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 session |
| 8 | |
| 9 | import ( |
| 10 | "errors" |
| 11 | |
| 12 | "github.com/mongodb/mongo-go-driver/bson" |
| 13 | "github.com/mongodb/mongo-go-driver/bson/primitive" |
| 14 | "github.com/mongodb/mongo-go-driver/mongo/readconcern" |
| 15 | "github.com/mongodb/mongo-go-driver/mongo/readpref" |
| 16 | "github.com/mongodb/mongo-go-driver/mongo/writeconcern" |
| 17 | "github.com/mongodb/mongo-go-driver/x/mongo/driver/uuid" |
| 18 | ) |
| 19 | |
| 20 | // ErrSessionEnded is returned when a client session is used after a call to endSession(). |
| 21 | var ErrSessionEnded = errors.New("ended session was used") |
| 22 | |
| 23 | // ErrNoTransactStarted is returned if a transaction operation is called when no transaction has started. |
| 24 | var ErrNoTransactStarted = errors.New("no transaction started") |
| 25 | |
| 26 | // ErrTransactInProgress is returned if startTransaction() is called when a transaction is in progress. |
| 27 | var ErrTransactInProgress = errors.New("transaction already in progress") |
| 28 | |
| 29 | // ErrAbortAfterCommit is returned when abort is called after a commit. |
| 30 | var ErrAbortAfterCommit = errors.New("cannot call abortTransaction after calling commitTransaction") |
| 31 | |
| 32 | // ErrAbortTwice is returned if abort is called after transaction is already aborted. |
| 33 | var ErrAbortTwice = errors.New("cannot call abortTransaction twice") |
| 34 | |
| 35 | // ErrCommitAfterAbort is returned if commit is called after an abort. |
| 36 | var ErrCommitAfterAbort = errors.New("cannot call commitTransaction after calling abortTransaction") |
| 37 | |
| 38 | // ErrUnackWCUnsupported is returned if an unacknowledged write concern is supported for a transaciton. |
| 39 | var ErrUnackWCUnsupported = errors.New("transactions do not support unacknowledged write concerns") |
| 40 | |
| 41 | // Type describes the type of the session |
| 42 | type Type uint8 |
| 43 | |
| 44 | // These constants are the valid types for a client session. |
| 45 | const ( |
| 46 | Explicit Type = iota |
| 47 | Implicit |
| 48 | ) |
| 49 | |
| 50 | // State indicates the state of the FSM. |
| 51 | type state uint8 |
| 52 | |
| 53 | // Client Session states |
| 54 | const ( |
| 55 | None state = iota |
| 56 | Starting |
| 57 | InProgress |
| 58 | Committed |
| 59 | Aborted |
| 60 | ) |
| 61 | |
| 62 | // Client is a session for clients to run commands. |
| 63 | type Client struct { |
| 64 | *Server |
| 65 | ClientID uuid.UUID |
| 66 | ClusterTime bson.Raw |
| 67 | Consistent bool // causal consistency |
| 68 | OperationTime *primitive.Timestamp |
| 69 | SessionType Type |
| 70 | Terminated bool |
| 71 | RetryingCommit bool |
| 72 | Committing bool |
| 73 | Aborting bool |
| 74 | RetryWrite bool |
| 75 | |
| 76 | // options for the current transaction |
| 77 | // most recently set by transactionopt |
| 78 | CurrentRc *readconcern.ReadConcern |
| 79 | CurrentRp *readpref.ReadPref |
| 80 | CurrentWc *writeconcern.WriteConcern |
| 81 | |
| 82 | // default transaction options |
| 83 | transactionRc *readconcern.ReadConcern |
| 84 | transactionRp *readpref.ReadPref |
| 85 | transactionWc *writeconcern.WriteConcern |
| 86 | |
| 87 | pool *Pool |
| 88 | state state |
| 89 | } |
| 90 | |
| 91 | func getClusterTime(clusterTime bson.Raw) (uint32, uint32) { |
| 92 | if clusterTime == nil { |
| 93 | return 0, 0 |
| 94 | } |
| 95 | |
| 96 | clusterTimeVal, err := clusterTime.LookupErr("$clusterTime") |
| 97 | if err != nil { |
| 98 | return 0, 0 |
| 99 | } |
| 100 | |
| 101 | timestampVal, err := bson.Raw(clusterTimeVal.Value).LookupErr("clusterTime") |
| 102 | if err != nil { |
| 103 | return 0, 0 |
| 104 | } |
| 105 | |
| 106 | return timestampVal.Timestamp() |
| 107 | } |
| 108 | |
| 109 | // MaxClusterTime compares 2 clusterTime documents and returns the document representing the highest cluster time. |
| 110 | func MaxClusterTime(ct1, ct2 bson.Raw) bson.Raw { |
