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import { type BSONSerializeOptions, type Document, Long, pluckBSONSerializeOptions } from '../bson';
import { type OnDemandDocumentDeserializeOptions } from '../cmap/wire_protocol/on_demand/document';
import { type CursorResponse } from '../cmap/wire_protocol/responses';
import {
MongoAPIError,
MongoCursorExhaustedError,
MongoCursorInUseError,
MongoInvalidArgumentError,
MongoRuntimeError,
MongoTailableCursorError
} from '../error';
import type { MongoClient } from '../mongo_client';
import { type Abortable, TypedEventEmitter } from '../mongo_types';
import { executeOperation } from '../operations/execute_operation';
import { GetMoreOperation } from '../operations/get_more';
import { KillCursorsOperation } from '../operations/kill_cursors';
import { ReadConcern, type ReadConcernLike } from '../read_concern';
import { ReadPreference, type ReadPreferenceLike } from '../read_preference';
import { type AsyncDisposable, configureResourceManagement } from '../resource_management';
import type { Server } from '../sdam/server';
import { ClientSession, maybeClearPinnedConnection } from '../sessions';
import { type CSOTTimeoutContext, type Timeout, TimeoutContext } from '../timeout';
import {
addAbortListener,
type Disposable,
kDispose,
type MongoDBNamespace,
noop,
squashError
} from '../utils';
/**
* @internal
* TODO(NODE-2882): A cursor's getMore commands must be run on the same server it was started on
* and the same session must be used for the lifetime of the cursor. This object serves to get the
* server and session (along with the response) out of executeOperation back to the AbstractCursor.
*
* There may be a better design for communicating these values back to the cursor, currently an operation
* MUST store the selected server on itself so it can be read after executeOperation has returned.
*/
export interface InitialCursorResponse {
/** The server selected for the operation */
server: Server;
/** The session used for this operation, may be implicitly created */
session?: ClientSession;
/** The raw server response for the operation */
response: CursorResponse;
}
/** @public */
export const CURSOR_FLAGS = [
'tailable',
'oplogReplay',
'noCursorTimeout',
'awaitData',
'exhaust',
'partial'
] as const;
/** @public */
export interface CursorStreamOptions {
/** A transformation method applied to each document emitted by the stream */
transform?(this: void, doc: Document): Document;
}
/** @public */
export type CursorFlag = (typeof CURSOR_FLAGS)[number];
function removeActiveCursor(this: AbstractCursor) {
this.client.s.activeCursors.delete(this);
}
/**
* @public
* @experimental
* Specifies how `timeoutMS` is applied to the cursor. Can be either `'cursorLifeTime'` or `'iteration'`
* When set to `'iteration'`, the deadline specified by `timeoutMS` applies to each call of
* `cursor.next()`.
* When set to `'cursorLifetime'`, the deadline applies to the life of the entire cursor.
*
* Depending on the type of cursor being used, this option has different default values.
* For non-tailable cursors, this value defaults to `'cursorLifetime'`
* For tailable cursors, this value defaults to `'iteration'` since tailable cursors, by
* definition can have an arbitrarily long lifetime.
*
* @example
* ```ts
* const cursor = collection.find({}, {timeoutMS: 100, timeoutMode: 'iteration'});
* for await (const doc of cursor) {
* // process doc
* // This will throw a timeout error if any of the iterator's `next()` calls takes more than 100ms, but
* // will continue to iterate successfully otherwise, regardless of the number of batches.
* }
* ```
*
* @example
* ```ts
* const cursor = collection.find({}, { timeoutMS: 1000, timeoutMode: 'cursorLifetime' });
* const docs = await cursor.toArray(); // This entire line will throw a timeout error if all batches are not fetched and returned within 1000ms.
* ```
*/
export const CursorTimeoutMode = Object.freeze({
ITERATION: 'iteration',
LIFETIME: 'cursorLifetime'
} as const);
/**
* @public
* @experimental
*/
export type CursorTimeoutMode = (typeof CursorTimeoutMode)[keyof typeof CursorTimeoutMode];
/** @public */
export interface AbstractCursorOptions extends BSONSerializeOptions {
session?: ClientSession;
readPreference?: ReadPreferenceLike;
readConcern?: ReadConcernLike;
/**
* Specifies the number of documents to return in each response from MongoDB
*/
batchSize?: number;
/**
* When applicable `maxTimeMS` controls the amount of time the initial command
* that constructs a cursor should take. (ex. find, aggregate, listCollections)
*/
maxTimeMS?: number;
/**
* When applicable `maxAwaitTimeMS` controls the amount of time subsequent getMores
* that a cursor uses to fetch more data should take. (ex. cursor.next())
*/
maxAwaitTimeMS?: number;
/**
* Comment to apply to the operation.
