Don Newton | 379ae25 | 2019-04-01 12:17:06 -0400 | [diff] [blame^] | 1 | // Copyright (C) MongoDB, Inc. 2017-present. |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may |
| 4 | // not use this file except in compliance with the License. You may obtain |
| 5 | // a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 |
| 6 | |
| 7 | package topology |
| 8 | |
| 9 | import ( |
| 10 | "context" |
| 11 | "errors" |
| 12 | "fmt" |
| 13 | "math" |
| 14 | "sync" |
| 15 | "sync/atomic" |
| 16 | "time" |
| 17 | |
| 18 | "github.com/mongodb/mongo-go-driver/event" |
| 19 | "github.com/mongodb/mongo-go-driver/x/mongo/driver/auth" |
| 20 | "github.com/mongodb/mongo-go-driver/x/network/address" |
| 21 | "github.com/mongodb/mongo-go-driver/x/network/command" |
| 22 | "github.com/mongodb/mongo-go-driver/x/network/connection" |
| 23 | "github.com/mongodb/mongo-go-driver/x/network/description" |
| 24 | ) |
| 25 | |
| 26 | const minHeartbeatInterval = 500 * time.Millisecond |
| 27 | const connectionSemaphoreSize = math.MaxInt64 |
| 28 | |
| 29 | // ErrServerClosed occurs when an attempt to get a connection is made after |
| 30 | // the server has been closed. |
| 31 | var ErrServerClosed = errors.New("server is closed") |
| 32 | |
| 33 | // ErrServerConnected occurs when at attempt to connect is made after a server |
| 34 | // has already been connected. |
| 35 | var ErrServerConnected = errors.New("server is connected") |
| 36 | |
| 37 | // SelectedServer represents a specific server that was selected during server selection. |
| 38 | // It contains the kind of the typology it was selected from. |
| 39 | type SelectedServer struct { |
| 40 | *Server |
| 41 | |
| 42 | Kind description.TopologyKind |
| 43 | } |
| 44 | |
| 45 | // Description returns a description of the server as of the last heartbeat. |
| 46 | func (ss *SelectedServer) Description() description.SelectedServer { |
| 47 | sdesc := ss.Server.Description() |
| 48 | return description.SelectedServer{ |
| 49 | Server: sdesc, |
| 50 | Kind: ss.Kind, |
| 51 | } |
| 52 | } |
| 53 | |
| 54 | // These constants represent the connection states of a server. |
| 55 | const ( |
| 56 | disconnected int32 = iota |
| 57 | disconnecting |
| 58 | connected |
| 59 | connecting |
| 60 | ) |
| 61 | |
| 62 | func connectionStateString(state int32) string { |
| 63 | switch state { |
| 64 | case 0: |
| 65 | return "Disconnected" |
| 66 | case 1: |
| 67 | return "Disconnecting" |
| 68 | case 2: |
| 69 | return "Connected" |
| 70 | case 3: |
| 71 | return "Connecting" |
| 72 | } |
| 73 | |
| 74 | return "" |
| 75 | } |
| 76 | |
| 77 | // Server is a single server within a topology. |
| 78 | type Server struct { |
| 79 | cfg *serverConfig |
| 80 | address address.Address |
| 81 | |
| 82 | connectionstate int32 |
| 83 | done chan struct{} |
| 84 | checkNow chan struct{} |
| 85 | closewg sync.WaitGroup |
| 86 | pool connection.Pool |
| 87 | |
| 88 | desc atomic.Value // holds a description.Server |
| 89 | |
| 90 | averageRTTSet bool |
| 91 | averageRTT time.Duration |
| 92 | |
| 93 | subLock sync.Mutex |
| 94 | subscribers map[uint64]chan description.Server |
| 95 | currentSubscriberID uint64 |
| 96 | |
| 97 | subscriptionsClosed bool |
| 98 | } |
| 99 | |
| 100 | // ConnectServer creates a new Server and then initializes it using the |
| 101 | // Connect method. |
| 102 | func ConnectServer(ctx context.Context, addr address.Address, opts ...ServerOption) (*Server, error) { |
| 103 | srvr, err := NewServer(addr, opts...) |
| 104 | if err != nil { |
