connectionpool.go

// Copyright (c) 2012 The gocql Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gocql

import (
	"fmt"
	"math/rand"
	"net"
	"sync"
	"time"

	"github.com/gocql/gocql/debounce"
)

// interface to implement to receive the host information
type SetHosts interface {
	SetHosts(hosts []*HostInfo)
}

// interface to implement to receive the partitioner value
type SetPartitioner interface {
	SetPartitioner(partitioner string)
}

// interface to implement to receive the tablets value
// Experimental, this interface and use may change
type SetTablets interface {
	SetTablets(tablets []*TabletInfo)
}

type policyConnPool struct {
	session *Session

	port     int
	numConns int
	keyspace string

	mu            sync.RWMutex
	hostConnPools map[string]*hostConnPool
}

func connConfig(cfg *ClusterConfig) (*ConnConfig, error) {
	hostDialer := cfg.HostDialer

	if hostDialer == nil {
		dialer := cfg.Dialer
		if dialer == nil {
			d := net.Dialer{
				Timeout: cfg.ConnectTimeout,
			}
			if cfg.SocketKeepalive > 0 {
				d.KeepAlive = cfg.SocketKeepalive
			}
			dialer = &ScyllaShardAwareDialer{d}
		}

		hostDialer = &scyllaDialer{
			dialer:    dialer,
			logger:    cfg.logger(),
			tlsConfig: cfg.getActualTLSConfig(),
			cfg:       cfg,
		}
	}

	return &ConnConfig{
		ProtoVersion:   cfg.ProtoVersion,
		CQLVersion:     cfg.CQLVersion,
		Timeout:        cfg.Timeout,
		WriteTimeout:   cfg.WriteTimeout,
		ConnectTimeout: cfg.ConnectTimeout,
		Dialer:         cfg.Dialer,
		HostDialer:     hostDialer,
		Compressor:     cfg.Compressor,
		Authenticator:  cfg.Authenticator,
		AuthProvider:   cfg.AuthProvider,
		Keepalive:      cfg.SocketKeepalive,
		Logger:         cfg.logger(),
		tlsConfig:      cfg.getActualTLSConfig(),
	}, nil
}

func newPolicyConnPool(session *Session) *policyConnPool {
	// create the pool
	pool := &policyConnPool{
		session:       session,
		port:          session.cfg.Port,
		numConns:      session.cfg.NumConns,
		keyspace:      session.cfg.Keyspace,
		hostConnPools: map[string]*hostConnPool{},
	}

	return pool
}

func (p *policyConnPool) SetHosts(hosts []*HostInfo) {
	p.mu.Lock()
	defer p.mu.Unlock()

	toRemove := make(map[string]struct{})
	for hostID := range p.hostConnPools {
		toRemove[hostID] = struct{}{}
	}

	pools := make(chan *hostConnPool)
	createCount := 0
	for _, host := range hosts {
		if !host.IsUp() {
			// don't create a connection pool for a down host
			continue
		}
		hostID := host.HostID()
		if _, exists := p.hostConnPools[hostID]; exists {
			// still have this host, so don't remove it
			delete(toRemove, hostID)
			continue
		}

		createCount++
		go func(host *HostInfo) {
			// create a connection pool for the host
			pools <- newHostConnPool(
				p.session,
				host,
				p.port,
				p.numConns,
				p.keyspace,
			)
		}(host)
	}

	// add created pools
	for createCount > 0 {
		pool := <-pools
		createCount--
		if pool.Size() > 0 {
			// add pool only if there a connections available
			p.hostConnPools[pool.host.HostID()] = pool
		}
	}

	for addr := range toRemove {
		pool := p.hostConnPools[addr]
		delete(p.hostConnPools, addr)
		go pool.Close()
	}
}

func (p *policyConnPool) InFlight() int {
	p.mu.RLock()
	count := 0
	for _, pool := range p.hostConnPools {
		count += pool.InFlight()
	}
	p.mu.RUnlock()

	return count
}

func (p *policyConnPool) Size() int {
	p.mu.RLock()
	count := 0
	for _, pool := range p.hostConnPools {
		count += pool.Size()
	}
	p.mu.RUnlock()

	return count
}

func (p *policyConnPool) getPool(host *HostInfo) (pool *hostConnPool, ok bool) {
	hostID := host.HostID()
	p.mu.RLock()
	pool, ok = p.hostConnPools[hostID]
	p.mu.RUnlock()
	return
}

func (p *policyConnPool) Close() {
	p.mu.Lock()
	defer p.mu.Unlock()