*
* In server versions pre-4.4, 'comment' must be string. A server
* error will be thrown if any other type is provided.
*
* In server versions 4.4 and above, 'comment' can be any valid BSON type.
*/
comment?: unknown;
/**
* By default, MongoDB will automatically close a cursor when the
* client has exhausted all results in the cursor. However, for [capped collections](https://www.mongodb.com/docs/manual/core/capped-collections)
* you may use a Tailable Cursor that remains open after the client exhausts
* the results in the initial cursor.
*/
tailable?: boolean;
/**
* If awaitData is set to true, when the cursor reaches the end of the capped collection,
* MongoDB blocks the query thread for a period of time waiting for new data to arrive.
* When new data is inserted into the capped collection, the blocked thread is signaled
* to wake up and return the next batch to the client.
*/
awaitData?: boolean;
noCursorTimeout?: boolean;
/** Specifies the time an operation will run until it throws a timeout error. See {@link AbstractCursorOptions.timeoutMode} for more details on how this option applies to cursors. */
timeoutMS?: number;
/**
* @public
* @experimental
* Specifies how `timeoutMS` is applied to the cursor. Can be either `'cursorLifeTime'` or `'iteration'`
* When set to `'iteration'`, the deadline specified by `timeoutMS` applies to each call of
* `cursor.next()`.
* When set to `'cursorLifetime'`, the deadline applies to the life of the entire cursor.
*
* Depending on the type of cursor being used, this option has different default values.
* For non-tailable cursors, this value defaults to `'cursorLifetime'`
* For tailable cursors, this value defaults to `'iteration'` since tailable cursors, by
* definition can have an arbitrarily long lifetime.
*
* @example
* ```ts
* const cursor = collection.find({}, {timeoutMS: 100, timeoutMode: 'iteration'});
* for await (const doc of cursor) {
* // process doc
* // This will throw a timeout error if any of the iterator's `next()` calls takes more than 100ms, but
* // will continue to iterate successfully otherwise, regardless of the number of batches.
* }
* ```
*
* @example
* ```ts
* const cursor = collection.find({}, { timeoutMS: 1000, timeoutMode: 'cursorLifetime' });
* const docs = await cursor.toArray(); // This entire line will throw a timeout error if all batches are not fetched and returned within 1000ms.
* ```
*/
timeoutMode?: CursorTimeoutMode;
/**
* @internal
*
* A timeout context to govern the total time the cursor can live. If provided, the cursor
* cannot be used in ITERATION mode.
*/
timeoutContext?: CursorTimeoutContext;
}
/** @internal */
export type InternalAbstractCursorOptions = Omit<AbstractCursorOptions, 'readPreference'> & {
// resolved
readPreference: ReadPreference;
readConcern?: ReadConcern;
// cursor flags, some are deprecated
oplogReplay?: boolean;
exhaust?: boolean;
partial?: boolean;
omitMaxTimeMS?: boolean;
};
/** @public */
export type AbstractCursorEvents = {
[AbstractCursor.CLOSE](): void;
};
/** @public */
export abstract class AbstractCursor<
TSchema = any,
CursorEvents extends AbstractCursorEvents = AbstractCursorEvents
>
extends TypedEventEmitter<CursorEvents>
implements AsyncDisposable
{
/** @internal */
private cursorId: Long | null;
/** @internal */
private cursorSession: ClientSession;
/** @internal */
private selectedServer?: Server;
/** @internal */
private cursorNamespace: MongoDBNamespace;
/** @internal */
private documents: CursorResponse | null = null;
/** @internal */
private cursorClient: MongoClient;
/** @internal */
private transform?: (doc: TSchema) => any;
/**
* @internal
* This is true whether or not the first command fails. It only indicates whether or not the first
* command has been run.
