColumnCount: int32(len(columns)),
						Columns:     columns,
					},
					Data: []message.Row{row},
				})
			}
		} else if s.Table == "peers" {
			peersColumns := parser.SystemPeersColumns
			if len(c.proxy.cluster.Info.DSEVersion) > 0 {
				peersColumns = parser.DseSystemPeersColumns
			}
			if columns, err := parser.FilterColumns(s, peersColumns); err != nil {
				c.send(hdr, &message.Invalid{ErrorMessage: err.Error()})
			} else {
				var data []message.Row
				for _, n := range c.proxy.nodes {
					if n != c.proxy.localNode {
						var row message.Row
						row, err = c.filterSystemPeerValues(s, columns, n, len(c.proxy.nodes)-1)
						if err != nil {
							break
						}
						data = append(data, row)
					}
				}
				if err != nil {
					c.send(hdr, &message.Invalid{ErrorMessage: err.Error()})
				} else {
					c.send(hdr, &message.RowsResult{
						Metadata: &message.RowsMetadata{
							ColumnCount: int32(len(columns)),
							Columns:     columns,
						},
						Data: data,
					})
				}
			}
		} else if columns, ok := parser.SystemColumnsByName[s.Table]; ok {
			c.send(hdr, &message.RowsResult{
				Metadata: &message.RowsMetadata{
					ColumnCount: int32(len(columns)),
					Columns:     columns,
				},
			})
		} else {
			c.send(hdr, &message.Invalid{ErrorMessage: "Doesn't exist"})
		}
	case *parser.UseStatement:
		if _, err := c.proxy.maybeCreateSession(hdr.Version, s.Keyspace); err != nil {
			c.send(hdr, &message.ServerError{ErrorMessage: "Proxy unable to create new session for keyspace"})
		} else {
			c.keyspace = s.Keyspace
			c.send(hdr, &message.SetKeyspaceResult{Keyspace: s.Keyspace})
		}
	default:
		c.send(hdr, &message.ServerError{ErrorMessage: "Proxy attempted to intercept an unhandled query"})
	}
}

func (c *client) send(hdr *frame.Header, msg message.Message) {
	_ = c.conn.Write(proxycore.SenderFunc(func(writer io.Writer) error {
		return codec.EncodeFrame(frame.NewFrame(hdr.Version, hdr.StreamId, msg), writer)
	}))
}

func (c *client) Closing(_ error) {
	c.proxy.removeClient(c)
}

func getOrCreateDefaultPreparedCache(cache proxycore.PreparedCache) (proxycore.PreparedCache, error) {
	if cache == nil {
		return NewDefaultPreparedCache(1e8 / 256) // ~100MB with an average query size of 256 bytes
	}
	return cache, nil
}

// NewDefaultPreparedCache creates a new default prepared cache capping the max item capacity to `size`.
func NewDefaultPreparedCache(size int) (proxycore.PreparedCache, error) {
	cache, err := lru.New(size)
	if err != nil {
		return nil, err
	}
	return &defaultPreparedCache{cache}, nil
}

type defaultPreparedCache struct {
	cache *lru.Cache
}

func (d defaultPreparedCache) Store(id string, entry *proxycore.PreparedEntry) {
	d.cache.Add(id, entry)
}

func (d defaultPreparedCache) Load(id string) (entry *proxycore.PreparedEntry, ok bool) {
	if val, ok := d.cache.Get(id); ok {
		return val.(*proxycore.PreparedEntry), true
	}
	return nil, false
}

func preparedIdKey(bytes []byte) [preparedIdSize]byte {
	var buf [preparedIdSize]byte
	copy(buf[:], bytes)
	return buf
}

func nameBasedUUID(name string) primitive.UUID {
	var uuid primitive.UUID
	m := crypto.MD5.New()
	_, _ = io.WriteString(m, name)
	hash := m.Sum(nil)
	for i := 0; i < len(uuid); i++ {
		uuid[i] = hash[i]
	}
	uuid[6] &= 0x0F
	uuid[6] |= 0x30
	uuid[8] &= 0x3F
	uuid[8] |= 0x80
	return uuid
}

func compareIPAddr(a *net.IPAddr, b *net.IPAddr) int {
	if a == b {
		return 0
	}

	res := bytes.Compare(a.IP, b.IP)
	if res != 0 {
		return res
	}

	res = strings.Compare(a.Zone, b.Zone)
	if res != 0 {
		return res
	}

	return 0
}

// Wrap the listener so that if it's closed in the serve loop it doesn't race with proxy Close()
type closeOnceListener struct {
	net.Listener
	once     sync.Once
	closeErr error
}

func (oc *closeOnceListener) Close() error {
	oc.once.Do(oc.close)
	return oc.closeErr
}

func (oc *closeOnceListener) close() { oc.closeErr = oc.Listener.Close() }