	// close the pools
	for addr, pool := range p.hostConnPools {
		delete(p.hostConnPools, addr)
		pool.Close()
	}
}

func (p *policyConnPool) addHost(host *HostInfo) {
	hostID := host.HostID()
	p.mu.Lock()
	pool, ok := p.hostConnPools[hostID]
	if !ok {
		pool = newHostConnPool(
			p.session,
			host,
			host.Port(), // TODO: if port == 0 use pool.port?
			p.numConns,
			p.keyspace,
		)

		p.hostConnPools[hostID] = pool
	}
	p.mu.Unlock()

	pool.fill_debounce()
}

func (p *policyConnPool) removeHost(hostID string) {
	p.mu.Lock()
	pool, ok := p.hostConnPools[hostID]
	if !ok {
		p.mu.Unlock()
		return
	}

	delete(p.hostConnPools, hostID)
	p.mu.Unlock()

	go pool.Close()
}

// hostConnPool is a connection pool for a single host.
// Connection selection is based on a provided ConnSelectionPolicy
type hostConnPool struct {
	session  *Session
	host     *HostInfo
	size     int
	keyspace string
	// protection for connPicker, closed, filling
	mu         sync.RWMutex
	connPicker ConnPicker
	closed     bool
	filling    bool
	debouncer  *debounce.SimpleDebouncer

	logger StdLogger
}

func (h *hostConnPool) String() string {
	h.mu.RLock()
	defer h.mu.RUnlock()
	size, _ := h.connPicker.Size()
	return fmt.Sprintf("[filling=%v closed=%v conns=%v size=%v host=%v]",
		h.filling, h.closed, size, h.size, h.host)
}

func newHostConnPool(session *Session, host *HostInfo, port, size int,
	keyspace string) *hostConnPool {

	pool := &hostConnPool{
		session:    session,
		host:       host,
		size:       size,
		keyspace:   keyspace,
		connPicker: nopConnPicker{},
		filling:    false,
		closed:     false,
		logger:     session.logger,
		debouncer:  debounce.NewSimpleDebouncer(),
	}

	// the pool is not filled or connected
	return pool
}

// Pick a connection from this connection pool for the given query.
func (pool *hostConnPool) Pick(token Token, qry ExecutableQuery) *Conn {
	pool.mu.RLock()
	defer pool.mu.RUnlock()

	if pool.closed {
		return nil
	}

	size, missing := pool.connPicker.Size()
	if missing > 0 {
		// try to fill the pool
		go pool.fill_debounce()

		if size == 0 {
			return nil
		}
	}

	return pool.connPicker.Pick(token, qry)
}

// Size returns the number of connections currently active in the pool
func (pool *hostConnPool) Size() int {
	pool.mu.RLock()
	defer pool.mu.RUnlock()

	size, _ := pool.connPicker.Size()
	return size
}

// Size returns the number of connections currently active in the pool
func (pool *hostConnPool) InFlight() int {
	pool.mu.RLock()
	defer pool.mu.RUnlock()

	size := pool.connPicker.InFlight()
	return size
}

// Close the connection pool
func (pool *hostConnPool) Close() {
	pool.mu.Lock()
	defer pool.mu.Unlock()

	if !pool.closed {
		pool.connPicker.Close()
	}
	pool.closed = true
}

// Fill the connection pool
func (pool *hostConnPool) fill() {
	pool.mu.RLock()
	// avoid filling a closed pool, or concurrent filling
	if pool.closed || pool.filling {
		pool.mu.RUnlock()
		return
	}

	// determine the filling work to be done
	startCount, fillCount := pool.connPicker.Size()

	// avoid filling a full (or overfull) pool
	if fillCount <= 0 {
		pool.mu.RUnlock()
		return
	}

	// switch from read to write lock
	pool.mu.RUnlock()
	pool.mu.Lock()

	startCount, fillCount = pool.connPicker.Size()
	if pool.closed || pool.filling || fillCount <= 0 {
		// looks like another goroutine already beat this
		// goroutine to the filling
		pool.mu.Unlock()
		return
	}

	// ok fill the pool
	pool.filling = true

	// allow others to access the pool while filling
	pool.mu.Unlock()
	// only this goroutine should make calls to fill/empty the pool at this
	// point until after this routine or its subordinates calls
	// fillingStopped

	// fill only the first connection synchronously
	if startCount == 0 {
		err := pool.connect()
		pool.logConnectErr(err)

		if err != nil {
			// probably unreachable host
			pool.fillingStopped(err)
			return
		}
		// notify the session that this node is connected
		go pool.session.handleNodeConnected(pool.host)

		// filled one, let's reload it to see if it has changed
		pool.mu.RLock()
		_, fillCount = pool.connPicker.Size()
		pool.mu.RUnlock()
	}

	// fill the rest of the pool asynchronously
	go func() {
		err := pool.connectMany(fillCount)