*/
private initialized: boolean;
/** @internal */
private isClosed: boolean;
/** @internal */
private isKilled: boolean;
/** @internal */
protected readonly cursorOptions: InternalAbstractCursorOptions;
/** @internal */
protected timeoutContext?: CursorTimeoutContext;
/** @event */
static readonly CLOSE = 'close' as const;
/** @internal */
protected deserializationOptions: OnDemandDocumentDeserializeOptions;
protected signal: AbortSignal | undefined;
private abortListener: Disposable | undefined;
/** @internal */
protected constructor(
client: MongoClient,
namespace: MongoDBNamespace,
options: AbstractCursorOptions & Abortable = {}
) {
super();
this.on('error', noop);
Iif (!client.s.isMongoClient) {
throw new MongoRuntimeError('Cursor must be constructed with MongoClient');
}
this.cursorClient = client;
this.cursorNamespace = namespace;
this.cursorId = null;
this.initialized = false;
this.isClosed = false;
this.isKilled = false;
this.cursorOptions = {
readPreference:
options.readPreference && options.readPreference instanceof ReadPreference
? options.readPreference
: ReadPreference.primary,
...pluckBSONSerializeOptions(options),
timeoutMS: options?.timeoutContext?.csotEnabled()
? options.timeoutContext.timeoutMS
: options.timeoutMS,
tailable: options.tailable,
awaitData: options.awaitData
};
if (this.cursorOptions.timeoutMS != null) {
if (options.timeoutMode == null) {
if (options.tailable) {
if (options.awaitData) {
if (
options.maxAwaitTimeMS != null &&
options.maxAwaitTimeMS >= this.cursorOptions.timeoutMS
)
throw new MongoInvalidArgumentError(
'Cannot specify maxAwaitTimeMS >= timeoutMS for a tailable awaitData cursor'
);
}
this.cursorOptions.timeoutMode = CursorTimeoutMode.ITERATION;
} else {
this.cursorOptions.timeoutMode = CursorTimeoutMode.LIFETIME;
}
} else {
if (options.tailable && options.timeoutMode === CursorTimeoutMode.LIFETIME) {
throw new MongoInvalidArgumentError(
"Cannot set tailable cursor's timeoutMode to LIFETIME"
);
}
this.cursorOptions.timeoutMode = options.timeoutMode;
}
} else {
if (options.timeoutMode != null)
throw new MongoInvalidArgumentError('Cannot set timeoutMode without setting timeoutMS');
}
// Set for initial command
this.cursorOptions.omitMaxTimeMS =
this.cursorOptions.timeoutMS != null &&
((this.cursorOptions.timeoutMode === CursorTimeoutMode.ITERATION &&
!this.cursorOptions.tailable) ||
(this.cursorOptions.tailable && !this.cursorOptions.awaitData));
const readConcern = ReadConcern.fromOptions(options);
if (readConcern) {
this.cursorOptions.readConcern = readConcern;
}
if (typeof options.batchSize === 'number') {
this.cursorOptions.batchSize = options.batchSize;
}
// we check for undefined specifically here to allow falsy values
// eslint-disable-next-line no-restricted-syntax
if (options.comment !== undefined) {
this.cursorOptions.comment = options.comment;
}
if (typeof options.maxTimeMS === 'number') {
this.cursorOptions.maxTimeMS = options.maxTimeMS;
}
if (typeof options.maxAwaitTimeMS === 'number') {
this.cursorOptions.maxAwaitTimeMS = options.maxAwaitTimeMS;
}
if (options.session instanceof ClientSession) {
this.cursorSession = options.session;
} else {
this.cursorSession = this.cursorClient.startSession({ owner: this, explicit: false });
}
this.deserializationOptions = {
...this.cursorOptions,
validation: {
utf8: options?.enableUtf8Validation === false ? false : true
}
};
this.timeoutContext = options.timeoutContext;
this.signal = options.signal;
this.abortListener = addAbortListener(
this.signal,
() => void this.close().then(undefined, squashError)
);
this.trackCursor();
}
/**
* The cursor has no id until it receives a response from the initial cursor creating command.
*
* It is non-zero for as long as the database has an open cursor.
*
* The initiating command may receive a zero id if the entire result is in the `firstBatch`.
*/
get id(): Long | undefined {
return this.cursorId ?? undefined;
}
/** @internal */
get isDead() {
return (this.cursorId?.isZero() ?? false) || this.isClosed || this.isKilled;
}
/** @internal */
get client(): MongoClient {
return this.cursorClient;
}
/** @internal */
get server(): Server | undefined {
return this.selectedServer;
}
get namespace(): MongoDBNamespace {
return this.cursorNamespace;
}
get readPreference(): ReadPreference {
return this.cursorOptions.readPreference;
}
get readConcern(): ReadConcern | undefined {
return this.cursorOptions.readConcern;
}
/** @internal */
get session(): ClientSession {
return this.cursorSession;
}
set session(clientSession: ClientSession) {
this.cursorSession = clientSession;
}
/**
* The cursor is closed and all remaining locally buffered documents have been iterated.
*/
get closed(): boolean {
return this.isClosed && (this.documents?.length ?? 0) === 0;
}
/**
* A `killCursors` command was attempted on this cursor.
* This is performed if the cursor id is non zero.
