目前的项目接口都是http，因此在项目中使用apache httpclient进行数据传输、访问。
| 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），在这里我列举出我找到的retry方案，有些成功有些不成功。 我是用的httpclient版本是 在httpclient版本 |
StandardHttpRequestRetryHandler
这种方案没有通过，StandardHttpRequestRetryHandler实际上是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，如下，是我定义的httpclient pool
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;} 如下是我的测试代码
@Testpublic 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、后台超时等情况的时候不能进行retry，因此放弃了此方案。
DefaultHttpRequestRetryHandler
这种方案没有测试通过，和上面的StandardHttpRequestRetryHandler类似，它提供了一种默认的retry方案，并没有像StandardHttpRequestRetryHandler一样约定接口必须是冥等的，如下，是我定义的httpclient pool
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;} 如下是我的测试代码
@Testpublic 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); }} 依然没有达到希望的效果。
HttpRequestRetryHandler
可以实现，但是不够完美。在有这么一段，如下，
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，可以根据异常自定义retry机制以及重试次数，并且可以拿到返回信息，如下，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;} 如下是我的测试代码
@Testpublic 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，可以实现retry，并且可以根据我的需求进行retry，如：retry count，但是就不能控制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
可以实现，满足需求，这具有HttpRequestRetryHandler的所有有点，并且可以自定义retry时间的间隔，如下，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;} 如下是我的测试代码
@Testpublic 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); }}