Angular2 HTTP - How to understand that the backend server is down

Question

I am developing a front end which consumes JSON services provided by a server.

I happily use HTTP of Angular2 and I can catch errors via .catch() operator.

Answer 1

Well i have faced something similar before. I was trying to make a logging Service and a Error handling which tells the user if error happened with some requests to the server or if the whole server is down.

I used HTTP Interceptor to catch the responses here is the code:

export class HttpErrorHandlingInterceptor implements HttpInterceptor {
   constructor(private logService: LogService,
               private layoutStateService: LayoutStateService){}
   intercept(
      req: HttpRequest,
      next: HttpHandler
   ): Observable> {
     if (req.url) {
         return next.handle(req).pipe(
                map((event: HttpEvent) => {
                   if (event instanceof HttpResponse) {
                        return event;
                   }
                }),catchError(err => {
                    if(!err.status){
                       this.layoutStateService.dispatchServerDown();
                    }else{
                       this.layoutStateService.dispatchAddServerError(err);
                       this.logService.logError(err);
                    }

               throw err;
             })
        );
    }
  }
}

Now you can specify what should happen when Server is down according to your application. Hope that helps.