topic Re: CLOSE_WAIT issues in Operating System - HP-UX

CLOSE_WAIT issues

Joydeep_1 — Thu, 05 Dec 2002 09:27:41 GMT

Hi,

I am facing CLOSE_WAIT issues in 4 servers. Two of them in 11i environment & rest two are in 11 environment.

We have configured two WebLogic Cluster & configured our application.

But when user starts to access that application thru http port after some time there are lots of CLOSE_WAIT spawned which hang that port & made inaccessible of that application. Sometimes we have seen there are more than 2000 CLOSE_WAIT value.

I have checked our servers Patch level by HP & they have certified those environments.

I tuned some networking parameters (tcp_keepalive_detached_interval,
tcp_fin_wait_2_timeout, tcp_time_wait_interval) & configured those parameters as 10 secs.

It did not help to get rid of CLOSE_WAIT.

Please advise me how I can get rid of this problem.

Re: CLOSE_WAIT issues

U.SivaKumar_2 — Thu, 05 Dec 2002 09:35:36 GMT

Hi,

Refer these threads

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0xa17985079106d71190050090279cd0f9,00.html

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x59af3a1c04ffd61190050090279cd0f9,00.html

regards,
U.SivaKumar

Re: CLOSE_WAIT issues

Stefan Farrelly — Thu, 05 Dec 2002 09:40:55 GMT

Take a look at this question, and in particular the .doc attachment on one reply which explains in a bit more detail FIN_WAIT and CLOSE_WAIT.

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x14eaf841489fd4118fef0090279cd0f9,00.html

Dont forget ndd changes dont take effect if you reboot unless you set them in /etc/rc.config.d/nddconf

Typically in my opinion this is an application issue. Either a remote connection has crashed or rebooted or not been closed properly (eg. a PC or a user who shuts it down without closing their applications). The only things you can do on the HP end are kill these connections using a script and ndd (script to do it on the link above) or set the timeouts low - which youve done, or find the users responsible, see what thyere doing, and clobber them if you can.

Re: CLOSE_WAIT issues

Joydeep_1 — Thu, 05 Dec 2002 10:13:50 GMT

Thanks to all whoever has replied.

I tried to clean all CLOSE_WAIT value by one script which I got from Shiva's URL.

But unfortunately it could not.

I set tcp_keepalive_interval parameter to 10 secs also. It did not help.

Is it Weblogic issue ? I am using Weblogic 6.1

Re: CLOSE_WAIT issues

U.SivaKumar_2 — Thu, 05 Dec 2002 10:21:08 GMT

Hi,

I understand that it is known problem in weblogic from weblogic newsgroup.

Some Fixex are also available
http://edocs.bea.com/wls/docs61/notes/bugfixes2.html

regards,
U.SivaKumar

Re: CLOSE_WAIT issues

rick jones — Fri, 06 Dec 2002 19:17:25 GMT

The CLOSE_WAIT state is the state a TCP connection enters when it has received and ACKnowledged a FIN from the remote and is now waiting for the local application to call close() or shutdown().

99 times out of 10, a connection "stuck" in CLOSE_WAIT means the application at that end has a bug - it is either ignoring, or forgetting when it was told that the remote has initiated a shutdown of the connection.

The other, much more rare case, is that this is an application that is using TCP to transfer data in one direction only. CLOSE_WAIT is a perfectly valid "send only" state for a TCP connection, assuming that the remote side, in FIN_WAIT_2, got there by doing a shutdown(SHUT_WR) and not a SHUT_RD or SHUT_RDWR or close().

This is why I am not terribly fond of the arbitrary fin_wait_2_timeout for dealing with FIN_WAIT_2. I much prefer to let the "normal" tcp_keepalive_detached_interval, which will deal with a different sort of client bug - when the client uses an abortive (RST instead of FIN) close of the TCP connection. That is a doubleplusungood thing to do, the RST is not retransmitted, and it can leave the server stuck in FIN_WAIT_2. The tcp_keepalive_detached_interval will deal with FIN_WAIT_2 on the server when the server calls close() - at that point it will send keepalives, and if the keepalives get no response, or elicit a RST from the remote, it will terminate the FIN_WAIT_2.

Do not mess with the tcp_time_wait_interval. It should stay at 60 seconds or more. It is only for connections in TIME_WAIT, and TIME_WAIT is an integral part of TCP's correctness heuristics. I also would not suggest a tcp_find_wait_2_timeout of 10 seconds - if you must use it, keep it at least as long as tcp_time_wait_interval.

I'd also probably not make tcp_keepalive_detached_interval a mere 10 seconds. The two minute default should suffice - again 99 times out of 10 :) and if you do need to make it shorter, again I'd not make it any shorter than tcp_time_wait_interval.