Method checkOut

src/cmap/connection_pool.ts:321–377

* Check a connection out of this pool. The connection will continue to be tracked, but no reference to it * 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.

(options: { timeoutContext: TimeoutContext } & Abortable)

   * explicitly destroyed by the new owner.
   */
  async checkOut(options: { timeoutContext: TimeoutContext } & Abortable): Promise<Connection> {
    const checkoutTime = processTimeMS();
    this.emitAndLog(
      ConnectionPool.CONNECTION_CHECK_OUT_STARTED,
      new ConnectionCheckOutStartedEvent(this)
    );

    const { promise, resolve, reject } = promiseWithResolvers<Connection>();

    const timeout = options.timeoutContext.connectionCheckoutTimeout;

    const waitQueueMember: WaitQueueMember = {
      resolve,
      reject,
      cancelled: false,
      checkoutTime
    };

    const abortListener = addAbortListener(options.signal, function () {
      waitQueueMember.cancelled = true;
      reject(this.reason);
    });

    this.waitQueue.push(waitQueueMember);
    queueMicrotask(() => this.processWaitQueue());

    try {
      timeout?.throwIfExpired();
      return await (timeout ? Promise.race([promise, timeout]) : promise);
    } catch (error) {
      if (TimeoutError.is(error)) {
        timeout?.clear();
        waitQueueMember.cancelled = true;

        this.emitAndLog(
          ConnectionPool.CONNECTION_CHECK_OUT_FAILED,
          new ConnectionCheckOutFailedEvent(this, 'timeout', waitQueueMember.checkoutTime)
        );
        const timeoutError = new WaitQueueTimeoutError(
          this.loadBalanced
            ? this.waitQueueErrorMetrics()
            : 'Timed out while checking out a connection from connection pool',
          this.address
        );
        if (options.timeoutContext.csotEnabled()) {
          throw new MongoOperationTimeoutError('Timed out during connection checkout', {
            cause: timeoutError
          });
        }
        throw timeoutError;
      }
      throw error;
    } finally {
      abortListener?.[kDispose]();
      timeout?.clear();
    }
  }