Function fetchBatch

src/cursor/abstract_cursor.ts:940–984

@internal Attempt to obtain more documents

()

  /** @internal Attempt to obtain more documents */
  private async fetchBatch(): Promise<void> {
    if (this.isClosed) {
      return;
    }

    if (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
    try {
      const response = await this.getMore();
      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) {