Question

我在Android项目中使用Retrofit / OkHttp（1.6）。

我没有找到任何内置于其中任何一个的请求重试机制。在搜索更多时，我看到OkHttp似乎有沉默重试。我在任何连接（HTTP或HTTPS）上都看不到这种情况。如何使用okclient配置重试？

目前，我正在捕获异常并重试维护计数器变量。

Answer 1

For Retrofit 1.x;

您可以使用Interceptors。创建自定义拦截器

    OkHttpClient client = new OkHttpClient();
    client.setConnectTimeout(CONNECT_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);
    client.setReadTimeout(READ_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);
    client.interceptors().add(new Interceptor() {
        @Override
        public Response intercept(Chain chain) throws IOException {
            Request request = chain.request();

            // try the request
            Response response = chain.proceed(request);

            int tryCount = 0;
            while (!response.isSuccessful() && tryCount < 3) {

                Log.d("intercept", "Request is not successful - " + tryCount);

                tryCount++;

                // retry the request
                response = chain.proceed(request);
            }

            // otherwise just pass the original response on
            return response;
        }
    });

在创建RestAdapter时使用它。

new RestAdapter.Builder()
        .setEndpoint(API_URL)
        .setRequestInterceptor(requestInterceptor)
        .setClient(new OkClient(client))
        .build()
        .create(Adapter.class);

对于Retrofit 2.x;

您可以使用Call.clone()方法克隆请求并执行它。

Answer 2

我不知道这是否适合您，但您可以将RxJava与Retrofit一起使用。

Retrofit能够在休息时调用Observables。在Oberservables上，您可以在发出错误时调用retry(count)重新订阅Observable。

您必须在界面中定义调用，如下所示：

@GET("/data.json")
Observable<DataResponse> fetchSomeData();

然后你可以这样订阅这个Observable：

restApi.fetchSomeData()
.retry(5)  // Retry the call 5 times if it errors
.subscribeOn(Schedulers.io())  // execute the call asynchronously
.observeOn(AndroidSchedulers.mainThread())  // handle the results in the ui thread
.subscribe(onComplete, onError); 
// onComplete and onError are of type Action1<DataResponse>, Action1<Throwable>
// Here you can define what to do with the results

我遇到了和你一样的问题，这实际上是我的解决方案。 RxJava是一个非常好的库，可与Retrofit结合使用。除了重试之外，你甚至可以做很多很酷的事情（比如composing and chaining calls）。

Answer 3

response.isSuccessful（）的问题是当你遇到像SocketTimeoutException这样的异常时。

我修改了原始代码以修复它。

OkHttpClient client = new OkHttpClient();
client.setConnectTimeout(CONNECT_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);
client.setReadTimeout(READ_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);
client.interceptors().add(new Interceptor() {
    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        Response response = null;
        boolean responseOK = false;
        int tryCount = 0;

        while (!responseOK && tryCount < 3) {
            try {
                 response = chain.proceed(request);
                 responseOK = response.isSuccessful();                  
            }catch (Exception e){
                 Log.d("intercept", "Request is not successful - " + tryCount);                     
            }finally{
                 tryCount++;      
            }
        }

        // otherwise just pass the original response on
        return response;
    }
});

希望它有所帮助。问候。

Answer 4

我认为您不应将API处理（通过Retrofit / okhttp完成）与重试混合使用。重试机制更加正交，也可以在许多其他上下文中使用。因此，我将Retrofit / OkHTTP用于所有API调用和请求/响应处理，并在上面引入另一层以重试API调用。

到目前为止，根据我有限的Java经验，我发现jhlaterman的Failsafe库（github：jhalterman/failsafe）是一种非常通用的库，可以干净地处理许多“重试”情况。举例来说，这是我如何将其与经过实例化的mySimpleService进行改造以进行身份验证-

AuthenticationResponse authResp = Failsafe.with(
new RetryPolicy().retryOn(Arrays.asList(IOException.class, AssertionError.class))
        .withBackoff(30, 500, TimeUnit.MILLISECONDS)
        .withMaxRetries(3))
.onRetry((error) -> logger.warn("Retrying after error: " + error.getMessage()))
.get(() -> {
    AuthenticationResponse r = mySimpleAPIService.authenticate(
            new AuthenticationRequest(username,password))
            .execute()
            .body();

    assert r != null;

    return r;
});

