feat(NODE-6090): Implement CSOT logic for connection checkout and server selection

Author: W-A-James

src/admin.ts

@@ -78,7 +78,8 @@ export class Admin {
       new RunAdminCommandOperation(command, {
         ...resolveBSONOptions(options),
         session: options?.session,
-        readPreference: options?.readPreference
+        readPreference: options?.readPreference,
+        timeoutMS: options?.timeoutMS ?? this.s.db.timeoutMS
       })
     );
   }

src/cmap/connection.ts

@@ -29,6 +29,7 @@ import { type CancellationToken, TypedEventEmitter } from '../mongo_types';
 import { ReadPreference, type ReadPreferenceLike } from '../read_preference';
 import { ServerType } from '../sdam/common';
 import { applySession, type ClientSession, updateSessionFromResponse } from '../sessions';
+import { type Timeout } from '../timeout';
 import {
   BufferPool,
   calculateDurationInMs,
@@ -93,6 +94,9 @@ export interface CommandOptions extends BSONSerializeOptions {
   writeConcern?: WriteConcern;
 
   directConnection?: boolean;
+
+  /** @internal */
+  timeout?: Timeout;
 }
 
 /** @public */

src/cmap/connection_pool.ts

@@ -21,13 +21,14 @@ import {
   MongoInvalidArgumentError,
   MongoMissingCredentialsError,
   MongoNetworkError,
+  MongoOperationTimeoutError,
   MongoRuntimeError,
   MongoServerError
 } from '../error';
 import { CancellationToken, TypedEventEmitter } from '../mongo_types';
 import type { Server } from '../sdam/server';
 import { Timeout, TimeoutError } from '../timeout';
-import { type Callback, List, makeCounter, promiseWithResolvers } from '../utils';
+import { type Callback, csotMin, List, makeCounter, promiseWithResolvers } from '../utils';
 import { connect } from './connect';
 import { Connection, type ConnectionEvents, type ConnectionOptions } from './connection';
 import {
@@ -102,7 +103,6 @@ export interface ConnectionPoolOptions extends Omit<ConnectionOptions, 'id' | 'g
 export interface WaitQueueMember {
   resolve: (conn: Connection) => void;
   reject: (err: AnyError) => void;
-  timeout: Timeout;
   [kCancelled]?: boolean;
 }
 
@@ -354,35 +354,57 @@ export class ConnectionPool extends TypedEventEmitter<ConnectionPoolEvents> {
    * will be held by the pool. This means that if a connection is checked out it MUST be checked back in or
    * explicitly destroyed by the new owner.
    */
-  async checkOut(): Promise<Connection> {
+  async checkOut(options?: { timeout?: Timeout }): Promise<Connection> {
     this.emitAndLog(
       ConnectionPool.CONNECTION_CHECK_OUT_STARTED,
       new ConnectionCheckOutStartedEvent(this)
     );
 
     const waitQueueTimeoutMS = this.options.waitQueueTimeoutMS;
+    const serverSelectionTimeoutMS = this[kServer].topology.s.serverSelectionTimeoutMS;
 
     const { promise, resolve, reject } = promiseWithResolvers<Connection>();
 
-    const timeout = Timeout.expires(waitQueueTimeoutMS);
+    let timeout: Timeout | null = null;
+    if (options?.timeout) {
+      // CSOT enabled
+      // Determine if we're using the timeout passed in or a new timeout
+      if (options.timeout.duration > 0 || serverSelectionTimeoutMS > 0) {
+        // This check determines whether or not Topology.selectServer used the configured
+        // `timeoutMS` or `serverSelectionTimeoutMS` value for its timeout
+        if (
+          options.timeout.duration === serverSelectionTimeoutMS ||
+          csotMin(options.timeout.duration, serverSelectionTimeoutMS) < serverSelectionTimeoutMS
+        ) {
+          // server selection used `timeoutMS`, so we should use the existing timeout as the timeout
+          // here
+          timeout = options.timeout;
+        } else {
+          // server selection used `serverSelectionTimeoutMS`, so we construct a new timeout with
+          // the time remaining to ensure that Topology.selectServer and ConnectionPool.checkOut
+          // cumulatively don't spend more than `serverSelectionTimeoutMS` blocking
+          timeout = Timeout.expires(serverSelectionTimeoutMS - options.timeout.timeElapsed);
+        }
+      }
+    } else {
+      timeout = Timeout.expires(waitQueueTimeoutMS);
+    }
 
     const waitQueueMember: WaitQueueMember = {
       resolve,
-      reject,
-      timeout
+      reject
     };
 
     this[kWaitQueue].push(waitQueueMember);
     process.nextTick(() => this.processWaitQueue());
 
     try {
-      return await Promise.race([promise, waitQueueMember.timeout]);
+      timeout?.throwIfExpired();
+      return await (timeout ? Promise.race([promise, timeout]) : promise);
     } catch (error) {
       if (TimeoutError.is(error)) {
         waitQueueMember[kCancelled] = true;
 
