Don Newton | 379ae25 | 2019-04-01 12:17:06 -0400 | [diff] [blame^] | 1 | package driver |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "errors" |
| 6 | "fmt" |
| 7 | |
| 8 | "github.com/mongodb/mongo-go-driver/bson" |
| 9 | "github.com/mongodb/mongo-go-driver/bson/bsontype" |
| 10 | "github.com/mongodb/mongo-go-driver/x/bsonx" |
| 11 | "github.com/mongodb/mongo-go-driver/x/bsonx/bsoncore" |
| 12 | "github.com/mongodb/mongo-go-driver/x/mongo/driver/session" |
| 13 | "github.com/mongodb/mongo-go-driver/x/mongo/driver/topology" |
| 14 | "github.com/mongodb/mongo-go-driver/x/network/command" |
| 15 | "github.com/mongodb/mongo-go-driver/x/network/wiremessage" |
| 16 | ) |
| 17 | |
| 18 | // BatchCursor is a batch implementation of a cursor. It returns documents in entire batches instead |
| 19 | // of one at a time. An individual document cursor can be built on top of this batch cursor. |
| 20 | type BatchCursor struct { |
| 21 | clientSession *session.Client |
| 22 | clock *session.ClusterClock |
| 23 | namespace command.Namespace |
| 24 | id int64 |
| 25 | err error |
| 26 | server *topology.Server |
| 27 | opts []bsonx.Elem |
| 28 | currentBatch []byte |
| 29 | firstBatch bool |
| 30 | batchNumber int |
| 31 | |
| 32 | // legacy server (< 3.2) fields |
| 33 | batchSize int32 |
| 34 | limit int32 |
| 35 | numReturned int32 // number of docs returned by server |
| 36 | } |
| 37 | |
| 38 | // NewBatchCursor creates a new BatchCursor from the provided parameters. |
| 39 | func NewBatchCursor(result bsoncore.Document, clientSession *session.Client, clock *session.ClusterClock, server *topology.Server, opts ...bsonx.Elem) (*BatchCursor, error) { |
| 40 | cur, err := result.LookupErr("cursor") |
| 41 | if err != nil { |
| 42 | return nil, err |
| 43 | } |
| 44 | if cur.Type != bson.TypeEmbeddedDocument { |
| 45 | return nil, fmt.Errorf("cursor should be an embedded document but it is a BSON %s", cur.Type) |
| 46 | } |
| 47 | |
| 48 | elems, err := cur.Document().Elements() |
| 49 | if err != nil { |
| 50 | return nil, err |
| 51 | } |
| 52 | bc := &BatchCursor{ |
| 53 | clientSession: clientSession, |
| 54 | clock: clock, |
| 55 | server: server, |
| 56 | opts: opts, |
| 57 | firstBatch: true, |
| 58 | } |
| 59 | |
| 60 | var ok bool |
| 61 | for _, elem := range elems { |
| 62 | switch elem.Key() { |
| 63 | case "firstBatch": |
| 64 | arr, ok := elem.Value().ArrayOK() |
| 65 | if !ok { |
| 66 | return nil, fmt.Errorf("firstBatch should be an array but it is a BSON %s", elem.Value().Type) |
| 67 | } |
| 68 | vals, err := arr.Values() |
| 69 | if err != nil { |
| 70 | return nil, err |
| 71 | } |
| 72 | |
| 73 | for _, val := range vals { |
| 74 | if val.Type != bsontype.EmbeddedDocument { |
| 75 | return nil, fmt.Errorf("element of cursor batch is not a document, but at %s", val.Type) |
| 76 | } |
| 77 | bc.currentBatch = append(bc.currentBatch, val.Data...) |
| 78 | } |
| 79 | case "ns": |
| 80 | if elem.Value().Type != bson.TypeString { |
| 81 | return nil, fmt.Errorf("namespace should be a string but it is a BSON %s", elem.Value().Type) |
| 82 | } |
| 83 | namespace := command.ParseNamespace(elem.Value().StringValue()) |
| 84 | err = namespace.Validate() |
| 85 | if err != nil { |
| 86 | return nil, err |
| 87 | } |
| 88 | bc.namespace = namespace |
| 89 | case "id": |
| 90 | bc.id, ok = elem.Value().Int64OK() |
| 91 | if !ok { |
| 92 | return nil, fmt.Errorf("id should be an int64 but it is a BSON %s", elem.Value().Type) |
