RXJava repeat request if response is not successful and continue stream

Question

I need to make a request to a webserver and the server usually returns a reference code that i use in the stream. But sometimes the server is busy and returns an error indicating that it's busy so that i have to retry in a few moments.

public static Single<List<iIB>> run()
{
    //First retrieve reference code from IB
    return IBRepository.getInstance().getReferenceCode()
                .doOnSuccess(s -> Log.d(AppConstants.AppTag, "Success: " + s))
                .doOnError(s -> Log.d(AppConstants.AppTag, "Error: " + s))

            //Once reference code is retrieved, make second request to get XML report as string
        .flatMap((Function<String, SingleSource<String>>) referenceCode -> IBRepository.getInstance().getXMLReport(referenceCode))
        
        ...
}


/**
 * This method makes the first request to IB to get the reference code for the flex query in case of success
 * Sometimes server is busy and ask to retry the request in a few moments so we return an error indicating the cause
 * @return an observable string containing the reference code to download the XMLParser report in IB
 */
public Single<String> getReferenceCode()
{
    final String REF_CODE = "ReferenceCode";
    final String STATUS = "Status";
    final String FAIL = "Fail";
    final String ERROR_MESSAGE = "ErrorMessage";

    return Single.fromObservable(_Volley.getInstance().postRxVolley(IBConstants.QUERY_REQUEST_URL)
            .flatMap((Function<Result, ObservableSource<String>>) Response::processResultResponse)
            .flatMapSingle((Function<String, SingleSource<String>>) xmlResponse ->
            {
                Document xmlDocument = XMLParser.convertStringToXMLDocument(xmlResponse);

                if(xmlDocument == null)
                    return Single.error(new Throwable("Error with DOM XML Library"));
                else if(!XMLParser.getSingleValueFromTag(xmlDocument, STATUS, 0).contains(FAIL))
                    return Single.just(XMLParser.getSingleValueFromTag(xmlDocument, REF_CODE, 0));
                else
                    return Single.error(new Throwable(XMLParser.getSingleValueFromTag(xmlDocument, ERROR_MESSAGE, 0)));
            }));
}

What i'm trying to achieve is to retry the call to getReferenceCode() after some time if that method returns an error. Could this be achievable using RxJava operators?

Thanks

Answer 1

You can use RxJava2 retryWhen operator and set the condition you want to retry your api call.

• http://reactivex.io/documentation/operators/retry.html

You can check this blog for your reference

• https://pamartinezandres.com/rxjava-2-exponential-backoff-retry-only-when-internet-is-available-5a46188ab175