-        waitQueueMember.timeout.clear();
-
         this.emitAndLog(
           ConnectionPool.CONNECTION_CHECK_OUT_FAILED,
           new ConnectionCheckOutFailedEvent(this, 'timeout')
@@ -393,9 +415,16 @@ export class ConnectionPool extends TypedEventEmitter<ConnectionPoolEvents> {
             : 'Timed out while checking out a connection from connection pool',
           this.address
         );
+        if (options?.timeout) {
+          throw new MongoOperationTimeoutError('Timed out during connection checkout', {
+            cause: timeoutError
+          });
+        }
         throw timeoutError;
       }
       throw error;
+    } finally {
+      if (timeout !== options?.timeout) timeout?.clear();
     }
   }
 
@@ -761,7 +790,6 @@ export class ConnectionPool extends TypedEventEmitter<ConnectionPoolEvents> {
           ConnectionPool.CONNECTION_CHECK_OUT_FAILED,
           new ConnectionCheckOutFailedEvent(this, reason, error)
         );
-        waitQueueMember.timeout.clear();
         this[kWaitQueue].shift();
         waitQueueMember.reject(error);
         continue;
@@ -782,7 +810,6 @@ export class ConnectionPool extends TypedEventEmitter<ConnectionPoolEvents> {
           ConnectionPool.CONNECTION_CHECKED_OUT,
           new ConnectionCheckedOutEvent(this, connection)
         );
-        waitQueueMember.timeout.clear();
 
         this[kWaitQueue].shift();
         waitQueueMember.resolve(connection);
@@ -820,8 +847,6 @@ export class ConnectionPool extends TypedEventEmitter<ConnectionPoolEvents> {
             );
             waitQueueMember.resolve(connection);
           }
-
-          waitQueueMember.timeout.clear();
         }
         process.nextTick(() => this.processWaitQueue());
       });

src/collection.ts

@@ -261,6 +261,11 @@ export class Collection<TSchema extends Document = Document> {
     this.s.collectionHint = normalizeHintField(v);
   }
 
+  /** @internal */
+  get timeoutMS(): number | undefined {
+    return this.s.options.timeoutMS;
+  }
+
   /**
    * Inserts a single document into MongoDB. If documents passed in do not contain the **_id** field,
    * one will be added to each of the documents missing it by the driver, mutating the document. This behavior

src/db.ts

@@ -222,6 +222,11 @@ export class Db {
     return this.s.namespace.toString();
   }
 
+  /** @internal */
+  get timeoutMS(): number | undefined {
+    return this.s.options?.timeoutMS;
+  }
+
   /**
    * Create a new collection on a server with the specified options. Use this to create capped collections.
    * More information about command options available at https://www.mongodb.com/docs/manual/reference/command/create/
@@ -272,6 +277,7 @@ export class Db {
       this.client,
       new RunCommandOperation(this, command, {
         ...resolveBSONOptions(options),
+        timeoutMS: options?.timeoutMS,
         session: options?.session,
         readPreference: options?.readPreference
       })

src/error.ts

@@ -759,6 +759,15 @@ export class MongoUnexpectedServerResponseError extends MongoRuntimeError {
   }
 }
 
+/**
+ * @internal
+ */
+export class MongoOperationTimeoutError extends MongoRuntimeError {
+  override get name(): string {
+    return 'MongoOperationTimeoutError';
+  }
+}
+
 /**
  * An error thrown when the user attempts to add options to a cursor that has already been
  * initialized

src/index.ts

@@ -63,6 +63,7 @@ export {
   MongoNetworkTimeoutError,
   MongoNotConnectedError,
   MongoOIDCError,
+  MongoOperationTimeoutError,
   MongoParseError,
   MongoRuntimeError,
   MongoServerClosedError,

src/operations/command.ts

@@ -65,6 +65,7 @@ export interface OperationParent {
   writeConcern?: WriteConcern;
   readPreference?: ReadPreference;
   bsonOptions?: BSONSerializeOptions;
+  timeoutMS?: number;
 }
 
 /** @internal */
@@ -131,6 +132,7 @@ export abstract class CommandOperation<T> extends AbstractOperation<T> {
     const options = {
       ...this.options,
       ...this.bsonOptions,
+      timeout: this.timeout,
       readPreference: this.readPreference,
       session
     };

src/operations/execute_operation.ts

@@ -24,6 +24,7 @@ import {
 } from '../sdam/server_selection';
 import type { Topology } from '../sdam/topology';
 import type { ClientSession } from '../sessions';
+import { Timeout } from '../timeout';
 import { squashError, supportsRetryableWrites } from '../utils';
 import { AbstractOperation, Aspect } from './operation';
 
@@ -139,9 +140,13 @@ export async function executeOperation<
     selector = readPreference;
   }
 
+  const timeout = operation.timeoutMS != null ? Timeout.expires(operation.timeoutMS) : undefined;
+  operation.timeout = timeout;
+
   const server = await topology.selectServer(selector, {
     session,
-    operationName: operation.commandName
+    operationName: operation.commandName,
+    timeout
   });
 
   if (session == null) {
@@ -252,6 +257,7 @@ async function retryOperation<
   // select a new server, and attempt to retry the operation
   const server = await topology.selectServer(selector, {
     session,
+    timeout: operation.timeout,
     operationName: operation.commandName,
     previousServer
   });

src/operations/find.ts

@@ -116,7 +116,8 @@ export class FindOperation extends CommandOperation<CursorResponse> {
         ...this.options,
         ...this.bsonOptions,
         documentsReturnedIn: 'firstBatch',
-        session
+        session,
+        timeout: this.timeout
       },
       this.explain ? ExplainedCursorResponse : CursorResponse
     );