如果主机脱机，请重试Java RestTemplate HTTP请求 [英] Retry java RestTemplate HTTP request if host offline

问题描述

我正在使用spring RestTemplate来调用REST API.该API可能非常慢，甚至离线.我的应用程序通过依次发送数千个请求来构建缓存.响应也可能非常慢，因为它们包含大量数据.

Hi I'm using the spring RestTemplate for calling a REST API. The API can be very slow or even offline. My application is building the cache by sending thousands of requests one after the other. The responses can be very slow too, because they contains a lot of data.

我已经将超时时间增加到120秒.现在的问题是该API可以脱机，并且出现org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool异常.

I have already increased the Timeout to 120 seconds. My problem now it that the API can be offline and I get a org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool exception.

在API离线的情况下，应用程序应等待并重试，直到API再次在线.

In the case when the API ist offline, the application should wait and try again until the API is online again.

我可以直接在RestTemplate中实现此目标而无需自己构建异常循环吗?

Can I achieve this in RestTemplate out of the box without building exception-loops on my own?

谢谢！

推荐答案

我遇到了同样的情况，并通过谷歌搜索找到了解决方案.给出答案，希望对其他人有所帮助.您可以为每次尝试设置最大尝试次数和时间间隔.

I had same situation and done some googling found the solution. Giving answer in hope it help someone else. You can set max try and time interval for each try.

@Bean
  public RetryTemplate retryTemplate() {

    int maxAttempt = Integer.parseInt(env.getProperty("maxAttempt"));
    int retryTimeInterval = Integer.parseInt(env.getProperty("retryTimeInterval"));

    SimpleRetryPolicy retryPolicy = new SimpleRetryPolicy();
    retryPolicy.setMaxAttempts(maxAttempt);

    FixedBackOffPolicy backOffPolicy = new FixedBackOffPolicy();
    backOffPolicy.setBackOffPeriod(retryTimeInterval); // 1.5 seconds

    RetryTemplate template = new RetryTemplate();
    template.setRetryPolicy(retryPolicy);
    template.setBackOffPolicy(backOffPolicy);

    return template;
  }

我想执行的休息服务在下面.

And my rest service that i want to execute is below.

retryTemplate.execute(context -> {
        System.out.println("inside retry method");
        ResponseEntity<?> requestData = RestTemplateProvider.getInstance().postAsNewRequest(bundle, ServiceResponse.class, serivceURL,
                CommonUtils.getHeader("APP_Name"));

        _LOGGER.info("Response ..."+ requestData);
            throw new IllegalStateException("Something went wrong");
        });

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