| // Copyright (C) MongoDB, Inc. 2017-present. |
| // |
| // 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 |
| |
| package topology |
| |
| import ( |
| "context" |
| "errors" |
| "fmt" |
| "math" |
| "sync" |
| "sync/atomic" |
| "time" |
| |
| "github.com/mongodb/mongo-go-driver/event" |
| "github.com/mongodb/mongo-go-driver/x/mongo/driver/auth" |
| "github.com/mongodb/mongo-go-driver/x/network/address" |
| "github.com/mongodb/mongo-go-driver/x/network/command" |
| "github.com/mongodb/mongo-go-driver/x/network/connection" |
| "github.com/mongodb/mongo-go-driver/x/network/description" |
| ) |
| |
| const minHeartbeatInterval = 500 * time.Millisecond |
| const connectionSemaphoreSize = math.MaxInt64 |
| |
| // ErrServerClosed occurs when an attempt to get a connection is made after |
| // the server has been closed. |
| var ErrServerClosed = errors.New("server is closed") |
| |
| // ErrServerConnected occurs when at attempt to connect is made after a server |
| // has already been connected. |
| var ErrServerConnected = errors.New("server is connected") |
| |
| // SelectedServer represents a specific server that was selected during server selection. |
| // It contains the kind of the typology it was selected from. |
| type SelectedServer struct { |
| *Server |
| |
| Kind description.TopologyKind |
| } |
| |
| // Description returns a description of the server as of the last heartbeat. |
| func (ss *SelectedServer) Description() description.SelectedServer { |
| sdesc := ss.Server.Description() |
| return description.SelectedServer{ |
| Server: sdesc, |
| Kind: ss.Kind, |
| } |
| } |
| |
| // These constants represent the connection states of a server. |
| const ( |
| disconnected int32 = iota |
| disconnecting |
| connected |
| connecting |
| ) |
| |
| func connectionStateString(state int32) string { |
| switch state { |
| case 0: |
| return "Disconnected" |
| case 1: |
| return "Disconnecting" |
| case 2: |
| return "Connected" |
| case 3: |
| return "Connecting" |
| } |
| |
| return "" |
| } |
| |
| // Server is a single server within a topology. |
| type Server struct { |
| cfg *serverConfig |
| address address.Address |
| |
| connectionstate int32 |
| done chan struct{} |
| checkNow chan struct{} |
| closewg sync.WaitGroup |
| pool connection.Pool |
| |
| desc atomic.Value // holds a description.Server |
| |
| averageRTTSet bool |
| averageRTT time.Duration |
| |
| subLock sync.Mutex |
| subscribers map[uint64]chan description.Server |
| currentSubscriberID uint64 |
| |
| subscriptionsClosed bool |
| } |
| |
| // ConnectServer creates a new Server and then initializes it using the |
| // Connect method. |
| func ConnectServer(ctx context.Context, addr address.Address, opts ...ServerOption) (*Server, error) { |
| srvr, err := NewServer(addr, opts...) |
| if err != nil { |
| return nil, err |
| } |
| err = srvr.Connect(ctx) |
| if err != nil { |
| return nil, err |
| } |
| return srvr, nil |
| } |
| |
| // NewServer creates a new server. The mongodb server at the address will be monitored |
| // on an internal monitoring goroutine. |
| func NewServer(addr address.Address, opts ...ServerOption) (*Server, error) { |
| cfg, err := newServerConfig(opts...) |
| if err != nil { |
| return nil, err |
| } |
| |
| s := &Server{ |
| cfg: cfg, |
| address: addr, |
| |
| done: make(chan struct{}), |
| checkNow: make(chan struct{}, 1), |
| |
| subscribers: make(map[uint64]chan description.Server), |
| } |
| s.desc.Store(description.Server{Addr: addr}) |
| |
| var maxConns uint64 |
| if cfg.maxConns == 0 { |
| maxConns = math.MaxInt64 |
| } else { |
| maxConns = uint64(cfg.maxConns) |
| } |