| 105 | return nil, err |
| 106 | } |
| 107 | err = srvr.Connect(ctx) |
| 108 | if err != nil { |
| 109 | return nil, err |
| 110 | } |
| 111 | return srvr, nil |
| 112 | } |
| 113 | |
| 114 | // NewServer creates a new server. The mongodb server at the address will be monitored |
| 115 | // on an internal monitoring goroutine. |
| 116 | func NewServer(addr address.Address, opts ...ServerOption) (*Server, error) { |
| 117 | cfg, err := newServerConfig(opts...) |
| 118 | if err != nil { |
| 119 | return nil, err |
| 120 | } |
| 121 | |
| 122 | s := &Server{ |
| 123 | cfg: cfg, |
| 124 | address: addr, |
| 125 | |
| 126 | done: make(chan struct{}), |
| 127 | checkNow: make(chan struct{}, 1), |
| 128 | |
| 129 | subscribers: make(map[uint64]chan description.Server), |
| 130 | } |
| 131 | s.desc.Store(description.Server{Addr: addr}) |
| 132 | |
| 133 | var maxConns uint64 |
| 134 | if cfg.maxConns == 0 { |
| 135 | maxConns = math.MaxInt64 |
| 136 | } else { |
| 137 | maxConns = uint64(cfg.maxConns) |
| 138 | } |
| 139 | |
| 140 | s.pool, err = connection.NewPool(addr, uint64(cfg.maxIdleConns), maxConns, cfg.connectionOpts...) |
| 141 | if err != nil { |
| 142 | return nil, err |
| 143 | } |
| 144 | |
| 145 | return s, nil |
| 146 | } |
| 147 | |
| 148 | // Connect initialzies the Server by starting background monitoring goroutines. |
| 149 | // This method must be called before a Server can be used. |
| 150 | func (s *Server) Connect(ctx context.Context) error { |
| 151 | if !atomic.CompareAndSwapInt32(&s.connectionstate, disconnected, connected) { |
| 152 | return ErrServerConnected |
| 153 | } |
| 154 | s.desc.Store(description.Server{Addr: s.address}) |
| 155 | go s.update() |
| 156 | s.closewg.Add(1) |
| 157 | return s.pool.Connect(ctx) |
| 158 | } |
| 159 | |
| 160 | // Disconnect closes sockets to the server referenced by this Server. |
| 161 | // Subscriptions to this Server will be closed. Disconnect will shutdown |
| 162 | // any monitoring goroutines, close the idle connection pool, and will |
| 163 | // wait until all the in use connections have been returned to the connection |
| 164 | // pool and are closed before returning. If the context expires via |
| 165 | // cancellation, deadline, or timeout before the in use connections have been |
| 166 | // returned, the in use connections will be closed, resulting in the failure of |
| 167 | // any in flight read or write operations. If this method returns with no |
| 168 | // errors, all connections associated with this Server have been closed. |
| 169 | func (s *Server) Disconnect(ctx context.Context) error { |
| 170 | if !atomic.CompareAndSwapInt32(&s.connectionstate, connected, disconnecting) { |
| 171 | return ErrServerClosed |
| 172 | } |
| 173 | |
| 174 | // For every call to Connect there must be at least 1 goroutine that is |
| 175 | // waiting on the done channel. |
| 176 | s.done <- struct{}{} |
| 177 | err := s.pool.Disconnect(ctx) |
| 178 | if err != nil { |
| 179 | return err |
| 180 | } |
| 181 | |
| 182 | s.closewg.Wait() |
| 183 | atomic.StoreInt32(&s.connectionstate, disconnected) |
| 184 | |
| 185 | return nil |
| 186 | } |
| 187 | |
| 188 | // Connection gets a connection to the server. |
| 189 | func (s *Server) Connection(ctx context.Context) (connection.Connection, error) { |
| 190 | if atomic.LoadInt32(&s.connectionstate) != connected { |
| 191 | return nil, ErrServerClosed |
| 192 | } |
| 193 | conn, desc, err := s.pool.Get(ctx) |
| 194 | if err != nil { |
| 195 | if _, ok := err.(*auth.Error); ok { |
