Angular Polling Service

angular-poolling.service.ts

import { Inject, Injectable, InjectionToken } from '@angular/core';

import { Observable, combineLatest, filter, interval, take, takeWhile } from 'rxjs';

// REQUEST_INTEVAL and MAX_QUANTITY_ATTEMPTS are InjectionToken
// InjectionTokens can be configured globally at the module, component or service level only once

// defines a interval in seconds to api request
export const REQUEST_INTEVAL = new InjectionToken<number>('REQUEST_INTEVAL', {
  providedIn: 'root',
  factory: () => 2000
});

// defines a max quantity of attempts
// if the api not responds with a successful response in the max quantity of attempts, the service stop the requests
export const MAX_QUANTITY_ATTEMPTS = new InjectionToken<number>('MAX_QUANTITY_ATTEMPTS', {
  providedIn: 'root',
  factory: () => 10
});


@Injectable({ providedIn: 'root' })
export class PoollingService {

  constructor(
    @Inject(REQUEST_INTEVAL) private requestInterval: number,
    @Inject(MAX_QUANTITY_ATTEMPTS) private maxQuantityAttempts: number
  ) {}

  poll<T>(observable$: Observable<T>) {
    return combineLatest([observable$.pipe(take(1)), interval(this.requestInterval)]).pipe(
      take(this.maxQuantityAttempts),
      takeWhile(
        response => /* Adds the condition to stop the service */,
        true
      ),
      filter(response => /* Adds the condition for not emit values for subscription */)
    );
  }
}