| |
| s.pool, err = connection.NewPool(addr, uint64(cfg.maxIdleConns), maxConns, cfg.connectionOpts...) |
| if err != nil { |
| return nil, err |
| } |
| |
| return s, nil |
| } |
| |
| // Connect initialzies the Server by starting background monitoring goroutines. |
| // This method must be called before a Server can be used. |
| func (s *Server) Connect(ctx context.Context) error { |
| if !atomic.CompareAndSwapInt32(&s.connectionstate, disconnected, connected) { |
| return ErrServerConnected |
| } |
| s.desc.Store(description.Server{Addr: s.address}) |
| go s.update() |
| s.closewg.Add(1) |
| return s.pool.Connect(ctx) |
| } |
| |
| // Disconnect closes sockets to the server referenced by this Server. |
| // Subscriptions to this Server will be closed. Disconnect will shutdown |
| // any monitoring goroutines, close the idle connection pool, and will |
| // wait until all the in use connections have been returned to the connection |
| // pool and are closed before returning. If the context expires via |
| // cancellation, deadline, or timeout before the in use connections have been |
| // returned, the in use connections will be closed, resulting in the failure of |
| // any in flight read or write operations. If this method returns with no |
| // errors, all connections associated with this Server have been closed. |
| func (s *Server) Disconnect(ctx context.Context) error { |
| if !atomic.CompareAndSwapInt32(&s.connectionstate, connected, disconnecting) { |
| return ErrServerClosed |
| } |
| |
| // For every call to Connect there must be at least 1 goroutine that is |
| // waiting on the done channel. |
| s.done <- struct{}{} |
| err := s.pool.Disconnect(ctx) |
| if err != nil { |
| return err |
| } |
| |
| s.closewg.Wait() |
| atomic.StoreInt32(&s.connectionstate, disconnected) |
| |
| return nil |
| } |
| |
| // Connection gets a connection to the server. |
| func (s *Server) Connection(ctx context.Context) (connection.Connection, error) { |
| if atomic.LoadInt32(&s.connectionstate) != connected { |
| return nil, ErrServerClosed |
| } |
| conn, desc, err := s.pool.Get(ctx) |
| if err != nil { |
| if _, ok := err.(*auth.Error); ok { |
| // authentication error --> drain connection |
| _ = s.pool.Drain() |
| } |
| if _, ok := err.(*connection.NetworkError); ok { |
| // update description to unknown and clears the connection pool |
| if desc != nil { |
| desc.Kind = description.Unknown |
| desc.LastError = err |
| s.updateDescription(*desc, false) |
| } else { |
| _ = s.pool.Drain() |
| } |
| } |
| return nil, err |
| } |
| if desc != nil { |
| go s.updateDescription(*desc, false) |
| } |
| sc := &sconn{Connection: conn, s: s} |
| return sc, nil |
| } |
| |
| // Description returns a description of the server as of the last heartbeat. |
| func (s *Server) Description() description.Server { |
| return s.desc.Load().(description.Server) |
| } |
| |
| // SelectedDescription returns a description.SelectedServer with a Kind of |
| // Single. This can be used when performing tasks like monitoring a batch |
| // of servers and you want to run one off commands against those servers. |
| func (s *Server) SelectedDescription() description.SelectedServer { |
| sdesc := s.Description() |
| return description.SelectedServer{ |
| Server: sdesc, |
| Kind: description.Single, |
| } |
| } |
| |
| // Subscribe returns a ServerSubscription which has a channel on which all |
| // updated server descriptions will be sent. The channel will have a buffer |
| // size of one, and will be pre-populated with the current description. |
| func (s *Server) Subscribe() (*ServerSubscription, error) { |
