总结-HttpClient-RetryHandler重试

时间 2019-11-06

标签总结 httpclient retryhandler 重试栏目系统网络繁體版

原文原文链接

目前的项目接口都是http，所以在Java项目中使用apache httpclient进行数据传输、访问。html

目前程序中涉及到须要callback操做，product须要被动的接收consume的处理状态，为了最大程度的可以callback成功所以consume在http调用出现问题（如：服务不可用、异常、超时）状况下须要进行重试（retry request），在这里我列举出我找到的retry方案，有些成功有些不成功。java

我是用的httpclient版本是4.5.2。关于retry功能我在网上也找了很多的资料，可是都不是我对应的httpclient版本，大可能是过期的。apache

在httpclient版本4.5.2提供了如下几种retry方案：ide

StandardHttpRequestRetryHandler

这种方案没有测试经过，StandardHttpRequestRetryHandler其实是DefaultHttpRequestRetryHandler的子类，这是官方提供的一个标准的retry方案，为了保证幂等性约定resetful接口必须是GET, HEAD, PUT, DELETE, OPTIONS, and TRACE中的一种，以下，是我定义的httpclient pool测试

public static CloseableHttpClient getHttpClient() {
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal(MAX_TOTAL);
    cm.setDefaultMaxPerRoute(MAX_PERROUTE);
    CloseableHttpClient httpClient = HttpClients
        .custom()
        .setRetryHandler(new StandardHttpRequestRetryHandler())
        .setConnectionManager(cm)
        .build();
    return httpClient;
}

以下是个人测试代码ui

@Test
public void test6(){
    HttpPost httpPost=new HttpPost("http://127.0.0.1:8080/testjobs1");
    try {
        rsp=httpClient.execute(httpPost);
        log.info(">> {}",rsp.getStatusLine().getStatusCode());
    } catch (Exception e) {
        log.error(e.getMessage(),e);
    }finally{
        HttpUtil.close(rsp);
    }
}

运行测试，当url错误、后台报错、后台超时等状况的时候不能进行retry，所以放弃了此方案。url

DefaultHttpRequestRetryHandler

这种方案没有测试经过，和上面的StandardHttpRequestRetryHandler相似，它提供了一种默认的retry方案，并无像StandardHttpRequestRetryHandler同样约定接口必须是冥等的，以下，是我定义的httpclient poolspa

public static CloseableHttpClient getHttpClient() {
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal(MAX_TOTAL);
    cm.setDefaultMaxPerRoute(MAX_PERROUTE);
    CloseableHttpClient httpClient = HttpClients
        .custom()
        .setRetryHandler(new DefaultHttpRequestRetryHandler())
        .setConnectionManager(cm)
        .build();
    return httpClient;
}

以下是个人测试代码.net

@Test
public void test6(){
    HttpPost httpPost=new HttpPost("http://127.0.0.1:8080/testjobs1");
    try {
        rsp=httpClient.execute(httpPost);
        log.info(">> {}",rsp.getStatusLine().getStatusCode());
    } catch (Exception e) {
        log.error(e.getMessage(),e);
    }finally{
        HttpUtil.close(rsp);
    }
}

依然没有达到但愿的效果。code

HttpRequestRetryHandler

能够实现，可是不够完美。在官方文档有这么一段，以下，

HttpRequestRetryHandler myRetryHandler = new HttpRequestRetryHandler() {
    public boolean retryRequest(
        IOException exception,
        int executionCount,
        HttpContext context) {
        if (executionCount >= 5) {
            // Do not retry if over max retry count
            return false;
        }
        if (exception instanceof InterruptedIOException) {
            // Timeout
            return false;
        }
        if (exception instanceof UnknownHostException) {
            // Unknown host
            return false;
        }
        if (exception instanceof ConnectTimeoutException) {
            // Connection refused
            return false;
        }
        if (exception instanceof SSLException) {
            // SSL handshake exception
            return false;
        }
        HttpClientContext clientContext = HttpClientContext.adapt(context);
        HttpRequest request = clientContext.getRequest();
        boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
        if (idempotent) {
            // Retry if the request is considered idempotent
            return true;
        }
        return false;
    }
};
CloseableHttpClient httpclient = HttpClients.custom().setRetryHandler(myRetryHandler).build();

自定义retry实现，这比较灵活，能够根据异常自定义retry机制以及重试次数，而且能够拿到返回信息，以下，是我定义的httpclient pool

public static CloseableHttpClient getHttpClient() {
    HttpRequestRetryHandler retryHandler = new HttpRequestRetryHandler() {
        public boolean retryRequest(
            IOException exception,
            int executionCount,
            HttpContext context) {
            if (executionCount >= 5) {
                // Do not retry if over max retry count
                return false;
            }
            if (exception instanceof InterruptedIOException) {
                // Timeout
                return false;
            }
            if (exception instanceof UnknownHostException) {
                // Unknown host
                return false;
            }
            if (exception instanceof ConnectTimeoutException) {
                // Connection refused
                return false;
            }
            if (exception instanceof SSLException) {
                // SSL handshake exception
                return false;
            }
            HttpClientContext clientContext = HttpClientContext.adapt(context);
            HttpRequest request = clientContext.getRequest();
            boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
            if (idempotent) {
                // Retry if the request is considered idempotent
                return true;
            }
            return false;
        }
    };
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal(MAX_TOTAL);
    cm.setDefaultMaxPerRoute(MAX_PERROUTE);
    CloseableHttpClient httpClient = HttpClients
        .custom()
        .setRetryHandler(retryHandler)
        .setConnectionManager(cm)
        .build();
    return httpClient;
}

以下是个人测试代码

@Test
public void test6(){
    HttpPost httpPost=new HttpPost("http://127.0.0.1:8080/testjobs1");
    try {
        rsp=httpClient.execute(httpPost);
        log.info(">> {}",rsp.getStatusLine().getStatusCode());
    } catch (Exception e) {
        log.error(e.getMessage(),e);
    }finally{
        HttpUtil.close(rsp);
    }
}

这种方案，能够实现retry，而且能够根据个人需求进行retry，如：retry count，可是就不能控制retry时间的间隔，也只好放弃了，继续寻找找到了下面这个ServiceUnavailableRetryStrategy。

ServiceUnavailableRetryStrategy

能够实现，知足需求，这具备HttpRequestRetryHandler的全部有点，而且能够自定义retry时间的间隔，以下，是我定义的httpclient pool，

public static CloseableHttpClient getHttpClient() {
    ServiceUnavailableRetryStrategy serviceUnavailableRetryStrategy = new ServiceUnavailableRetryStrategy() {
        /**
         * retry逻辑
         */
        @Override
        public boolean retryRequest(HttpResponse response, int executionCount, HttpContext context) {
            if (executionCount <= 3)
                return true;
            else
                return false;
        }
        /**
         * retry间隔时间
         */
        @Override
        public long getRetryInterval() {
            return 2000;
        }
    };
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal(MAX_TOTAL);
    cm.setDefaultMaxPerRoute(MAX_PERROUTE);
    CloseableHttpClient httpClient = HttpClients.custom().setRetryHandler(new DefaultHttpRequestRetryHandler())
        .setConnectionManager(cm).build();
    return httpClient;
}

以下是个人测试代码

@Test
public void test6(){
    HttpPost httpPost=new HttpPost("http://127.0.0.1:8080/testjobs1");
    try {
        rsp=httpClient.execute(httpPost);
        log.info(">> {}",rsp.getStatusLine().getStatusCode());
    } catch (Exception e) {
        log.error(e.getMessage(),e);
    }finally{
        HttpUtil.close(rsp);
}
}