Retrofit + RxJava无法缓存响应，可疑的响应头

Question

I'm trying to configure cache with Retrofit 1.9.0 and OkHtttp 2.5.0 .

Here is how I provide OkHttpClient for my RestAdapter :

@Provides
@Singleton
public OkHttpClient provideOkHttpClient() {
    OkHttpClient okHttpClient = new OkHttpClient();
    okHttpClient.setConnectTimeout(TIMEOUT_IN_SECONDS, TimeUnit.SECONDS);
    okHttpClient.setReadTimeout(TIMEOUT_IN_SECONDS, TimeUnit.SECONDS);
    okHttpClient.setWriteTimeout(TIMEOUT_IN_SECONDS, TimeUnit.SECONDS);

    File cacheDir = new File(context.getCacheDir(), "http");
    final Cache cache = new Cache(cacheDir, DISK_CACHE_SIZE_IN_BYTES);
    okHttpClient.setCache(cache);

    okHttpClient.interceptors().add(new Interceptor() {
        @Override
        public Response intercept(Chain chain) throws IOException {

            Response response = chain.proceed(request);
            Response finalResponse = response.newBuilder()
                    .header("Cache-Control", String.format("public, max-stale=%d", 604800))
                    .build();

            Log.d("OkHttp", finalResponse.toString());
            Log.d("OkHttp Headers", finalResponse.headers().toString());
            return finalResponse;
        }
    });

    return okHttpClient;
}

I did not forget to setClient on RestAdapter.Builder . Also made sure, that I'm actually using instance of RestAdapter with this client set.

Even checked if the files are created under "http" folder. They are.

However after I turn of WIFI and reload my screen I end up in OnError callback of Observable endpoint with this message:

retrofit.RetrofitError: failed to connect to /10.40.31.12 (port 8888) after 10000ms: connect failed: ENETUNREACH (Network is unreachable)

DISCLAIMER: I should probably mention that the final Observable is combined from 5 others, with flatMap and zip on the way.

Answer 1

I think I have an answer. Short one is: "Cannot be done if server sends no-cache header in response".

If you want the longer one, details are below.

I've made a sample app comparing 2 backends. Lets call them Backend A, and Backend B. A was giving me troubles so I've decided to check on B.

A returns CacheControl = "no-cache, no-transform, max-age=0"

B returns Cache-Control = „public" response header

I did the same setup for both backends, just different urls.

    private void buildApi() {
        Gson gson = new GsonBuilder().create();

        OkHttpClient okHttpClient = new OkHttpClient();
        okHttpClient.setConnectTimeout(10, TimeUnit.SECONDS);

        File cacheDir = new File(getCacheDir(), "http");
        final Cache cache = new Cache(cacheDir, 1000000 * 10);
        okHttpClient.setCache(cache);

        okHttpClient.interceptors().add(new Interceptor() {
            @Override
            public Response intercept(Chain chain) throws IOException {
                Request request = chain.request();
                Log.d("OkHttp REQUEST", request.toString());
                Log.d("OkHttp REQUEST Headers", request.headers().toString());

                Response response = chain.proceed(request);
                response = response.newBuilder()
                        .header("Cache-Control", String.format("public, max-age=%d, max-stale=%d", 60, RESPONSE_CACHE_LIFESPAN_IN_SECONDS))
                        .build();

                Log.d("OkHttp RESPONSE", response.toString());
                Log.d("OkHttp RESPONSE Headers", response.headers().toString());
                return response;
            }
        });

        RestAdapter.Builder builder = new RestAdapter.Builder()
                .setConverter(new StringGsonConverter(gson))
                .setClient(new OkClient(okHttpClient))
                .setRequestInterceptor(new RequestInterceptor() {
                    @Override
                    public void intercept(RequestFacade request) {

                        if (isNetworkAvailable()) {
                            request.addHeader("Cache-Control", "public, max-age=" + 60);
                        } else {
                            request.addHeader("Cache-Control", "public, only-if-cached, max-stale=" + RESPONSE_CACHE_LIFESPAN_IN_SECONDS);
                        }
                    }
                });

        builder.setEndpoint("http://this.is.under.vpn.so.wont.work.anyway/api");
        A_API = builder.build().create(AApi.class);

        builder.setEndpoint("http://collector-prod-server.elasticbeanstalk.com/api");
        B_API = builder.build().create(BApi.class);
    }

Did both calls, then disabled wifi. Cache worked fine for B, but A thrown 504 Unsatisfiable Request (only-if-cached)

It seems that overwritting headers won't help in that case.

Answer 2

You should rewrite your Request instead of the Response . For reference, see the docs on rewriting requests . Note you, can also use the CacheControl class instead of building your own header if you want. Your interceptor should look something like --

okHttpClient.interceptors().add(new Interceptor() {
  @Override
  public Response intercept(Chain chain) throws IOException {

    Request request = chain.request();
    Request cachedRequest = request.newBuilder()
        .cacheControl(new CacheControl.Builder()
            .maxStale(7, TimeUnit.DAYS)
            .build())
        .build();

    return chain.proceed(cachedRequest);
  }
});