| if atomic.LoadInt32(&s.connectionstate) != connected { |
| return nil, ErrSubscribeAfterClosed |
| } |
| ch := make(chan description.Server, 1) |
| ch <- s.desc.Load().(description.Server) |
| |
| s.subLock.Lock() |
| defer s.subLock.Unlock() |
| if s.subscriptionsClosed { |
| return nil, ErrSubscribeAfterClosed |
| } |
| id := s.currentSubscriberID |
| s.subscribers[id] = ch |
| s.currentSubscriberID++ |
| |
| ss := &ServerSubscription{ |
| C: ch, |
| s: s, |
| id: id, |
| } |
| |
| return ss, nil |
| } |
| |
| // RequestImmediateCheck will cause the server to send a heartbeat immediately |
| // instead of waiting for the heartbeat timeout. |
| func (s *Server) RequestImmediateCheck() { |
| select { |
| case s.checkNow <- struct{}{}: |
| default: |
| } |
| } |
| |
| // update handles performing heartbeats and updating any subscribers of the |
| // newest description.Server retrieved. |
| func (s *Server) update() { |
| defer s.closewg.Done() |
| heartbeatTicker := time.NewTicker(s.cfg.heartbeatInterval) |
| rateLimiter := time.NewTicker(minHeartbeatInterval) |
| defer heartbeatTicker.Stop() |
| defer rateLimiter.Stop() |
| checkNow := s.checkNow |
| done := s.done |
| |
| var doneOnce bool |
| defer func() { |
| if r := recover(); r != nil { |
| if doneOnce { |
| return |
| } |
| // We keep this goroutine alive attempting to read from the done channel. |
| <-done |
| } |
| }() |
| |
| var conn connection.Connection |
| var desc description.Server |
| |
| desc, conn = s.heartbeat(nil) |
| s.updateDescription(desc, true) |
| |
| closeServer := func() { |
| doneOnce = true |
| s.subLock.Lock() |
| for id, c := range s.subscribers { |
| close(c) |
| delete(s.subscribers, id) |
| } |
| s.subscriptionsClosed = true |
| s.subLock.Unlock() |
| if conn == nil { |
| return |
| } |
| conn.Close() |
| } |
| for { |
| select { |
| case <-heartbeatTicker.C: |
| case <-checkNow: |
| case <-done: |
| closeServer() |
| return |
| } |
| |
| select { |
| case <-rateLimiter.C: |
| case <-done: |
| closeServer() |
| return |
| } |
| |
| desc, conn = s.heartbeat(conn) |
| s.updateDescription(desc, false) |
| } |
| } |
| |
| // updateDescription handles updating the description on the Server, notifying |
| // subscribers, and potentially draining the connection pool. The initial |
| // parameter is used to determine if this is the first description from the |
| // server. |
| func (s *Server) updateDescription(desc description.Server, initial bool) { |
| defer func() { |
| // ¯\_(ツ)_/¯ |
| _ = recover() |
| }() |
| s.desc.Store(desc) |
| |
| s.subLock.Lock() |
| for _, c := range s.subscribers { |
| select { |
| // drain the channel if it isn't empty |
| case <-c: |
| default: |
| } |
| c <- desc |
| } |
| s.subLock.Unlock() |
| |
| if initial { |
| // We don't clear the pool on the first update on the description. |
| return |
| } |
| |
| switch desc.Kind { |
| case description.Unknown: |
| _ = s.pool.Drain() |
| } |
| } |
| |
| // heartbeat sends a heartbeat to the server using the given connection. The connection can be nil. |
| func (s *Server) heartbeat(conn connection.Connection) (description.Server, connection.Connection) { |
| const maxRetry = 2 |
| var saved error |
| var desc description.Server |
| var set bool |
| var err error |
| ctx := context.Background() |
| |
| for i := 1; i <= maxRetry; i++ { |
| if conn != nil && conn.Expired() { |
| conn.Close() |
| conn = nil |
| } |
| |
| if conn == nil { |
| opts := []connection.Option{ |
| connection.WithConnectTimeout(func(time.Duration) time.Duration { return s.cfg.heartbeatTimeout }), |
| connection.WithReadTimeout(func(time.Duration) time.Duration { return s.cfg.heartbeatTimeout }), |
| connection.WithWriteTimeout(func(time.Duration) time.Duration { return s.cfg.heartbeatTimeout }), |
| } |
| opts = append(opts, s.cfg.connectionOpts...) |
| // We override whatever handshaker is currently attached to the options with an empty |
| // one because need to make sure we don't do auth. |
| opts = append(opts, connection.WithHandshaker(func(h connection.Handshaker) connection.Handshaker { |
| return nil |
| })) |
| |
| // Override any command monitors specified in options with nil to avoid monitoring heartbeats. |
| opts = append(opts, connection.WithMonitor(func(*event.CommandMonitor) *event.CommandMonitor { |
| return nil |
| })) |
| conn, _, err = connection.New(ctx, s.address, opts...) |
| if err != nil { |
| saved = err |
| if conn != nil { |
| conn.Close() |
| } |
| conn = nil |
| continue |
| } |
| } |
| |
| now := time.Now() |
| |
| isMasterCmd := &command.IsMaster{Compressors: s.cfg.compressionOpts} |
| isMaster, err := isMasterCmd.RoundTrip(ctx, conn) |
| if err != nil { |
| saved = err |
| conn.Close() |
| conn = nil |
| continue |
| } |
| |
| clusterTime := isMaster.ClusterTime |
| if s.cfg.clock != nil { |
| s.cfg.clock.AdvanceClusterTime(clusterTime) |
| } |
| |
| delay := time.Since(now) |
| desc = description.NewServer(s.address, isMaster).SetAverageRTT(s.updateAverageRTT(delay)) |
| desc.HeartbeatInterval = s.cfg.heartbeatInterval |
| set = true |
| |
| break |
| } |
| |
| if !set { |
| desc = description.Server{ |
| Addr: s.address, |
| LastError: saved, |
| } |
| } |
| |
| return desc, conn |
| } |
| |
| func (s *Server) updateAverageRTT(delay time.Duration) time.Duration { |
| if !s.averageRTTSet { |
| s.averageRTT = delay |
| } else { |
| alpha := 0.2 |
| s.averageRTT = time.Duration(alpha*float64(delay) + (1-alpha)*float64(s.averageRTT)) |
| } |
| return s.averageRTT |
| } |
| |
| // Drain will drain the connection pool of this server. This is mainly here so the |
| // pool for the server doesn't need to be directly exposed and so that when an error |
| // is returned from reading or writing, a client can drain the pool for this server. |
| // This is exposed here so we don't have to wrap the Connection type and sniff responses |
| // for errors that would cause the pool to be drained, which can in turn centralize the |
| // logic for handling errors in the Client type. |
| func (s *Server) Drain() error { return s.pool.Drain() } |
| |
| // String implements the Stringer interface. |
| func (s *Server) String() string { |
| desc := s.Description() |
| str := fmt.Sprintf("Addr: %s, Type: %s, State: %s", |
| s.address, desc.Kind, connectionStateString(s.connectionstate)) |
| if len(desc.Tags) != 0 { |
| str += fmt.Sprintf(", Tag sets: %s", desc.Tags) |
| } |
| if s.connectionstate == connected { |
| str += fmt.Sprintf(", Avergage RTT: %d", s.averageRTT) |
| } |
| if desc.LastError != nil { |
| str += fmt.Sprintf(", Last error: %s", desc.LastError) |
| } |
| |
| return str |
| } |
| |
| // ServerSubscription represents a subscription to the description.Server updates for |
| // a specific server. |
| type ServerSubscription struct { |
| C <-chan description.Server |
| s *Server |
| id uint64 |
| } |
| |
| // Unsubscribe unsubscribes this ServerSubscription from updates and closes the |
| // subscription channel. |
| func (ss *ServerSubscription) Unsubscribe() error { |
| ss.s.subLock.Lock() |
| defer ss.s.subLock.Unlock() |
| if ss.s.subscriptionsClosed { |
| return nil |
| } |
| |
| ch, ok := ss.s.subscribers[ss.id] |
| if !ok { |
| return nil |
| } |
| |
| close(ch) |
| delete(ss.s.subscribers, ss.id) |
| |
| return nil |
| } |