*/
get killed(): boolean {
return this.isKilled;
}
get loadBalanced(): boolean {
return !!this.cursorClient.topology?.loadBalanced;
}
/**
* @beta
* @experimental
* An alias for {@link AbstractCursor.close|AbstractCursor.close()}.
*/
declare [Symbol.asyncDispose]: () => Promise<void>;
/** @internal */
async asyncDispose() {
await this.close();
}
/** Adds cursor to client's tracking so it will be closed by MongoClient.close() */
private trackCursor() {
this.cursorClient.s.activeCursors.add(this);
if (!this.listeners('close').includes(removeActiveCursor)) {
this.once('close', removeActiveCursor);
}
}
/** Returns current buffered documents length */
bufferedCount(): number {
return this.documents?.length ?? 0;
}
/** Returns current buffered documents */
readBufferedDocuments(number?: number): NonNullable<TSchema>[] {
const bufferedDocs: NonNullable<TSchema>[] = [];
const documentsToRead = Math.min(
number ?? this.documents?.length ?? 0,
this.documents?.length ?? 0
);
for (let count = 0; count < documentsToRead; count++) {
const document = this.documents?.shift(this.deserializationOptions);
Eif (document != null) {
bufferedDocs.push(document);
}
}
return bufferedDocs;
}
async *[Symbol.asyncIterator](): AsyncGenerator<TSchema, void, void> {
this.signal?.throwIfAborted();
if (this.closed) {
return;
}
try {
while (true) {
if (this.isKilled) {
return;
}
if (this.closed) {
return;
}
Iif (this.cursorId != null && this.isDead && (this.documents?.length ?? 0) === 0) {
return;
}
const document = await this.next();
// eslint-disable-next-line no-restricted-syntax
if (document === null) {
return;
}
yield document;
this.signal?.throwIfAborted();
}
} finally {
// Only close the cursor if it has not already been closed. This finally clause handles
// the case when a user would break out of a for await of loop early.
if (!this.isClosed) {
try {
await this.close();
} catch (error) {
squashError(error);
}
}
}
}
stream(options?: CursorStreamOptions): Readable & AsyncIterable<TSchema> {
const readable = new ReadableCursorStream(this);
const abortListener = addAbortListener(this.signal, function () {
readable.destroy(this.reason);
});
readable.once('end', () => {
abortListener?.[kDispose]();
});
if (options?.transform) {
const transform = options.transform;
const transformedStream = readable.pipe(
new Transform({
objectMode: true,
highWaterMark: 1,
transform(chunk, _, callback) {
try {
const transformed = transform(chunk);
callback(undefined, transformed);
} catch (err) {
callback(err);
}
}
})
);
// Bubble errors to transformed stream, because otherwise no way
// to handle this error.
readable.on('error', err => transformedStream.emit('error', err));
return transformedStream;
}
return readable;
}
async hasNext(): Promise<boolean> {
this.signal?.throwIfAborted();
Iif (this.cursorId === Long.ZERO) {
return false;
}
Iif (this.cursorOptions.timeoutMode === CursorTimeoutMode.ITERATION && this.cursorId != null) {
this.timeoutContext?.refresh();
}
try {
do {
if ((this.documents?.length ?? 0) !== 0) {
return true;
}
await this.fetchBatch();
} while (!this.isDead || (this.documents?.length ?? 0) !== 0);
} finally {
if (this.cursorOptions.timeoutMode === CursorTimeoutMode.ITERATION) {
this.timeoutContext?.clear();
}
}
return false;
}
/** Get the next available document from the cursor, returns null if no more documents are available. */
async next(): Promise<TSchema | null> {
this.signal?.throwIfAborted();
if (this.cursorId === Long.ZERO) {
throw new MongoCursorExhaustedError();
}
if (this.cursorOptions.timeoutMode === CursorTimeoutMode.ITERATION && this.cursorId != null) {
this.timeoutContext?.refresh();
}
try {
do {
const doc = this.documents?.shift(this.deserializationOptions);
if (doc != null) {
if (this.transform != null) return await this.transformDocument(doc);
return doc;
}
await this.fetchBatch();
} while (!this.isDead || (this.documents?.length ?? 0) !== 0);
} finally {
if (this.cursorOptions.timeoutMode === CursorTimeoutMode.ITERATION) {
this.timeoutContext?.clear();
}
}
return null;
}
/**
* Try to get the next available document from the cursor or `null` if an empty batch is returned
*/
async tryNext(): Promise<TSchema | null> {
this.signal?.throwIfAborted();
Iif (this.cursorId === Long.ZERO) {
throw new MongoCursorExhaustedError();
}
if (this.cursorOptions.timeoutMode === CursorTimeoutMode.ITERATION && this.cursorId != null) {
this.timeoutContext?.refresh();
}
try {
let doc = this.documents?.shift(this.deserializationOptions);
if (doc != null) {
Iif (this.transform != null) return await this.transformDocument(doc);
return doc;
}
await this.fetchBatch();
doc = this.documents?.shift(this.deserializationOptions);
if (doc != null) {
if (this.transform != null) return await this.transformDocument(doc);
return doc;
}
} finally {
if (this.cursorOptions.timeoutMode === CursorTimeoutMode.ITERATION) {
this.timeoutContext?.clear();
}
}
return null;
}
/**
* Iterates over all the documents for this cursor using the iterator, callback pattern.