上面的代码捕获套接字异常，连接错误，断言失败，并对其进行重试（最多3次），并采用指数补偿。它还允许您自定义重试行为，还可以指定回退。它是可配置的，并且可以适应大多数重试情况。

可以随意查看该库的文档，因为它提供了许多其他功能（除了重试之外）。

Answer 5

礼貌地回答，这对我有用。如果存在连接问题，最好在重试前等待几秒钟。

public class ErrorInterceptor implements Interceptor {
ICacheManager cacheManager;
Response response = null;
int tryCount = 0;
int maxLimit = 3;
int waitThreshold = 5000;
@Inject
public ErrorInterceptor() {

}

@Override
public Response intercept(Chain chain){

   // String language =  cacheManager.readPreference(PreferenceKeys.LANGUAGE_CODE);
  Request request = chain.request();
  response =  sendReqeust(chain,request);
    while (response ==null && tryCount < maxLimit) {
        Log.d("intercept", "Request failed - " + tryCount);
        tryCount++;
        try {
            Thread.sleep(waitThreshold); // force wait the network thread for 5 seconds
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
       response = sendReqeust(chain,request);
    }
    return response;
}

private Response sendReqeust(Chain chain, Request request){
    try {
        response = chain.proceed(request);
        if(!response.isSuccessful())
            return null;
        else
        return response;
    } catch (IOException e) {
      return null;
    }
}

}

Answer 6

我发现当http连接失败时，Sinan Kozak提供的方式（OKHttpClient intercepter）不起作用，还没有关注HTTP响应。

所以我用另一种方法来挂钩Observable对象，在它上面调用.retryWhen。另外，我添加了retryCount限制。

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;

然后

    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);
                        }
                    }));
                }
            };
        }
    };

然后添加或替换

.addCallAdapterFactory(RxJavaCallAdapterFactory.create())

与

.addCallAdapterFactory(newCallAdaptorFactory)

例如：

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

注意：为简单起见，我只是对待HTTP代码＆gt; 404代码重试，请自行修改。

此外，如果http响应为200，则上述rx.retryWhen将不会被调用，如果您坚持检查此类响应，则可以在.retryWhen之前添加rx.subscribeOn(...throw error...。

Answer 7

对于那些喜欢拦截器来处理重试问题的人 - 根据Sinan的回答，这是我提出的拦截器，它包括重试计数和退避延迟，并且只在网络可用时重试尝试，并且在请求未被取消时重试。（仅处理IOExceptions（SocketTimeout，UnknownHost等））

pip install --upgrade pip

Answer 8

它似乎将出现在API Spec的改进2.0中： https://github.com/square/retrofit/issues/297。目前，最好的方法似乎是捕获异常并手动重试。

Answer 9

正如docs中所述，更好的方法是在身份验证器中使用烘焙，例如： private final OkHttpClient client = new OkHttpClient（）;

  public void run() throws Exception {
    client.setAuthenticator(new Authenticator() {
      @Override public Request authenticate(Proxy proxy, Response response) {
        System.out.println("Authenticating for response: " + response);
        System.out.println("Challenges: " + response.challenges());
        String credential = Credentials.basic("jesse", "password1");
        return response.request().newBuilder()
            .header("Authorization", credential)
            .build();
      }

      @Override public Request authenticateProxy(Proxy proxy, Response response) {
        return null; // Null indicates no attempt to authenticate.
      }
    });

    Request request = new Request.Builder()
        .url("http://publicobject.com/secrets/hellosecret.txt")
        .build();

    Response response = client.newCall(request).execute();
    if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

    System.out.println(response.body().string());
  }

Answer 10

我已经玩了很多这个问题试图找到重试改造请求的最佳方法。我正在使用Retrofit 2，所以我的解决方案是Retrofit 2.对于Retrofit 1，你必须使用Interceptor，就像这里接受的答案一样。 @joluet的答案是正确的，但他没有提到需要在.subscribe（onComplete，onError）方法之前调用重试方法。这非常重要，否则请求不会像@joluet中提到的@pocmo那样再次重试。这是我的例子：

final Observable<List<NewsDatum>> newsDetailsObservable = apiService.getCandidateNewsItem(newsId).map((newsDetailsParseObject) -> {
                    return newsDetailsParseObject;
                });

newsDetailsObservable.subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .retry((integer, throwable) -> {
                //MAX_NUMBER_TRY is your maximum try number
                if(integer <= MAX_NUMBER_TRY){
                    return true;//this will retry the observable (request)
                }
                return false;//this will not retry and it will go inside onError method
            })
            .subscribe(new Subscriber<List<NewsDatum>>() {
                @Override
                public void onCompleted() {
                    // do nothing
                }