		// mark the end of filling
		pool.fillingStopped(err)

		if err == nil && startCount > 0 {
			// notify the session that this node is connected again
			go pool.session.handleNodeConnected(pool.host)
		}
	}()
}

func (pool *hostConnPool) fill_debounce() {
	pool.debouncer.Debounce(pool.fill)
}

func (pool *hostConnPool) logConnectErr(err error) {
	if opErr, ok := err.(*net.OpError); ok && (opErr.Op == "dial" || opErr.Op == "read") {
		// connection refused
		// these are typical during a node outage so avoid log spam.
		if gocqlDebug {
			pool.logger.Printf("unable to dial %q: %v\n", pool.host, err)
		}
	} else if err != nil {
		// unexpected error
		pool.logger.Printf("error: failed to connect to %q due to error: %v", pool.host, err)
	}
}

// transition back to a not-filling state.
func (pool *hostConnPool) fillingStopped(err error) {
	if err != nil {
		if gocqlDebug {
			pool.logger.Printf("gocql: filling stopped %q: %v\n", pool.host.ConnectAddress(), err)
		}
		// wait for some time to avoid back-to-back filling
		// this provides some time between failed attempts
		// to fill the pool for the host to recover
		time.Sleep(time.Duration(rand.Int31n(100)+31) * time.Millisecond)
	}

	pool.mu.Lock()
	pool.filling = false
	count, _ := pool.connPicker.Size()
	host := pool.host
	port := pool.host.Port()
	pool.mu.Unlock()

	// if we errored and the size is now zero, make sure the host is marked as down
	// see https://github.com/gocql/gocql/issues/1614
	if gocqlDebug {
		pool.logger.Printf("gocql: conns of pool after stopped %q: %v\n", host.ConnectAddress(), count)
	}
	if err != nil && count == 0 {
		if pool.session.cfg.ConvictionPolicy.AddFailure(err, host) {
			pool.session.handleNodeDown(host.ConnectAddress(), port)
		}
	}
}

// connectMany creates new connections concurrent.
func (pool *hostConnPool) connectMany(count int) error {
	if count == 0 {
		return nil
	}
	var (
		wg         sync.WaitGroup
		mu         sync.Mutex
		connectErr error
	)
	wg.Add(count)
	for i := 0; i < count; i++ {
		go func() {
			defer wg.Done()
			err := pool.connect()
			pool.logConnectErr(err)
			if err != nil {
				mu.Lock()
				connectErr = err
				mu.Unlock()
			}
		}()
	}
	// wait for all connections are done
	wg.Wait()

	return connectErr
}

// create a new connection to the host and add it to the pool
func (pool *hostConnPool) connect() (err error) {
	pool.mu.Lock()
	shardID, nrShards := pool.connPicker.NextShard()
	pool.mu.Unlock()

	// TODO: provide a more robust connection retry mechanism, we should also
	// be able to detect hosts that come up by trying to connect to downed ones.
	// try to connect
	var conn *Conn
	reconnectionPolicy := pool.session.cfg.ReconnectionPolicy
	for i := 0; i < reconnectionPolicy.GetMaxRetries(); i++ {
		conn, err = pool.session.connectShard(pool.session.ctx, pool.host, pool, shardID, nrShards)
		if err == nil {
			break
		}
		if opErr, isOpErr := err.(*net.OpError); isOpErr {
			// if the error is not a temporary error (ex: network unreachable) don't
			//  retry
			if !opErr.Temporary() {
				break
			}
		}
		if gocqlDebug {
			pool.logger.Printf("gocql: connection failed %q: %v, reconnecting with %T\n",
				pool.host.ConnectAddress(), err, reconnectionPolicy)
		}
		time.Sleep(reconnectionPolicy.GetInterval(i))
	}

	if err != nil {
		return err
	}

	if pool.keyspace != "" {
		// set the keyspace
		if err = conn.UseKeyspace(pool.keyspace); err != nil {
			conn.Close()
			return err
		}
	}

	// add the Conn to the pool
	pool.mu.Lock()
	defer pool.mu.Unlock()

	if pool.closed {
		conn.Close()
		return nil
	}

	// lazily initialize the connPicker when we know the required type
	pool.initConnPicker(conn)
	pool.connPicker.Put(conn)

	return nil
}

func (pool *hostConnPool) initConnPicker(conn *Conn) {
	if _, ok := pool.connPicker.(nopConnPicker); !ok {
		return
	}

	if isScyllaConn(conn) {
		pool.connPicker = newScyllaConnPicker(conn)
		return
	}

	pool.connPicker = newDefaultConnPicker(pool.size)
}

// handle any error from a Conn
func (pool *hostConnPool) HandleError(conn *Conn, err error, closed bool) {
	if !closed {
		// still an open connection, so continue using it
		return
	}

	// TODO: track the number of errors per host and detect when a host is dead,
	// then also have something which can detect when a host comes back.
	pool.mu.Lock()
	defer pool.mu.Unlock()

	if pool.closed {
		// pool closed
		return
	}

	if gocqlDebug {
		pool.logger.Printf("gocql: pool connection error %q: %v\n", conn.addr, err)
	}

	pool.connPicker.Remove(conn)
	go pool.fill_debounce()
}