| 93 | } |
| 94 | } |
| 95 | } |
| 96 | |
| 97 | // close session if everything fits in first batch |
| 98 | if bc.id == 0 { |
| 99 | bc.closeImplicitSession() |
| 100 | } |
| 101 | return bc, nil |
| 102 | } |
| 103 | |
| 104 | // NewEmptyBatchCursor returns a batch cursor that is empty. |
| 105 | func NewEmptyBatchCursor() *BatchCursor { |
| 106 | return &BatchCursor{} |
| 107 | } |
| 108 | |
| 109 | // NewLegacyBatchCursor creates a new BatchCursor for server versions 3.0 and below from the |
| 110 | // provided parameters. |
| 111 | // |
| 112 | // TODO(GODRIVER-617): The batch parameter here should be []bsoncore.Document. Change it to this |
| 113 | // once we have the new wiremessage package that uses bsoncore instead of bson. |
| 114 | func NewLegacyBatchCursor(ns command.Namespace, cursorID int64, batch []bson.Raw, limit int32, batchSize int32, server *topology.Server) (*BatchCursor, error) { |
| 115 | bc := &BatchCursor{ |
| 116 | id: cursorID, |
| 117 | server: server, |
| 118 | namespace: ns, |
| 119 | limit: limit, |
| 120 | batchSize: batchSize, |
| 121 | numReturned: int32(len(batch)), |
| 122 | firstBatch: true, |
| 123 | } |
| 124 | |
| 125 | // take as many documents from the batch as needed |
| 126 | firstBatchSize := int32(len(batch)) |
| 127 | if limit != 0 && limit < firstBatchSize { |
| 128 | firstBatchSize = limit |
| 129 | } |
| 130 | batch = batch[:firstBatchSize] |
| 131 | for _, doc := range batch { |
| 132 | bc.currentBatch = append(bc.currentBatch, doc...) |
| 133 | } |
| 134 | |
| 135 | return bc, nil |
| 136 | } |
| 137 | |
| 138 | // ID returns the cursor ID for this batch cursor. |
| 139 | func (bc *BatchCursor) ID() int64 { |
| 140 | return bc.id |
| 141 | } |
| 142 | |
| 143 | // Next indicates if there is another batch available. Returning false does not necessarily indicate |
| 144 | // that the cursor is closed. This method will return false when an empty batch is returned. |
| 145 | // |
| 146 | // If Next returns true, there is a valid batch of documents available. If Next returns false, there |
| 147 | // is not a valid batch of documents available. |
| 148 | func (bc *BatchCursor) Next(ctx context.Context) bool { |
| 149 | if ctx == nil { |
| 150 | ctx = context.Background() |
| 151 | } |
| 152 | |
| 153 | if bc.firstBatch { |
| 154 | bc.firstBatch = false |
| 155 | return true |
| 156 | } |
| 157 | |
| 158 | if bc.id == 0 || bc.server == nil { |
| 159 | return false |
| 160 | } |
| 161 | |
| 162 | if bc.legacy() { |
| 163 | bc.legacyGetMore(ctx) |
| 164 | } else { |
| 165 | bc.getMore(ctx) |
| 166 | } |
| 167 | |
| 168 | return len(bc.currentBatch) > 0 |
| 169 | } |
| 170 | |
| 171 | // Batch will append the current batch of documents to dst. RequiredBytes can be called to determine |
| 172 | // the length of the current batch of documents. |
| 173 | // |
| 174 | // If there is no batch available, this method does nothing. |
| 175 | func (bc *BatchCursor) Batch(dst []byte) []byte { return append(dst, bc.currentBatch...) } |
| 176 | |
| 177 | // RequiredBytes returns the number of bytes required for the current batch. |
| 178 | func (bc *BatchCursor) RequiredBytes() int { return len(bc.currentBatch) } |
| 179 | |
| 180 | // Err returns the latest error encountered. |
| 181 | func (bc *BatchCursor) Err() error { return bc.err } |
| 182 | |
| 183 | // Close closes this batch cursor. |
| 184 | func (bc *BatchCursor) Close(ctx context.Context) error { |
