Sockets in CLOSE_WAIT from Jersey Client

Question

I am using Jersey 1.4, the ApacheHttpClient, and the Apache MultiThreadedHttpConnectionManager class to manage connections. For the HttpConnectionManager, I set staleCheckingEnabled to true, maxConnectionsPerHost to 1000 and maxTotalConnections to 1000. Everything else is default. We are running in Tomcat and making connections out to multiple external hosts using the Jersey client.

I have noticed that after after a short period of time I will begin to see sockets in a CLOSE_WAIT state that are associated with the Tomcat process. Some monitoring with tcpdump shows that the external hosts appear to be closing the connection after some time but it's not getting closed on our end. Usually there is some data in the socket read queue, often 24 bytes. The connections are using https and the data seems to be encrypted so I'm not sure what it is.

I have checked to be sure that the ClientRequest objects that get created are closed. The sockets in CLOSE_WAIT do seem to get recycled and we're not running out of any resources, at least at this time. I'm not sure what's happening on the external servers.

My question is, is this normal and should I be concerned?

Thanks,

John

Answer 1

This is likely to be a device such as the firewall or the remote server timing out the TCP session. You can analyze packet captures of HTTPS using Wireshark as described on their SSL page:

http://wiki.wireshark.org/SSL

The staleCheckingEnabled flag only issues the check when you go to actually use the connection so you aren't using network resources (TCP sessions) when they aren't needed.