restTemplate实现ClientHttpRequestInterceptor，报错org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool

代码如下：

@Configuration
public class HttpConfig {

    private static final Integer RETRY_COUNT = 3;

    @Bean
    public RestTemplate restTemplate() {
        //设置超时时间
        HttpComponentsClientHttpRequestFactory httpRequestFactory = new HttpComponentsClientHttpRequestFactory();
        httpRequestFactory.setConnectionRequestTimeout(10000);
        /** 连接超时参数 ConnectTimeout，让用户配置建连阶段的最长等待时间 **/
        httpRequestFactory.setConnectTimeout(10000);
        /** 读取超时参数 ReadTimeout，用来控制从 Socket 上读取数据的最长等待时间 5s**/
        httpRequestFactory.setReadTimeout(5000);
        RestTemplate restTemplate = new RestTemplate(httpRequestFactory);
        //设置UTF-8 编码
        restTemplate.getMessageConverters().set(1, new StringHttpMessageConverter(StandardCharsets.UTF_8));
        restTemplate.getInterceptors().add(new LoggingClientHttpRequestInterceptor());
        return restTemplate;
    }

    @Slf4j
    public static class LoggingClientHttpRequestInterceptor implements ClientHttpRequestInterceptor {

        @Override
        public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
            /**
             * {@link InterceptingClientHttpRequest.InterceptingRequestExecution#execute(HttpRequest, byte[])} 当拦截器链处理完，开始执行真正请求
             */
            int retryCount = 1;
            ClientHttpResponse response = null;
            while (retryCount <= RETRY_COUNT) {
                try {
                    long start = System.currentTimeMillis();
                    response = execution.execute(request, body);
                    log.info("[method:{}] [url:{}] [reqBody:{}] [status:{}] [time:{}]", request.getMethod(), request.getURI(), new String(body, "UTF-8"), response.getStatusCode(), System.currentTimeMillis() - start);
                    if(response.getStatusCode().value() != HttpStatus.OK.value()){
                        throw new CommonApiException("[method:" + request.getMethod() +"]" +  "[url:"+ request.getURI() +"]"+"[status:"+response.getStatusCode()+"]"+"请求失败");
                    }
                    return response;
                } catch (Exception e) {
                
                    if (retryCount == RETRY_COUNT) {
                        throw new ResourceNotFoundException("[HttpConfig]重试异常：" + e);
                    }
                    log.info("准备进行重试：[url:{}]重试第{}次", request.getURI(), retryCount);
                }finally {
                    retryCount++;
                }

                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    log.warn("[HttpConfig] [Thread.sleep] 错误", e);
                }
            }
            return null;
        }
    }
}

主要是针对restTemplate调用的接口进行重试处理，重试3次。上线后意外报错，幸好及时发现，问题不大。
分析产生报错的原因：调用的外系统接口调用404，本系统无法关闭连接资源，导致线程池超时，报错如下：

解决：报错后将连接资源关闭即可，即在catch中加入以下代码：

if (response != null) {
    response.close();
}

finish！