Leveraging Angular's Observables to Defer Multiple API Requests within a Specified Timeframe

Question

Leveraging Angular's Observables to Defer Multiple API Requests within a Specified Timeframe

In my Angular 4 app, I have a setup like this (for illustration purposes, I've omitted some code)

@Injectable()
  export class SomeService {

    constructor(
      private http: Http
    ) {
    }

    get(id: number) {
      return this.http.get('http://somedomain/somemodel/${id}.json');
    }

  }

This service is utilized by various components to make API calls.

constructor(private someService: SomeService) {}
  ...
  someMethod() {
    // code here...
    this.someService.get(2).subscribe( someHandlerFunction );
  }

  someOtherMethod() {
    // more code here...
    this.someService.get(2).subscribe( someHandlerFunction );
  }

The issue at hand is uncertainty around the timing of when someMethod() and someOtherMethod() will be triggered. Sometimes both may be initiated, resulting in two API calls. My aim is to find a way to modify the Service so that the request is only made after a specified timeframe. I attempted to use debounce:

get(id: number) {
    return this.http.get(`http://somedomain/somemodel/${id}.json`).debounceTime(10000);
  }

I expected that with this approach, the HTTP get request would only occur once every 10 seconds. If a new request is sent within this interval, it would not trigger another call but rather emit the latest value from the observable. However, this method didn't provide the desired outcome. Any suggestions?

PS: While I understand that utilizing a flag could help manage this, it proves to be inefficient as my application has multiple services handling numerous HTTP requests.

Your thoughts on this?

javascript angular typescript rxjs observable

Answer 1

Answer №1

It is recommended to apply debounce on the observable triggering the http service, rather than directly on the http request itself. This way, you can achieve a smoother flow of events.

myObservable
  .changes
  .debounceTime(800)
  .subscribe(// Make the http call here)

You can find a more detailed explanation on this topic in a related discussion here.

Answer 2

It is recommended to apply debounce on the observable triggering the http service, rather than directly on the http request itself. This way, you can achieve a smoother flow of events.

myObservable
  .changes
  .debounceTime(800)
  .subscribe(// Make the http call here)

You can find a more detailed explanation on this topic in a related discussion here.

Answer 3

Answer №2

One way to optimize your application with RxJS is by implementing caching for your results. By setting up an interval that clears the cache periodically, you ensure that new requests can be made without overloading your server or database. This strategy is especially useful for preventing redundant queries every time a page is loaded, particularly when no new data has been added.

While this approach may require more code than other solutions, it offers several advantages:

Efficiently caching results helps reduce the load on your server and database.
Unlike simply using debounceTime, this method not only blocks requests but also provides cached results. By utilizing this technique, you can still access previous data if needed while delaying new requests until necessary.

Implementing result caching:

Class ProjectService {
    private cachedProjects: Observable<Project[]>;

    all(): Observable<Project[]> {
        if (!this.cachedProjects) {
            this.cachedProjects = this.httpService.get(`${this.url}/project`)
                .map(res => res.data.map(project => new Project(project)))
                .publishReplay()
                .refCount();
        }

        return this.cachedProjects;
    }
}

When calling the service:

this.projectService.all().subscribe((projects: Project[]) => {
    // The initial call will fetch 'projects', subsequent calls will use cached data
});

To control how frequently HTTP calls are blocked, you can introduce an interval mechanism in your service. Update your service as shown below:

Class ProjectService {
    private cachedProjects: Observable<Project[]>;

    constructor() {
        setInterval(() => {
            this.cachedProjects = null;
        }, 5000); // Set interval to clear cache every 5 seconds
    }

    all(): Observable<Project[]> {
        if (!this.cachedProjects) {
            this.cachedProjects = this.httpService.get(`${this.url}/project`)
                .map(res => res.data.map(project => new Project(project)))
                .publishReplay()
                .refCount();
        }

        return this.cachedProjects;
    }
}

With this setup, you can make fresh requests every 5 seconds while leveraging cached projects during intervals.

Answer 4

One way to optimize your application with RxJS is by implementing caching for your results. By setting up an interval that clears the cache periodically, you ensure that new requests can be made without overloading your server or database. This strategy is especially useful for preventing redundant queries every time a page is loaded, particularly when no new data has been added.

While this approach may require more code than other solutions, it offers several advantages:

Efficiently caching results helps reduce the load on your server and database.
Unlike simply using debounceTime, this method not only blocks requests but also provides cached results. By utilizing this technique, you can still access previous data if needed while delaying new requests until necessary.

Implementing result caching:

Class ProjectService {
    private cachedProjects: Observable<Project[]>;

    all(): Observable<Project[]> {
        if (!this.cachedProjects) {
            this.cachedProjects = this.httpService.get(`${this.url}/project`)
                .map(res => res.data.map(project => new Project(project)))
                .publishReplay()
                .refCount();
        }

        return this.cachedProjects;
    }
}

When calling the service:

this.projectService.all().subscribe((projects: Project[]) => {
    // The initial call will fetch 'projects', subsequent calls will use cached data
});

To control how frequently HTTP calls are blocked, you can introduce an interval mechanism in your service. Update your service as shown below:

Class ProjectService {
    private cachedProjects: Observable<Project[]>;

    constructor() {
        setInterval(() => {
            this.cachedProjects = null;
        }, 5000); // Set interval to clear cache every 5 seconds
    }

    all(): Observable<Project[]> {
        if (!this.cachedProjects) {
            this.cachedProjects = this.httpService.get(`${this.url}/project`)
                .map(res => res.data.map(project => new Project(project)))
                .publishReplay()
                .refCount();
        }

        return this.cachedProjects;
    }
}

With this setup, you can make fresh requests every 5 seconds while leveraging cached projects during intervals.

Answer 5

Answer №3

I encountered a similar problem, and my approach involved creating an rxjs subject to emit an id.

@Injectable()
export class SomeService {
  private idSubject = new Subject<string>();
  
  constructor(private http: Http) {
    this.idSubject.asObservable().distinctUntilChange()
        .subscribe((id) => {
              this.http.get('http://somedomain/somemodel/${id}.json')
            });
  }

  get(id: number) {
    this.idSubject.next(id);
  }
}

Although my solution may not be an exact match for your requirements, you have the flexibility to customize it according to your specific needs.

Answer 6

I encountered a similar problem, and my approach involved creating an rxjs subject to emit an id.

@Injectable()
export class SomeService {
  private idSubject = new Subject<string>();
  
  constructor(private http: Http) {
    this.idSubject.asObservable().distinctUntilChange()
        .subscribe((id) => {
              this.http.get('http://somedomain/somemodel/${id}.json')
            });
  }

  get(id: number) {
    this.idSubject.next(id);
  }
}

Although my solution may not be an exact match for your requirements, you have the flexibility to customize it according to your specific needs.

Leveraging Angular's Observables to Defer Multiple API Requests within a Specified Timeframe

Answer №1

Answer №2

Answer №3

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