*
* If the iterator returns `false`, iteration will stop.
*
* @param iterator - The iteration callback.
* @deprecated - Will be removed in a future release. Use for await...of instead.
*/
async forEach(iterator: (doc: TSchema) => boolean | void): Promise<void> {
this.signal?.throwIfAborted();
Iif (typeof iterator !== 'function') {
throw new MongoInvalidArgumentError('Argument "iterator" must be a function');
}
for await (const document of this) {
const result = iterator(document);
if (result === false) {
break;
}
}
}
/**
* Frees any client-side resources used by the cursor.
*/
async close(options?: { timeoutMS?: number }): Promise<void> {
await this.cleanup(options?.timeoutMS);
}
/**
* Returns an array of documents. The caller is responsible for making sure that there
* is enough memory to store the results. Note that the array only contains partial
* results when this cursor had been previously accessed. In that case,
* cursor.rewind() can be used to reset the cursor.
*/
async toArray(): Promise<TSchema[]> {
this.signal?.throwIfAborted();
const array: TSchema[] = [];
// at the end of the loop (since readBufferedDocuments is called) the buffer will be empty
// then, the 'await of' syntax will run a getMore call
for await (const document of this) {
array.push(document);
const docs = this.readBufferedDocuments();
if (this.transform != null) {
for (const doc of docs) {
array.push(await this.transformDocument(doc));
}
} else {
array.push(...docs);
}
}
return array;
}
/**
* Add a cursor flag to the cursor
*
* @param flag - The flag to set, must be one of following ['tailable', 'oplogReplay', 'noCursorTimeout', 'awaitData', 'partial' -.
* @param value - The flag boolean value.
*/
addCursorFlag(flag: CursorFlag, value: boolean): this {
this.throwIfInitialized();
Iif (!CURSOR_FLAGS.includes(flag)) {
throw new MongoInvalidArgumentError(`Flag ${flag} is not one of ${CURSOR_FLAGS}`);
}
Iif (typeof value !== 'boolean') {
throw new MongoInvalidArgumentError(`Flag ${flag} must be a boolean value`);
}
this.cursorOptions[flag] = value;
return this;
}
/**
* Map all documents using the provided function
* If there is a transform set on the cursor, that will be called first and the result passed to
* this function's transform.
*
* @remarks
*
* **Note** Cursors use `null` internally to indicate that there are no more documents in the cursor. Providing a mapping
* function that maps values to `null` will result in the cursor closing itself before it has finished iterating
* all documents. This will **not** result in a memory leak, just surprising behavior. For example:
*
* ```typescript
* const cursor = collection.find({});
* cursor.map(() => null);
*
* const documents = await cursor.toArray();
* // documents is always [], regardless of how many documents are in the collection.
* ```
*
* Other falsey values are allowed:
*
* ```typescript
* const cursor = collection.find({});
* cursor.map(() => '');
*
* const documents = await cursor.toArray();
* // documents is now an array of empty strings
* ```
*
* **Note for Typescript Users:** adding a transform changes the return type of the iteration of this cursor,
* it **does not** return a new instance of a cursor. This means when calling map,
* you should always assign the result to a new variable in order to get a correctly typed cursor variable.
* Take note of the following example:
*
* @example
* ```typescript
* const cursor: FindCursor<Document> = coll.find();
* const mappedCursor: FindCursor<number> = cursor.map(doc => Object.keys(doc).length);
* const keyCounts: number[] = await mappedCursor.toArray(); // cursor.toArray() still returns Document[]
* ```
* @param transform - The mapping transformation method.
*/
map<T = any>(transform: (doc: TSchema) => T): AbstractCursor<T> {
this.throwIfInitialized();
const oldTransform = this.transform;
if (oldTransform) {
this.transform = doc => {
return transform(oldTransform(doc));
};
} else {
this.transform = transform;
}
return this as unknown as AbstractCursor<T>;
}
/**
* Set the ReadPreference for the cursor.
