问题：我间歇性地收到此错误消息。我使用的是httpclient-4.5.2和PoolingClientConnectionManager
我尝试了什么：
由于某些帖子暗示这可能是由于陈旧 连接，我尝试使用
从连接管理器清理它connectionManager.closeExpiredConnections();
connectionManager.closeIdleConnections( idleTime, TimeUnit.MINUTES );
建议使用here
我也试过HttpConnectionParams.setStaleCheckingEnabled（ reqParams，true）;
，如doc
我启用了wirelogs，但没有什么异常：
2017-09-25T02:26:36.109495-07:00 tomcat: [PoolingClientConnectionManager] DEBUG: Connection request: [route: {s}->https://host:443][total kept alive: 3; route allocated: 4 of 20; total allocated: 7 of 800]
2017-09-25T02:26:36.109598-07:00 tomcat: [PoolingClientConnectionManager] DEBUG: Connection leased: [id: 150][route: {s}->https://host:443][total kept alive: 2; route allocated: 4 of 20; total allocated: 7 of 800]
2017-09-25T02:26:36.111038-07:00 tomcat: [DefaultClientConnection] DEBUG: Sending request: GET /api/v1/foo HTTP/1.1
2017-09-25T02:26:36.111152-07:00 tomcat: [Wire] DEBUG: >> "GET /api/v1/foo HTTP/1.1[\r][\n]"
2017-09-25T02:26:36.111282-07:00 tomcat: [Wire] DEBUG: >> "Accept: application/json[\r][\n]"
2017-09-25T02:26:36.111373-07:00 tomcat: [Wire] DEBUG: >> "Cookie: JSESSIONID=432jnfjwnfkjw3[\r][\n]"
2017-09-25T02:26:36.111459-07:00 tomcat: [Wire] DEBUG: >> "Accept-Encoding: gzip,deflate[\r][\n]"
2017-09-25T02:26:36.111541-07:00 tomcat: [Wire] DEBUG: >> "Content-Length: 0[\r][\n]"
2017-09-25T02:26:36.111635-07:00 tomcat: [Wire] DEBUG: >> "Host: host:443[\r][\n]"
2017-09-25T02:26:36.111712-07:00 tomcat: [Wire] DEBUG: >> "Connection: Keep-Alive[\r][\n]"
2017-09-25T02:26:36.111789-07:00 tomcat: [Wire] DEBUG: >> "[\r][\n]"
2017-09-25T02:26:36.112470-07:00 tomcat: [DefaultClientConnection] DEBUG: Connection 0.0.0.0:57992<->10.2.1.1:443 closed
2017-09-25T02:26:36.112633-07:00 tomcat: [DefaultClientConnection] DEBUG: Connection 0.0.0.0:57992<->10.2.1.1:443 closed
2017-09-25T02:26:36.112757-07:00 tomcat: [DefaultRequestDirector] INFO : I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://host:443: The target server failed to respond
即使进行了上述更改，我仍然会看到NoHttpResponse错误。我还可以尝试找出根本原因并修复它？