| 196 | // authentication error --> drain connection |
| 197 | _ = s.pool.Drain() |
| 198 | } |
| 199 | if _, ok := err.(*connection.NetworkError); ok { |
| 200 | // update description to unknown and clears the connection pool |
| 201 | if desc != nil { |
| 202 | desc.Kind = description.Unknown |
| 203 | desc.LastError = err |
| 204 | s.updateDescription(*desc, false) |
| 205 | } else { |
| 206 | _ = s.pool.Drain() |
| 207 | } |
| 208 | } |
| 209 | return nil, err |
| 210 | } |
| 211 | if desc != nil { |
| 212 | go s.updateDescription(*desc, false) |
| 213 | } |
| 214 | sc := &sconn{Connection: conn, s: s} |
| 215 | return sc, nil |
| 216 | } |
| 217 | |
| 218 | // Description returns a description of the server as of the last heartbeat. |
| 219 | func (s *Server) Description() description.Server { |
| 220 | return s.desc.Load().(description.Server) |
| 221 | } |
| 222 | |
| 223 | // SelectedDescription returns a description.SelectedServer with a Kind of |
| 224 | // Single. This can be used when performing tasks like monitoring a batch |
| 225 | // of servers and you want to run one off commands against those servers. |
| 226 | func (s *Server) SelectedDescription() description.SelectedServer { |
| 227 | sdesc := s.Description() |
| 228 | return description.SelectedServer{ |
| 229 | Server: sdesc, |
| 230 | Kind: description.Single, |
| 231 | } |
| 232 | } |
| 233 | |
| 234 | // Subscribe returns a ServerSubscription which has a channel on which all |
| 235 | // updated server descriptions will be sent. The channel will have a buffer |
| 236 | // size of one, and will be pre-populated with the current description. |
| 237 | func (s *Server) Subscribe() (*ServerSubscription, error) { |
| 238 | if atomic.LoadInt32(&s.connectionstate) != connected { |
| 239 | return nil, ErrSubscribeAfterClosed |
| 240 | } |
| 241 | ch := make(chan description.Server, 1) |
| 242 | ch <- s.desc.Load().(description.Server) |
| 243 | |
| 244 | s.subLock.Lock() |
| 245 | defer s.subLock.Unlock() |
| 246 | if s.subscriptionsClosed { |
| 247 | return nil, ErrSubscribeAfterClosed |
| 248 | } |
| 249 | id := s.currentSubscriberID |
| 250 | s.subscribers[id] = ch |
| 251 | s.currentSubscriberID++ |
| 252 | |
| 253 | ss := &ServerSubscription{ |
| 254 | C: ch, |
| 255 | s: s, |
| 256 | id: id, |
| 257 | } |
| 258 | |
| 259 | return ss, nil |
| 260 | } |
| 261 | |
| 262 | // RequestImmediateCheck will cause the server to send a heartbeat immediately |
| 263 | // instead of waiting for the heartbeat timeout. |
| 264 | func (s *Server) RequestImmediateCheck() { |
| 265 | select { |
| 266 | case s.checkNow <- struct{}{}: |
| 267 | default: |
| 268 | } |
| 269 | } |
| 270 | |
| 271 | // update handles performing heartbeats and updating any subscribers of the |
| 272 | // newest description.Server retrieved. |
| 273 | func (s *Server) update() { |
| 274 | defer s.closewg.Done() |
| 275 | heartbeatTicker := time.NewTicker(s.cfg.heartbeatInterval) |
| 276 | rateLimiter := time.NewTicker(minHeartbeatInterval) |
| 277 | defer heartbeatTicker.Stop() |
| 278 | defer rateLimiter.Stop() |
| 279 | checkNow := s.checkNow |
| 280 | done := s.done |
| 281 | |
| 282 | var doneOnce bool |
| 283 | defer func() { |
| 284 | if r := recover(); r != nil { |
| 285 | if doneOnce { |
| 286 | return |
| 287 | } |
| 288 | // We keep this goroutine alive attempting to read from the done channel. |
| 289 | <-done |
| 290 | } |
| 291 | }() |
| 292 | |
| 293 | var conn connection.Connection |
| 294 | var desc description.Server |
| 295 | |