*
* @param readPreference - The new read preference for the cursor.
*/
withReadPreference(readPreference: ReadPreferenceLike): this {
this.throwIfInitialized();
if (readPreference instanceof ReadPreference) {
this.cursorOptions.readPreference = readPreference;
} else Eif (typeof readPreference === 'string') {
this.cursorOptions.readPreference = ReadPreference.fromString(readPreference);
} else {
throw new MongoInvalidArgumentError(`Invalid read preference: ${readPreference}`);
}
return this;
}
/**
* Set the ReadPreference for the cursor.
*
* @param readPreference - The new read preference for the cursor.
*/
withReadConcern(readConcern: ReadConcernLike): this {
this.throwIfInitialized();
const resolvedReadConcern = ReadConcern.fromOptions({ readConcern });
Eif (resolvedReadConcern) {
this.cursorOptions.readConcern = resolvedReadConcern;
}
return this;
}
/**
* Set a maxTimeMS on the cursor query, allowing for hard timeout limits on queries (Only supported on MongoDB 2.6 or higher)
*
* @param value - Number of milliseconds to wait before aborting the query.
*/
maxTimeMS(value: number): this {
this.throwIfInitialized();
Iif (typeof value !== 'number') {
throw new MongoInvalidArgumentError('Argument for maxTimeMS must be a number');
}
this.cursorOptions.maxTimeMS = value;
return this;
}
/**
* Set the batch size for the cursor.
*
* @param value - The number of documents to return per batch. See {@link https://www.mongodb.com/docs/manual/reference/command/find/|find command documentation}.
*/
batchSize(value: number): this {
this.throwIfInitialized();
Iif (this.cursorOptions.tailable) {
throw new MongoTailableCursorError('Tailable cursor does not support batchSize');
}
if (typeof value !== 'number') {
throw new MongoInvalidArgumentError('Operation "batchSize" requires an integer');
}
this.cursorOptions.batchSize = value;
return this;
}
/**
* Rewind this cursor to its uninitialized state. Any options that are present on the cursor will
* remain in effect. Iterating this cursor will cause new queries to be sent to the server, even
* if the resultant data has already been retrieved by this cursor.
*/
rewind(): void {
if (this.timeoutContext && this.timeoutContext.owner !== this) {
throw new MongoAPIError(`Cannot rewind cursor that does not own its timeout context.`);
}
if (!this.initialized) {
return;
}
this.cursorId = null;
this.documents?.clear();
this.timeoutContext?.clear();
this.timeoutContext = undefined;
this.isClosed = false;
this.isKilled = false;
this.initialized = false;
this.hasEmittedClose = false;
this.trackCursor();
// We only want to end this session if we created it, and it hasn't ended yet
if (this.cursorSession.explicit === false) {
if (!this.cursorSession.hasEnded) {
this.cursorSession.endSession().then(undefined, squashError);
}
this.cursorSession = this.cursorClient.startSession({ owner: this, explicit: false });
}
}
/**
* Returns a new uninitialized copy of this cursor, with options matching those that have been set on the current instance
*/
abstract clone(): AbstractCursor<TSchema>;
/** @internal */
protected abstract _initialize(
session: ClientSession | undefined
): Promise<InitialCursorResponse>;
/** @internal */
async getMore(batchSize: number): Promise<CursorResponse> {
Iif (this.cursorId == null) {
throw new MongoRuntimeError(
'Unexpected null cursor id. A cursor creating command should have set this'
);
}
Iif (this.selectedServer == null) {
throw new MongoRuntimeError(
'Unexpected null selectedServer. A cursor creating command should have set this'
);
}
const getMoreOptions = {
...this.cursorOptions,
session: this.cursorSession,
batchSize
};
const getMoreOperation = new GetMoreOperation(
this.cursorNamespace,
this.cursorId,
this.selectedServer,
getMoreOptions
);
return await executeOperation(this.cursorClient, getMoreOperation, this.timeoutContext);
}
/**
* @internal
*
* This function is exposed for the unified test runner's createChangeStream
* operation. We cannot refactor to use the abstract _initialize method without
* a significant refactor.