| 185 | if ctx == nil { |
| 186 | ctx = context.Background() |
| 187 | } |
| 188 | |
| 189 | if bc.server == nil { |
| 190 | return nil |
| 191 | } |
| 192 | |
| 193 | if bc.legacy() { |
| 194 | return bc.legacyKillCursor(ctx) |
| 195 | } |
| 196 | |
| 197 | defer bc.closeImplicitSession() |
| 198 | conn, err := bc.server.Connection(ctx) |
| 199 | if err != nil { |
| 200 | return err |
| 201 | } |
| 202 | |
| 203 | _, err = (&command.KillCursors{ |
| 204 | Clock: bc.clock, |
| 205 | NS: bc.namespace, |
| 206 | IDs: []int64{bc.id}, |
| 207 | }).RoundTrip(ctx, bc.server.SelectedDescription(), conn) |
| 208 | if err != nil { |
| 209 | _ = conn.Close() // The command response error is more important here |
| 210 | return err |
| 211 | } |
| 212 | |
| 213 | bc.id = 0 |
| 214 | return conn.Close() |
| 215 | } |
| 216 | |
| 217 | func (bc *BatchCursor) closeImplicitSession() { |
| 218 | if bc.clientSession != nil && bc.clientSession.SessionType == session.Implicit { |
| 219 | bc.clientSession.EndSession() |
| 220 | } |
| 221 | } |
| 222 | |
| 223 | func (bc *BatchCursor) clearBatch() { |
| 224 | bc.currentBatch = bc.currentBatch[:0] |
| 225 | } |
| 226 | |
| 227 | func (bc *BatchCursor) getMore(ctx context.Context) { |
| 228 | bc.clearBatch() |
| 229 | if bc.id == 0 { |
| 230 | return |
| 231 | } |
| 232 | |
| 233 | conn, err := bc.server.Connection(ctx) |
| 234 | if err != nil { |
| 235 | bc.err = err |
| 236 | return |
| 237 | } |
| 238 | |
| 239 | response, err := (&command.GetMore{ |
| 240 | Clock: bc.clock, |
| 241 | ID: bc.id, |
| 242 | NS: bc.namespace, |
| 243 | Opts: bc.opts, |
| 244 | Session: bc.clientSession, |
| 245 | }).RoundTrip(ctx, bc.server.SelectedDescription(), conn) |
| 246 | if err != nil { |
| 247 | _ = conn.Close() // The command response error is more important here |
| 248 | bc.err = err |
| 249 | return |
| 250 | } |
| 251 | |
| 252 | err = conn.Close() |
| 253 | if err != nil { |
| 254 | bc.err = err |
| 255 | return |
| 256 | } |
| 257 | |
| 258 | id, err := response.LookupErr("cursor", "id") |
| 259 | if err != nil { |
| 260 | bc.err = err |
| 261 | return |
| 262 | } |
| 263 | var ok bool |
| 264 | bc.id, ok = id.Int64OK() |
| 265 | if !ok { |
| 266 | bc.err = fmt.Errorf("BSON Type %s is not %s", id.Type, bson.TypeInt64) |
| 267 | return |
| 268 | } |
| 269 | |
| 270 | // if this is the last getMore, close the session |
| 271 | if bc.id == 0 { |
| 272 | bc.closeImplicitSession() |
| 273 | } |
| 274 | |
| 275 | batch, err := response.LookupErr("cursor", "nextBatch") |
| 276 | if err != nil { |
| 277 | bc.err = err |
| 278 | return |
| 279 | } |
| 280 | var arr bson.Raw |
| 281 | arr, ok = batch.ArrayOK() |
| 282 | if !ok { |
| 283 | bc.err = fmt.Errorf("BSON Type %s is not %s", batch.Type, bson.TypeArray) |
| 284 | return |
| 285 | } |
| 286 | vals, err := arr.Values() |
| 287 | if err != nil { |
| 288 | bc.err = err |
| 289 | return |
| 290 | } |
| 291 | |
| 292 | for _, val := range vals { |
| 293 | if val.Type != bsontype.EmbeddedDocument { |
| 294 | bc.err = fmt.Errorf("element of cursor batch is not a document, but at %s", val.Type) |
| 295 | bc.currentBatch = bc.currentBatch[:0] // don't return a batch on error |
| 296 | return |
| 297 | } |
| 298 | bc.currentBatch = append(bc.currentBatch, val.Value...) |
| 299 | } |
| 300 | |
| 301 | return |
| 302 | } |
| 303 | |
| 304 | func (bc *BatchCursor) legacy() bool { |
| 305 | return bc.server.Description().WireVersion == nil || bc.server.Description().WireVersion.Max < 4 |
