angular2 rxjs observable forkjoin

You could leverage the catch operator for each observable to intercept the error and return another observable in such cases.

Here is a sample:

return Observable.forkJoin(  this.http.get('/some-url')         .map((res:Response) => res.json())         .catch(res:Response => Observable.of({}),  this.http.get('/some-other-url')         .map((res:Response) => res.json())         .catch(res:Response => Observable.of({}),);

Uses Observable.forkJoin() to run multiple concurrent http.get() requests. The entire operation will result in an error state if any single request fails.

 getBooksAndMovies() {    return Observable.forkJoin(      this.http.get('/app/books.json').map((res:Response) => res.json()),      this.http.get('/app/movies.json').map((res:Response) => res.json())    );

But you could put your additional GET request in the error handler:

getBooksAndMovies() {    Observable.forkJoin(        this.http.get('/app/books.json').map((res:Response) => res.json()),        this.http.get('/app/movies.json').map((res:Response) => res.json())    ).subscribe(      data => {        this.books = data[0]        this.movies = data[1]      },      err => console.error(err)    );