*/
private async cursorInit(): Promise<void> {
if (this.cursorOptions.timeoutMS != null) {
this.timeoutContext ??= new CursorTimeoutContext(
TimeoutContext.create({
serverSelectionTimeoutMS: this.client.s.options.serverSelectionTimeoutMS,
timeoutMS: this.cursorOptions.timeoutMS
}),
this
);
}
try {
const state = await this._initialize(this.cursorSession);
// Set omitMaxTimeMS to the value needed for subsequent getMore calls
this.cursorOptions.omitMaxTimeMS = this.cursorOptions.timeoutMS != null;
const response = state.response;
this.selectedServer = state.server;
this.cursorId = response.id;
this.cursorNamespace = response.ns ?? this.namespace;
this.documents = response;
this.initialized = true; // the cursor is now initialized, even if it is dead
} catch (error) {
// the cursor is now initialized, even if an error occurred
this.initialized = true;
await this.cleanup(undefined, error);
throw error;
}
if (this.isDead) {
await this.cleanup();
}
return;
}
/** @internal Attempt to obtain more documents */
private async fetchBatch(): Promise<void> {
if (this.isClosed) {
return;
}
Iif (this.isDead) {
// if the cursor is dead, we clean it up
// cleanupCursor should never throw, but if it does it indicates a bug in the driver
// and we should surface the error
await this.cleanup();
return;
}
if (this.cursorId == null) {
await this.cursorInit();
// If the cursor died or returned documents, return
if ((this.documents?.length ?? 0) !== 0 || this.isDead) return;
// Otherwise, run a getMore
}
// otherwise need to call getMore
const batchSize = this.cursorOptions.batchSize || 1000;
try {
const response = await this.getMore(batchSize);
this.cursorId = response.id;
this.documents = response;
} catch (error) {
try {
await this.cleanup(undefined, error);
} catch (cleanupError) {
// `cleanupCursor` should never throw, squash and throw the original error
squashError(cleanupError);
}
throw error;
}
if (this.isDead) {
// If we successfully received a response from a cursor BUT the cursor indicates that it is exhausted,
// we intentionally clean up the cursor to release its session back into the pool before the cursor
// is iterated. This prevents a cursor that is exhausted on the server from holding
// onto a session indefinitely until the AbstractCursor is iterated.
//
// cleanupCursorAsync should never throw, but if it does it indicates a bug in the driver
// and we should surface the error
await this.cleanup();
}
}
/** @internal */
private async cleanup(timeoutMS?: number, error?: Error) {
this.abortListener?.[kDispose]();
this.isClosed = true;
const timeoutContextForKillCursors = (): CursorTimeoutContext | undefined => {
if (timeoutMS != null) {
this.timeoutContext?.clear();
return new CursorTimeoutContext(
TimeoutContext.create({
serverSelectionTimeoutMS: this.client.s.options.serverSelectionTimeoutMS,
timeoutMS
}),
this
);
} else {
return this.timeoutContext?.refreshed();
}
};
try {
if (
!this.isKilled &&
this.cursorId &&
!this.cursorId.isZero() &&
this.cursorNamespace &&
this.selectedServer &&
!this.cursorSession.hasEnded
) {
this.isKilled = true;
const cursorId = this.cursorId;
this.cursorId = Long.ZERO;
await executeOperation(
this.cursorClient,
new KillCursorsOperation(cursorId, this.cursorNamespace, this.selectedServer, {
session: this.cursorSession
}),
timeoutContextForKillCursors()
);
}
} catch (error) {
squashError(error);
} finally {
try {
if (this.cursorSession?.owner === this) {
await this.cursorSession.endSession({ error });
}
if (!this.cursorSession?.inTransaction()) {
maybeClearPinnedConnection(this.cursorSession, { error });
}
} finally {
this.emitClose();
}
}
}
/** @internal */
private hasEmittedClose = false;
/** @internal */
private emitClose() {
try {
if (!this.hasEmittedClose && ((this.documents?.length ?? 0) === 0 || this.isClosed)) {
// @ts-expect-error: CursorEvents is generic so Parameters<CursorEvents["close"]> may not be assignable to `[]`. Not sure how to require extenders do not add parameters.
