Chain 2 calls with retry using RxAndroid

Question

My use case is: I have an Android app, I need to call one api, when that data becomes available call the second api. For this I was planning to use RxAndroid, with retries.

I was able to do 1 api call with retries, but I need to chain the 2, and be able to show 2 different errors, one for call 1 not available, and one for call2 not available.

I can have the retry either on the whole chain, but I would prefer to retry each operation individually.

My code is as follow, I need to add a "callApi1()" before the callApi2, and I would prefer, like I said to have a different observable with retries.

  Observable.create(new Observable.OnSubscribe<String>() {
                @Override
                public void call(Subscriber<? super String> subscriber) {
                    try {
                        subscriber.onNext(callApi2());
                        subscriber.onCompleted();
                    } catch (Exception e) {
                        subscriber.onError(e);
                    }
                }
            })
            .retryWhen(new RetryWithDelay(20, 3000))
            .timeout(TIME_OUT_SECONDS, TimeUnit.SECONDS)
            .observeOn(AndroidSchedulers.mainThread())
            .subscribeOn(Schedulers.io())
            .subscribe(new Subscriber<String>() {
                @Override
                public void onNext(String data) {
                       //show something
                }
             ....
             }

Answer 1

You could use the Observable.concat operator eg

Observable<String> obs1 = Observable.create(new Observable.OnSubscribe<String>() {
            @Override
            public void call(Subscriber<? super String> subscriber) {
                try {
                    subscriber.onNext(callApi1());
                    subscriber.onCompleted();
                } catch (Exception e) {
                    subscriber.onError(e);
                }
            }
        })
        .timeout(TIME_OUT_SECONDS, TimeUnit.SECONDS)
        .retryWhen(new RetryWithDelay(20, 3000))            
        .subscribeOn(Schedulers.io());

Observable<String> obs2 = Observable.create(new Observable.OnSubscribe<String>() {
            @Override
            public void call(Subscriber<? super String> subscriber) {
                try {
                    subscriber.onNext(callApi2());
                    subscriber.onCompleted();
                } catch (Exception e) {
                    subscriber.onError(e);
                }
            }
        })
        .timeout(TIME_OUT_SECONDS, TimeUnit.SECONDS)
        .retryWhen(new RetryWithDelay(20, 3000))            
        .subscribeOn(Schedulers.io());

Observable<String> chained = Observable.concat(obs1,obs2);