| 306 | } |
| 307 | |
| 308 | func (bc *BatchCursor) legacyKillCursor(ctx context.Context) error { |
| 309 | conn, err := bc.server.Connection(ctx) |
| 310 | if err != nil { |
| 311 | return err |
| 312 | } |
| 313 | |
| 314 | kc := wiremessage.KillCursors{ |
| 315 | NumberOfCursorIDs: 1, |
| 316 | CursorIDs: []int64{bc.id}, |
| 317 | CollectionName: bc.namespace.Collection, |
| 318 | DatabaseName: bc.namespace.DB, |
| 319 | } |
| 320 | |
| 321 | err = conn.WriteWireMessage(ctx, kc) |
| 322 | if err != nil { |
| 323 | _ = conn.Close() |
| 324 | return err |
| 325 | } |
| 326 | |
| 327 | err = conn.Close() // no reply from OP_KILL_CURSORS |
| 328 | if err != nil { |
| 329 | return err |
| 330 | } |
| 331 | |
| 332 | bc.id = 0 |
| 333 | bc.clearBatch() |
| 334 | return nil |
| 335 | } |
| 336 | |
| 337 | func (bc *BatchCursor) legacyGetMore(ctx context.Context) { |
| 338 | bc.clearBatch() |
| 339 | if bc.id == 0 { |
| 340 | return |
| 341 | } |
| 342 | |
| 343 | conn, err := bc.server.Connection(ctx) |
| 344 | if err != nil { |
| 345 | bc.err = err |
| 346 | return |
| 347 | } |
| 348 | |
| 349 | numToReturn := bc.batchSize |
| 350 | if bc.limit != 0 && bc.numReturned+bc.batchSize > bc.limit { |
| 351 | numToReturn = bc.limit - bc.numReturned |
| 352 | } |
| 353 | gm := wiremessage.GetMore{ |
| 354 | FullCollectionName: bc.namespace.DB + "." + bc.namespace.Collection, |
| 355 | CursorID: bc.id, |
| 356 | NumberToReturn: numToReturn, |
| 357 | } |
| 358 | |
| 359 | err = conn.WriteWireMessage(ctx, gm) |
| 360 | if err != nil { |
| 361 | _ = conn.Close() |
| 362 | bc.err = err |
| 363 | return |
| 364 | } |
| 365 | |
| 366 | response, err := conn.ReadWireMessage(ctx) |
| 367 | if err != nil { |
| 368 | _ = conn.Close() |
| 369 | bc.err = err |
| 370 | return |
| 371 | } |
| 372 | |
| 373 | err = conn.Close() |
| 374 | if err != nil { |
| 375 | bc.err = err |
| 376 | return |
| 377 | } |
| 378 | |
| 379 | reply, ok := response.(wiremessage.Reply) |
| 380 | if !ok { |
| 381 | bc.err = errors.New("did not receive OP_REPLY response") |
| 382 | return |
| 383 | } |
| 384 | |
| 385 | err = validateGetMoreReply(reply) |
| 386 | if err != nil { |
| 387 | bc.err = err |
| 388 | return |
| 389 | } |
| 390 | |
| 391 | bc.id = reply.CursorID |
| 392 | bc.numReturned += reply.NumberReturned |
| 393 | if bc.limit != 0 && bc.numReturned >= bc.limit { |
| 394 | err = bc.Close(ctx) |
| 395 | if err != nil { |
| 396 | bc.err = err |
| 397 | return |
| 398 | } |
| 399 | } |
| 400 | |
| 401 | for _, doc := range reply.Documents { |
| 402 | bc.currentBatch = append(bc.currentBatch, doc...) |
| 403 | } |
| 404 | } |
| 405 | |
| 406 | func validateGetMoreReply(reply wiremessage.Reply) error { |
| 407 | if int(reply.NumberReturned) != len(reply.Documents) { |
| 408 | return command.NewCommandResponseError("malformed OP_REPLY: NumberReturned does not match number of returned documents", nil) |
| 409 | } |
| 410 | |
| 411 | if reply.ResponseFlags&wiremessage.CursorNotFound == wiremessage.CursorNotFound { |
| 412 | return command.QueryFailureError{ |
| 413 | Message: "query failure - cursor not found", |
| 414 | } |
| 415 | } |
| 416 | if reply.ResponseFlags&wiremessage.QueryFailure == wiremessage.QueryFailure { |
| 417 | return command.QueryFailureError{ |
| 418 | Message: "query failure", |
| 419 | Response: reply.Documents[0], |
| 420 | } |
| 421 | } |
| 422 | |
| 423 | return nil |
| 424 | } |