OkHttp Call timeout from Retrofit Interceptor using Annotations is not applied

Question

I'm trying to use a recently added feature from OkHttp 3.12.0: full-operation timeouts. For that, I also rely on the new Invocation class from retrofit 2.5.0 that allows me to retrieve the method annotations.

The annotation is:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Timeout {

    int value();

    TimeUnit unit();

}

The retrofit interface is:

public interface AgentApi {

    @Timeout(value = 100, unit = TimeUnit.MILLISECONDS)
    @GET("something")
    Call<String> getSomething();

}

And the interceptor is:

class TimeoutInterceptor implements Interceptor {

    @NonNull
    @Override
    public Response intercept(@NonNull Chain chain) throws IOException {
        Request request = chain.request();
        final Invocation tag = request.tag(Invocation.class);
        final Method method = tag != null ? tag.method() : null;
        final Timeout timeout = method != null ? method.getAnnotation(Timeout.class) : null;
        if (timeout != null) {
            chain.call().timeout().timeout(timeout.value(), timeout.unit());
        }
        return chain.proceed(request);
    }

}

I've correctly added the TimeoutInterceptor with .addInterceptor(...) in the OkHttpClient provided to the Retrofit Builder.

Unfortunately, it doesn't work as I expected. The calls are not failing when the timeout is reached?

Though it works fine when using the chain methods from the interceptor:

chain
  .withConnectTimeout(connect, unit)
  .withReadTimeout(read, unit)
  .withWriteTimeout(write, unit)

Is this because the call timeout must be set before the call is enqueued? (and the Interceptor is triggered too late in the process?), or is this something else?

Answer 1

Unfortunately you are right. It is because OkHttpClient gets timeouts before it executes interceptors chain. If you look at Response execute() method in okhttp3.RealCall class you will find line timeout.enter() that is where OkHttp schedules timeouts and it is invoked before getResponseWithInterceptorChain() which is place where interceptors are executed.

Fortunately you can write workaround for that :) Put your TimeoutInterceptor in okhttp3 package (you can create that package in your app). That will allow you to have access to RealCall object which has package visibility. Your TimeoutInterceptor class should look like this:

package okhttp3;

public class TimeoutInterceptor implements Interceptor {

   @Override
   public Response intercept(Chain chain) throws IOException {
       Request request = chain.request();
       Invocation tag = request.tag(Invocation.class);
       Method method = tag != null ? tag.method() : null;
       Timeout timeout = method != null ? method.getAnnotation(Timeout.class) : null;
       if (timeout != null) {
           chain.call().timeout().timeout(timeout.value(), timeout.unit());
           RealCall realCall = (RealCall) chain.call();
           realCall.timeout.enter();
       }
       return chain.proceed(request);
   }
}

Workaround consists in executing timeout.enter() once again after changing timeout. All magic happen in lines:

RealCall realCall = (RealCall) chain.call();
realCall.timeout.enter();

Good luck!