How to retry HTTP requests with OkHttp/Retrofit?

Question

I am using Retrofit/OkHttp (1.6) in my Android project.

I don\'t find any request retry mechanism built-in to either of them. On searching more, I read OkHttp seems

Answer 1

I found the way(OKHttpClient intercepter) provided by Sinan Kozak does not work when http connection failed, there is nothing yet concerned with HTTP response.

So i use another way to hook the Observable object, call .retryWhen on it. Also, i have added retryCount limit.

import retrofit2.Call;
import retrofit2.CallAdapter;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava.HttpException;
import retrofit2.adapter.rxjava.RxJavaCallAdapterFactory;
import retrofit2.converter.jackson.JacksonConverterFactory;
import rx.Observable;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

Then

    RxJavaCallAdapterFactory originCallAdaptorFactory = RxJavaCallAdapterFactory.create();

    CallAdapter.Factory newCallAdaptorFactory = new CallAdapter.Factory() {
        @Override
        public CallAdapter<?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {

            CallAdapter<?> ca = originCallAdaptorFactory.get(returnType, annotations, retrofit);

            return new CallAdapter<Observable<?>>() {

                @Override
                public Type responseType() {
                    return ca.responseType();
                }

                int restRetryCount = 3;

                @Override
                public <R> Observable<?> adapt(Call<R> call) {
                    Observable<?> rx = (Observable<?>) ca.adapt(call);

                    return rx.retryWhen(errors -> errors.flatMap(error -> {
                        boolean needRetry = false;
                        if (restRetryCount >= 1) {
                            if (error instanceof IOException) {
                                needRetry = true;
                            } else if (error instanceof HttpException) {
                                if (((HttpException) error).code() != 200) {
                                    needRetry = true;
                                }
                            }
                        }

                        if (needRetry) {
                            restRetryCount--;
                            return Observable.just(null);
                        } else {
                            return Observable.error(error);
                        }
                    }));
                }
            };
        }
    };                

Then add or replace

.addCallAdapterFactory(RxJavaCallAdapterFactory.create())

with

.addCallAdapterFactory(newCallAdaptorFactory)

For example:

return new Retrofit
        .Builder()
        .baseUrl(baseUrl)
        .client(okClient)
        .addCallAdapterFactory(newCallAdaptorFactory)
        .addConverterFactory(JacksonConverterFactory.create(objectMapper));

Note: For simplicity, i just treat HTTP code > 404 code as retry, please modify it for yourself.

Besides, if http response is 200, then above rx.retryWhen will not get called, if you insist check such a response, you can add rx.subscribeOn(...throw error... before .retryWhen.