Buffering requests to the same resource

buffered-requester.ts

class Requester {
  /** Intermediate observable used to prepare fetching connector identifiers and updating `connectorIdentifiers$`. */
  protected readonly fetchConnectorIdentifiers$ = new Subject<number>();

  constructor() {
    /**
     * When idle and an identifiers fetch request comes in, this waits 100ms before triggering.
     * When just received a value (within the 100ms window), these do not increase the window timeout.
     */
    const fetchConnectorIdentifiersTimer$ = this.fetchConnectorIdentifiers$.pipe(mapTo(undefined), auditTime(100));

    /**
     * Buffers identifier fetch requests for the time given by the `fetchConnectorIdentifiersTimer$`, then fetches
     * all requested identifiers at once. This must be done, as many labels possibly request the UUID concurrently.
     */
    this.fetchConnectorIdentifiers$.pipe(bufferWhen(() => fetchConnectorIdentifiersTimer$)).subscribe(async connectorIds => {
      await this.immediateUpdateConnectorUuidsByIds(connectorIds);
    }); 
  }
  
  
  /**
   * Fetches the identifiers for the given connector ID, i.e. an object of both the ID and the UUID,
   * then updates `connectorIdentifiers$` with the new values. The update is buffered and the effect
   * can be observed with `getConnectorUuidById`.
   */
  public updateConnectorUuidById(connectorId: number) {
    if (connectorId > -1) {
      this.fetchConnectorIdentifiers$.next(connectorId);
    }
  }
}