| 111 | epoch1, ord1 := getClusterTime(ct1) |
| 112 | epoch2, ord2 := getClusterTime(ct2) |
| 113 | |
| 114 | if epoch1 > epoch2 { |
| 115 | return ct1 |
| 116 | } else if epoch1 < epoch2 { |
| 117 | return ct2 |
| 118 | } else if ord1 > ord2 { |
| 119 | return ct1 |
| 120 | } else if ord1 < ord2 { |
| 121 | return ct2 |
| 122 | } |
| 123 | |
| 124 | return ct1 |
| 125 | } |
| 126 | |
| 127 | // NewClientSession creates a Client. |
| 128 | func NewClientSession(pool *Pool, clientID uuid.UUID, sessionType Type, opts ...*ClientOptions) (*Client, error) { |
| 129 | c := &Client{ |
| 130 | Consistent: true, // set default |
| 131 | ClientID: clientID, |
| 132 | SessionType: sessionType, |
| 133 | pool: pool, |
| 134 | } |
| 135 | |
| 136 | mergedOpts := mergeClientOptions(opts...) |
| 137 | if mergedOpts.CausalConsistency != nil { |
| 138 | c.Consistent = *mergedOpts.CausalConsistency |
| 139 | } |
| 140 | if mergedOpts.DefaultReadPreference != nil { |
| 141 | c.transactionRp = mergedOpts.DefaultReadPreference |
| 142 | } |
| 143 | if mergedOpts.DefaultReadConcern != nil { |
| 144 | c.transactionRc = mergedOpts.DefaultReadConcern |
| 145 | } |
| 146 | if mergedOpts.DefaultWriteConcern != nil { |
| 147 | c.transactionWc = mergedOpts.DefaultWriteConcern |
| 148 | } |
| 149 | |
| 150 | servSess, err := pool.GetSession() |
| 151 | if err != nil { |
| 152 | return nil, err |
| 153 | } |
| 154 | |
| 155 | c.Server = servSess |
| 156 | |
| 157 | return c, nil |
| 158 | } |
| 159 | |
| 160 | // AdvanceClusterTime updates the session's cluster time. |
| 161 | func (c *Client) AdvanceClusterTime(clusterTime bson.Raw) error { |
| 162 | if c.Terminated { |
| 163 | return ErrSessionEnded |
| 164 | } |
| 165 | c.ClusterTime = MaxClusterTime(c.ClusterTime, clusterTime) |
| 166 | return nil |
| 167 | } |
| 168 | |
| 169 | // AdvanceOperationTime updates the session's operation time. |
| 170 | func (c *Client) AdvanceOperationTime(opTime *primitive.Timestamp) error { |
| 171 | if c.Terminated { |
| 172 | return ErrSessionEnded |
| 173 | } |
| 174 | |
| 175 | if c.OperationTime == nil { |
| 176 | c.OperationTime = opTime |
| 177 | return nil |
| 178 | } |
| 179 | |
| 180 | if opTime.T > c.OperationTime.T { |
| 181 | c.OperationTime = opTime |
| 182 | } else if (opTime.T == c.OperationTime.T) && (opTime.I > c.OperationTime.I) { |
| 183 | c.OperationTime = opTime |
| 184 | } |
| 185 | |
| 186 | return nil |
| 187 | } |
| 188 | |
| 189 | // UpdateUseTime updates the session's last used time. |
| 190 | // Must be called whenver this session is used to send a command to the server. |
| 191 | func (c *Client) UpdateUseTime() error { |
| 192 | if c.Terminated { |
| 193 | return ErrSessionEnded |
| 194 | } |
| 195 | c.updateUseTime() |
| 196 | return nil |
| 197 | } |
| 198 | |
| 199 | // EndSession ends the session. |
| 200 | func (c *Client) EndSession() { |
| 201 | if c.Terminated { |
| 202 | return |
| 203 | } |
| 204 | |
| 205 | c.Terminated = true |
| 206 | c.pool.ReturnSession(c.Server) |
| 207 | |
| 208 | return |
| 209 | } |
| 210 | |
| 211 | // TransactionInProgress returns true if the client session is in an active transaction. |
| 212 | func (c *Client) TransactionInProgress() bool { |
| 213 | return c.state == InProgress |
| 214 | } |
| 215 | |
| 216 | // TransactionStarting returns true if the client session is starting a transaction. |
| 217 | func (c *Client) TransactionStarting() bool { |
| 218 | return c.state == Starting |
| 219 | } |
| 220 | |
| 221 | // TransactionRunning returns true if the client session has started the transaction |
| 222 | // and it hasn't been committed or aborted |
| 223 | func (c *Client) TransactionRunning() bool { |
| 224 | return c.state == Starting || c.state == InProgress |
| 225 | } |
| 226 | |
| 227 | // TransactionCommitted returns true of the client session just committed a transaciton. |
| 228 | func (c *Client) TransactionCommitted() bool { |