this.emit('close');
}
} finally {
this.hasEmittedClose = true;
}
}
/** @internal */
private async transformDocument(document: NonNullable<TSchema>): Promise<NonNullable<TSchema>> {
Iif (this.transform == null) return document;
try {
const transformedDocument = this.transform(document);
// eslint-disable-next-line no-restricted-syntax
if (transformedDocument === null) {
const TRANSFORM_TO_NULL_ERROR =
'Cursor returned a `null` document, but the cursor is not exhausted. Mapping documents to `null` is not supported in the cursor transform.';
throw new MongoAPIError(TRANSFORM_TO_NULL_ERROR);
}
return transformedDocument;
} catch (transformError) {
try {
await this.close();
} catch (closeError) {
squashError(closeError);
}
throw transformError;
}
}
/** @internal */
protected throwIfInitialized() {
if (this.initialized) throw new MongoCursorInUseError();
}
}
class ReadableCursorStream extends Readable {
private _cursor: AbstractCursor;
private _readInProgress = false;
constructor(cursor: AbstractCursor) {
super({
objectMode: true,
autoDestroy: false,
highWaterMark: 1
});
this._cursor = cursor;
}
// eslint-disable-next-line @typescript-eslint/no-unused-vars
override _read(size: number): void {
if (!this._readInProgress) {
this._readInProgress = true;
this._readNext();
}
}
override _destroy(error: Error | null, callback: (error?: Error | null) => void): void {
this._cursor.close().then(
() => callback(error),
closeError => callback(closeError)
);
}
private _readNext() {
if (this._cursor.id === Long.ZERO) {
this.push(null);
return;
}
this._cursor
.next()
.then(
// result from next()
result => {
if (result == null) {
this.push(null);
} else if (this.destroyed) {
this._cursor.close().then(undefined, squashError);
} else {
if (this.push(result)) {
return this._readNext();
}
this._readInProgress = false;
}
},
// error from next()
err => {
// NOTE: This is questionable, but we have a test backing the behavior. It seems the
// desired behavior is that a stream ends cleanly when a user explicitly closes
// a client during iteration. Alternatively, we could do the "right" thing and
// propagate the error message by removing this special case.
Iif (err.message.match(/server is closed/)) {
this._cursor.close().then(undefined, squashError);
return this.push(null);
}
// NOTE: This is also perhaps questionable. The rationale here is that these errors tend
// to be "operation was interrupted", where a cursor has been closed but there is an
// active getMore in-flight. This used to check if the cursor was killed but once
// that changed to happen in cleanup legitimate errors would not destroy the
// stream. There are change streams test specifically test these cases.
if (err.message.match(/operation was interrupted/)) {
return this.push(null);
}
// NOTE: The two above checks on the message of the error will cause a null to be pushed
// to the stream, thus closing the stream before the destroy call happens. This means
// that either of those error messages on a change stream will not get a proper
// 'error' event to be emitted (the error passed to destroy). Change stream resumability
// relies on that error event to be emitted to create its new cursor and thus was not
// working on 4.4 servers because the error emitted on failover was "interrupted at
// shutdown" while on 5.0+ it is "The server is in quiesce mode and will shut down".
// See NODE-4475.
return this.destroy(err);
}
)
// if either of the above handlers throw
.catch(error => {
this._readInProgress = false;
this.destroy(error);
});
}
}
configureResourceManagement(AbstractCursor.prototype);
/**
* @internal
* The cursor timeout context is a wrapper around a timeout context
* that keeps track of the "owner" of the cursor. For timeout contexts
* instantiated inside a cursor, the owner will be the cursor.
*
* All timeout behavior is exactly the same as the wrapped timeout context's.
*/
export class CursorTimeoutContext extends TimeoutContext {
constructor(
public timeoutContext: TimeoutContext,
public owner: symbol | AbstractCursor
) {
super();
}
override get serverSelectionTimeout(): Timeout | null {
return this.timeoutContext.serverSelectionTimeout;
}
override get connectionCheckoutTimeout(): Timeout | null {
return this.timeoutContext.connectionCheckoutTimeout;
}
override get clearServerSelectionTimeout(): boolean {
return this.timeoutContext.clearServerSelectionTimeout;
}
override get timeoutForSocketWrite(): Timeout | null {
return this.timeoutContext.timeoutForSocketWrite;
}
override get timeoutForSocketRead(): Timeout | null {
return this.timeoutContext.timeoutForSocketRead;
}
override csotEnabled(): this is CSOTTimeoutContext {
return this.timeoutContext.csotEnabled();
}
override refresh(): void {
if (typeof this.owner !== 'symbol') return this.timeoutContext.refresh();
}
override clear(): void {
if (typeof this.owner !== 'symbol') return this.timeoutContext.clear();
}
override get maxTimeMS(): number | null {
return this.timeoutContext.maxTimeMS;
}
get timeoutMS(): number | null {
return this.timeoutContext.csotEnabled() ? this.timeoutContext.timeoutMS : null;
}
override refreshed(): CursorTimeoutContext {
return new CursorTimeoutContext(this.timeoutContext.refreshed(), this.owner);
}
override addMaxTimeMSToCommand(command: Document, options: { omitMaxTimeMS?: boolean }): void {
this.timeoutContext.addMaxTimeMSToCommand(command, options);
}
override getSocketTimeoutMS(): number | undefined {
return this.timeoutContext.getSocketTimeoutMS();
}
}
|