| 296 | desc, conn = s.heartbeat(nil) |
| 297 | s.updateDescription(desc, true) |
| 298 | |
| 299 | closeServer := func() { |
| 300 | doneOnce = true |
| 301 | s.subLock.Lock() |
| 302 | for id, c := range s.subscribers { |
| 303 | close(c) |
| 304 | delete(s.subscribers, id) |
| 305 | } |
| 306 | s.subscriptionsClosed = true |
| 307 | s.subLock.Unlock() |
| 308 | if conn == nil { |
| 309 | return |
| 310 | } |
| 311 | conn.Close() |
| 312 | } |
| 313 | for { |
| 314 | select { |
| 315 | case <-heartbeatTicker.C: |
| 316 | case <-checkNow: |
| 317 | case <-done: |
| 318 | closeServer() |
| 319 | return |
| 320 | } |
| 321 | |
| 322 | select { |
| 323 | case <-rateLimiter.C: |
| 324 | case <-done: |
| 325 | closeServer() |
| 326 | return |
| 327 | } |
| 328 | |
| 329 | desc, conn = s.heartbeat(conn) |
| 330 | s.updateDescription(desc, false) |
| 331 | } |
| 332 | } |
| 333 | |
| 334 | // updateDescription handles updating the description on the Server, notifying |
| 335 | // subscribers, and potentially draining the connection pool. The initial |
| 336 | // parameter is used to determine if this is the first description from the |
| 337 | // server. |
| 338 | func (s *Server) updateDescription(desc description.Server, initial bool) { |
| 339 | defer func() { |
| 340 | // ¯\_(ツ)_/¯ |
| 341 | _ = recover() |
| 342 | }() |
| 343 | s.desc.Store(desc) |
| 344 | |
| 345 | s.subLock.Lock() |
| 346 | for _, c := range s.subscribers { |
| 347 | select { |
| 348 | // drain the channel if it isn't empty |
| 349 | case <-c: |
| 350 | default: |
| 351 | } |
| 352 | c <- desc |
| 353 | } |
| 354 | s.subLock.Unlock() |
| 355 | |
| 356 | if initial { |
| 357 | // We don't clear the pool on the first update on the description. |
| 358 | return |
| 359 | } |
| 360 | |
| 361 | switch desc.Kind { |
| 362 | case description.Unknown: |
| 363 | _ = s.pool.Drain() |
| 364 | } |
| 365 | } |
| 366 | |
| 367 | // heartbeat sends a heartbeat to the server using the given connection. The connection can be nil. |
| 368 | func (s *Server) heartbeat(conn connection.Connection) (description.Server, connection.Connection) { |
| 369 | const maxRetry = 2 |
| 370 | var saved error |
| 371 | var desc description.Server |
| 372 | var set bool |
| 373 | var err error |
| 374 | ctx := context.Background() |
| 375 | |
| 376 | for i := 1; i <= maxRetry; i++ { |
| 377 | if conn != nil && conn.Expired() { |
| 378 | conn.Close() |
| 379 | conn = nil |
| 380 | } |
| 381 | |
| 382 | if conn == nil { |
| 383 | opts := []connection.Option{ |
| 384 | connection.WithConnectTimeout(func(time.Duration) time.Duration { return s.cfg.heartbeatTimeout }), |
| 385 | connection.WithReadTimeout(func(time.Duration) time.Duration { return s.cfg.heartbeatTimeout }), |
| 386 | connection.WithWriteTimeout(func(time.Duration) time.Duration { return s.cfg.heartbeatTimeout }), |
| 387 | } |
| 388 | opts = append(opts, s.cfg.connectionOpts...) |
| 389 | // We override whatever handshaker is currently attached to the options with an empty |
| 390 | // one because need to make sure we don't do auth. |
| 391 | opts = append(opts, connection.WithHandshaker(func(h connection.Handshaker) connection.Handshaker { |
| 392 | return nil |
| 393 | })) |
| 394 | |
| 395 | // Override any command monitors specified in options with nil to avoid monitoring heartbeats. |
| 396 | opts = append(opts, connection.WithMonitor(func(*event.CommandMonitor) *event.CommandMonitor { |
| 397 | return nil |
| 398 | })) |
| 399 | conn, _, err = connection.New(ctx, s.address, opts...) |