| 229 | return c.state == Committed |
| 230 | } |
| 231 | |
| 232 | // CheckStartTransaction checks to see if allowed to start transaction and returns |
| 233 | // an error if not allowed |
| 234 | func (c *Client) CheckStartTransaction() error { |
| 235 | if c.state == InProgress || c.state == Starting { |
| 236 | return ErrTransactInProgress |
| 237 | } |
| 238 | return nil |
| 239 | } |
| 240 | |
| 241 | // StartTransaction initializes the transaction options and advances the state machine. |
| 242 | // It does not contact the server to start the transaction. |
| 243 | func (c *Client) StartTransaction(opts *TransactionOptions) error { |
| 244 | err := c.CheckStartTransaction() |
| 245 | if err != nil { |
| 246 | return err |
| 247 | } |
| 248 | |
| 249 | c.IncrementTxnNumber() |
| 250 | c.RetryingCommit = false |
| 251 | |
| 252 | if opts != nil { |
| 253 | c.CurrentRc = opts.ReadConcern |
| 254 | c.CurrentRp = opts.ReadPreference |
| 255 | c.CurrentWc = opts.WriteConcern |
| 256 | } |
| 257 | |
| 258 | if c.CurrentRc == nil { |
| 259 | c.CurrentRc = c.transactionRc |
| 260 | } |
| 261 | |
| 262 | if c.CurrentRp == nil { |
| 263 | c.CurrentRp = c.transactionRp |
| 264 | } |
| 265 | |
| 266 | if c.CurrentWc == nil { |
| 267 | c.CurrentWc = c.transactionWc |
| 268 | } |
| 269 | |
| 270 | if !writeconcern.AckWrite(c.CurrentWc) { |
| 271 | c.clearTransactionOpts() |
| 272 | return ErrUnackWCUnsupported |
| 273 | } |
| 274 | |
| 275 | c.state = Starting |
| 276 | return nil |
| 277 | } |
| 278 | |
| 279 | // CheckCommitTransaction checks to see if allowed to commit transaction and returns |
| 280 | // an error if not allowed. |
| 281 | func (c *Client) CheckCommitTransaction() error { |
| 282 | if c.state == None { |
| 283 | return ErrNoTransactStarted |
| 284 | } else if c.state == Aborted { |
| 285 | return ErrCommitAfterAbort |
| 286 | } |
| 287 | return nil |
| 288 | } |
| 289 | |
| 290 | // CommitTransaction updates the state for a successfully committed transaction and returns |
| 291 | // an error if not permissible. It does not actually perform the commit. |
| 292 | func (c *Client) CommitTransaction() error { |
| 293 | err := c.CheckCommitTransaction() |
| 294 | if err != nil { |
| 295 | return err |
| 296 | } |
| 297 | c.state = Committed |
| 298 | return nil |
| 299 | } |
| 300 | |
| 301 | // CheckAbortTransaction checks to see if allowed to abort transaction and returns |
| 302 | // an error if not allowed. |
| 303 | func (c *Client) CheckAbortTransaction() error { |
| 304 | if c.state == None { |
| 305 | return ErrNoTransactStarted |
| 306 | } else if c.state == Committed { |
| 307 | return ErrAbortAfterCommit |
| 308 | } else if c.state == Aborted { |
| 309 | return ErrAbortTwice |
| 310 | } |
| 311 | return nil |
| 312 | } |
| 313 | |
| 314 | // AbortTransaction updates the state for a successfully committed transaction and returns |
| 315 | // an error if not permissible. It does not actually perform the abort. |
| 316 | func (c *Client) AbortTransaction() error { |
| 317 | err := c.CheckAbortTransaction() |
| 318 | if err != nil { |
| 319 | return err |
| 320 | } |
| 321 | c.state = Aborted |
| 322 | c.clearTransactionOpts() |
| 323 | return nil |
| 324 | } |
| 325 | |
| 326 | // ApplyCommand advances the state machine upon command execution. |
| 327 | func (c *Client) ApplyCommand() { |
| 328 | if c.Committing { |
| 329 | // Do not change state if committing after already committed |
| 330 | return |
| 331 | } |
| 332 | if c.state == Starting { |
| 333 | c.state = InProgress |
| 334 | } else if c.state == Committed || c.state == Aborted { |
| 335 | c.clearTransactionOpts() |
| 336 | c.state = None |
| 337 | } |
| 338 | } |
| 339 | |
| 340 | func (c *Client) clearTransactionOpts() { |
| 341 | c.RetryingCommit = false |
| 342 | c.Aborting = false |
| 343 | c.Committing = false |
| 344 | c.CurrentWc = nil |
| 345 | c.CurrentRp = nil |
| 346 | c.CurrentRc = nil |
| 347 | } |