实现HttpClient重试

分手后的思念是犯贱 2022-06-07 00:35 241阅读 0赞

## 场景应用 ##

目前程序中涉及到需要callback操作，product需要被动的接收consume的处理状态，为了最大程度的能够callback成功因此consume在http调用出现问题（如：服务不可用、异常、超时）情况下需要进行重试（retry request）。

### 1、针对异常的重试 ###

例如：connect timed out/read timed out

HttpClientBuilder.create()
                    .setRetryHandler(new HttpRequestRetryHandler() {
                        @Override
                        public boolean retryRequest(IOException exception, int executionCount, HttpContext context) {
                            if (executionCount >= 3) {
                                // Do not retry if over max retry count
                                return false;
                            }
                            return true;
                        }
    				)
                    .setConnectionManager(new PoolingHttpClientConnectionManager())
                    .setDefaultRequestConfig(requestConfig)
                    .build();

如此实现针对异常进行3次重试的效果

### 2、针对响应错误码进行重试 ###

例如400/500等

首先需要定义一个重试策略类：

package com.gomefinance.esign.httpretry;
    
    import org.apache.http.HttpResponse;
    import org.apache.http.client.ServiceUnavailableRetryStrategy;
    
    /**
     * 针对请求地址可达，非200 响应码进行重试
     */
    
    public class MyServiceUnavailableRetryStrategy implements ServiceUnavailableRetryStrategy {
    
        private int executionCount;
        private long retryInterval;
    
        MyServiceUnavailableRetryStrategy(Builder builder) {
            this.executionCount = builder.executionCount;
            this.retryInterval = builder.retryInterval;
        }
    
        /**
         * retry逻辑
         */
        @Override
        public boolean retryRequest(HttpResponse response, int executionCount, org.apache.http.protocol.HttpContext context) {
            if (response.getStatusLine().getStatusCode() != 200 && executionCount < executionCount)
                return true;
            else
                return false;
        }
    
        /**
         * retry间隔时间
         */
        @Override
        public long getRetryInterval() {
            return this.retryInterval;
        }
    
        public static final class Builder {
            private int executionCount;
            private long retryInterval;
    
            public Builder() {
                executionCount = 3;
                retryInterval = 1000;
            }
    
            public Builder executionCount(int executionCount) {
                this.executionCount = executionCount;
                return this;
            }
    
            public Builder retryInterval(long retryInterval) {
                this.retryInterval = retryInterval;
                return this;
            }
    
            public MyServiceUnavailableRetryStrategy build() {
                return new MyServiceUnavailableRetryStrategy(this);
            }
        }
    
    
    }

之后需要如下

ServiceUnavailableRetryStrategy serviceUnavailableRetryStrategy = new MyServiceUnavailableRetryStrategy.Builder()
                    .executionCount(3)
                    .retryInterval(1000)
                    .build();
    HttpClientBuilder.create()
                    .setServiceUnavailableRetryStrategy(serviceUnavailableRetryStrategy)
                    .setConnectionManager(new PoolingHttpClientConnectionManager())
                    .setDefaultRequestConfig(requestConfig)
                    .build();

即可实现针对错误码的异常处理

### 3、针对错误和错误码进行处理 ###

ServiceUnavailableRetryStrategy serviceUnavailableRetryStrategy = new MyServiceUnavailableRetryStrategy.Builder()
                    .executionCount(3)
                    .retryInterval(1000)
                    .build();
            httpClient = HttpClientBuilder.create()
                    .setRetryHandler((e,executionCount,contr)->{
                        if (executionCount >= 3) {
                            // Do not retry if over max retry count
                            return false;
                        }
                        return true;
                    })
                    .setServiceUnavailableRetryStrategy(serviceUnavailableRetryStrategy)
                    .setConnectionManager(new PoolingHttpClientConnectionManager())
                    .setDefaultRequestConfig(requestConfig)
                    .build();

以上就是针对HttpClient重试的方式。

## 参考文献 ##

[ranong项目总结-HttpClient-RetryHandler重试（一）][ranong_-HttpClient-RetryHandler]

[ranong_-HttpClient-RetryHandler]: http://blog.csdn.net/minicto/article/details/56677420