| 400 | if err != nil { |
| 401 | saved = err |
| 402 | if conn != nil { |
| 403 | conn.Close() |
| 404 | } |
| 405 | conn = nil |
| 406 | continue |
| 407 | } |
| 408 | } |
| 409 | |
| 410 | now := time.Now() |
| 411 | |
| 412 | isMasterCmd := &command.IsMaster{Compressors: s.cfg.compressionOpts} |
| 413 | isMaster, err := isMasterCmd.RoundTrip(ctx, conn) |
| 414 | if err != nil { |
| 415 | saved = err |
| 416 | conn.Close() |
| 417 | conn = nil |
| 418 | continue |
| 419 | } |
| 420 | |
| 421 | clusterTime := isMaster.ClusterTime |
| 422 | if s.cfg.clock != nil { |
| 423 | s.cfg.clock.AdvanceClusterTime(clusterTime) |
| 424 | } |
| 425 | |
| 426 | delay := time.Since(now) |
| 427 | desc = description.NewServer(s.address, isMaster).SetAverageRTT(s.updateAverageRTT(delay)) |
| 428 | desc.HeartbeatInterval = s.cfg.heartbeatInterval |
| 429 | set = true |
| 430 | |
| 431 | break |
| 432 | } |
| 433 | |
| 434 | if !set { |
| 435 | desc = description.Server{ |
| 436 | Addr: s.address, |
| 437 | LastError: saved, |
| 438 | } |
| 439 | } |
| 440 | |
| 441 | return desc, conn |
| 442 | } |
| 443 | |
| 444 | func (s *Server) updateAverageRTT(delay time.Duration) time.Duration { |
| 445 | if !s.averageRTTSet { |
| 446 | s.averageRTT = delay |
| 447 | } else { |
| 448 | alpha := 0.2 |
| 449 | s.averageRTT = time.Duration(alpha*float64(delay) + (1-alpha)*float64(s.averageRTT)) |
| 450 | } |
| 451 | return s.averageRTT |
| 452 | } |
| 453 | |
| 454 | // Drain will drain the connection pool of this server. This is mainly here so the |
| 455 | // pool for the server doesn't need to be directly exposed and so that when an error |
| 456 | // is returned from reading or writing, a client can drain the pool for this server. |
| 457 | // This is exposed here so we don't have to wrap the Connection type and sniff responses |
| 458 | // for errors that would cause the pool to be drained, which can in turn centralize the |
| 459 | // logic for handling errors in the Client type. |
| 460 | func (s *Server) Drain() error { return s.pool.Drain() } |
| 461 | |
| 462 | // String implements the Stringer interface. |
| 463 | func (s *Server) String() string { |
| 464 | desc := s.Description() |
| 465 | str := fmt.Sprintf("Addr: %s, Type: %s, State: %s", |
| 466 | s.address, desc.Kind, connectionStateString(s.connectionstate)) |
| 467 | if len(desc.Tags) != 0 { |
| 468 | str += fmt.Sprintf(", Tag sets: %s", desc.Tags) |
| 469 | } |
| 470 | if s.connectionstate == connected { |
| 471 | str += fmt.Sprintf(", Avergage RTT: %d", s.averageRTT) |
| 472 | } |
| 473 | if desc.LastError != nil { |
| 474 | str += fmt.Sprintf(", Last error: %s", desc.LastError) |
| 475 | } |
| 476 | |
| 477 | return str |
| 478 | } |
| 479 | |
| 480 | // ServerSubscription represents a subscription to the description.Server updates for |
| 481 | // a specific server. |
| 482 | type ServerSubscription struct { |
| 483 | C <-chan description.Server |
| 484 | s *Server |
| 485 | id uint64 |
| 486 | } |
| 487 | |
| 488 | // Unsubscribe unsubscribes this ServerSubscription from updates and closes the |
| 489 | // subscription channel. |
| 490 | func (ss *ServerSubscription) Unsubscribe() error { |
| 491 | ss.s.subLock.Lock() |
| 492 | defer ss.s.subLock.Unlock() |
| 493 | if ss.s.subscriptionsClosed { |
| 494 | return nil |
| 495 | } |
| 496 | |
| 497 | ch, ok := ss.s.subscribers[ss.id] |
| 498 | if !ok { |
| 499 | return nil |
| 500 | } |
| 501 | |
| 502 | close(ch) |
| 503 | delete(ss.s.subscribers, ss.id) |
| 504 | |
| 505 | return nil |
| 506 | } |