                @Override
                public void onError(Throwable e) {
                   //do something with the error
                }

                @Override
                public void onNext(List<NewsDatum> apiNewsDatum) {
                    //do something with the parsed data
                }
            });

apiService是我的RetrofitServiceProvider对象。

BTW：我使用的是Java 8，所以代码中有很多lambda表达式。

Answer 11

只想分享我的版本。它使用rxJava retryWhen方法。我的版本每N = 15秒重试一次连接，并在互联网连接恢复时几乎立即发出重试。

public class RetryWithDelayOrInternet implements Function<Flowable<? extends Throwable>, Flowable<?>> {
public static boolean isInternetUp;
private int retryCount;

@Override
public Flowable<?> apply(final Flowable<? extends Throwable> attempts) {
    return Flowable.fromPublisher(s -> {
        while (true) {
            retryCount++;
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                attempts.subscribe(s);
                break;
            }
            if (isInternetUp || retryCount == 15) {
                retryCount = 0;
                s.onNext(new Object());
            }
        }
    })
            .subscribeOn(Schedulers.single());
}}

你应该在之前使用它.subscribe如下：

.retryWhen(new RetryWithDelayOrInternet())

您应该手动更改isInternetUp字段

public class InternetConnectionReceiver extends BroadcastReceiver {


@Override
public void onReceive(Context context, Intent intent) {
    boolean networkAvailable = isNetworkAvailable(context);
    RetryWithDelayOrInternet.isInternetUp = networkAvailable;
}
public static boolean isNetworkAvailable(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}}

Answer 12

在OkHttp 3.9.1上对我有用的解决方案（考虑此问题的其他答案）：

@NonNull
@Override
public Response intercept(@NonNull Chain chain) throws IOException {
    Request  request      = chain.request();
    int      retriesCount = 0;
    Response response     = null;

    do {
        try {
            response = chain.proceed(request);

        // Retry if no internet connection.
        } catch (ConnectException e) {
            Log.e(TAG, "intercept: ", e);
            retriesCount++;

            try {
                Thread.sleep(RETRY_TIME);

            } catch (InterruptedException e1) {
                Log.e(TAG, "intercept: ", e1);
            }
        }

    } while (response == null && retriesCount < MAX_RETRIES);

    // If there was no internet connection, then response will be null.
    // Need to initialize response anyway to avoid NullPointerException.
    if (response == null) {
        response = chain.proceed(newRequest);
    }

    return response;
}

Answer 13

工作产品解决方案。

public int callAPI() {
    return 1; //some method to be retried
}

public int retrylogic()  throws InterruptedException, IOException{
    int retry = 0;
    int status = -1;
    boolean delay = false;
    do {
        if (delay) {
            Thread.sleep(2000);
        }

        try {
            status = callAPI();
        }
        catch (Exception e) {
            System.out.println("Error occured");
            status = -1;
        }
        finally {
            switch (status) {
            case 200:
                System.out.println(" **OK**");
                return status; 
            default:
                System.out.println(" **unknown response code**.");
                break;
            }
            retry++;
            System.out.println("Failed retry " + retry + "/" + 3);
            delay = true;

        } 
    }while (retry < 3);

    System.out.println("Aborting download of dataset.");
    return status;
}

Answer 14

正如以前的用户所说，如果您使用的是 Retrofit2 call.clone 就足够了，但我还想添加一个简单的示例来说明它的外观：

public class CallbackImpl implements Callback<ResponseBody> {
    private final Set<Integer> retryCode = new HashSet<>(Arrays.asList(503, 504));
    int requestRetry  = 1;

    @Override
    public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
        if (response.code() == 201) {
            // Object was created.
        } else {
            if (requestRetry != 0 && retryCode.contains(response.code())) {
                call.clone().enqueue(this);
            } else {
                // Handle the error
            }
        }
    }

    @Override
    public void onFailure(Call<ResponseBody> call, Throwable throwable) {
        if (throwable instanceof IOException) {
            // Network failure
        } else {
            // Conversion Issue
        }
    }
}

如何使用OkHttp / Retrofit重试HTTP请求？

14 个答案: