Apache HttpClient：如何通过服务器的保持活动时间自动关闭连接？

Question

Apache HttpClient 4.3b2, HttpCore 4.3.

I use PoolingHttpClientConnectionManager to manage 5 connections concurrently:

PoolingHttpClientConnectionManager connectionManager;
HttpClient httpclient;
connectionManager = new PoolingHttpClientConnectionManager();
connectionManager.setDefaultMaxPerRoute(5);
httpclient = HttpClientBuilder.create().setConnectionManager(connectionManager).build();

Server have 5 seconds keep-alive time. When server initiate close connection process it is staying in FIN_WAIT2 state until I'll execute connectionManager.shutdown() or connectionManager.closeExpiredConnections() or connectionManager.closeIdleConnections(5, TimeUnit.SECONDS) manually. Server waits FIN package. How can I automatically close connections on client side after server start closing process?

When I do requests from Chrome browser, server stay in TIME_WAIT state when it try to close connection by keep-alive (FIN_WAIT2 state changes very quickly). How can I get the same behavior with Apache HttpClient?

Answer 1

This problem is explained in details in HttpClient tutorial

One of the major shortcomings of the classic blocking I/O model is that the network socket can react to I/O events only when blocked in an I/O operation. When a connection is released back to the manager, it can be kept alive however it is unable to monitor the status of the socket and react to any I/O events. If the connection gets closed on the server side, the client side connection is unable to detect the change in the connection state (and react appropriately by closing the socket on its end).

If you want expired connections to get pro-actively evicted from the connection pool there is no way around running an additional thread enforcing a connection eviction policy that suits your application.

Answer 2

In PoolingHttpClientConnectionManager class there is a method setValidateAfterInactivity that sets period of connection inactivity in milliseconds. If this period has been exceeded connection pool revalidates connection before passing it to HttpClient. This method is available since v.4.4. In prior versions RequestConfig.Builder.setStaleConnectionCheckEnabled method could have been used.

Answer 3

I found this question multiple times while working on an Apache HttpClient 5 based client implementation to figure out whether a idle http connection monitor is still required.

Apparently, since Apache HttpClient 4.4, there is org.apache.hc.client5.http.impl.IdleConnectionEvictor which does exactly the thing described in HttpClient tutorial (which isn't mentioned in the tutorial).

Thought it might be useful to be aware of this for others as well.