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Re: CentOS & PostgreSQL help re: TIME_WAIT

From: Greg Stark <gsstark(at)mit(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Reggie Euser <reggie(at)busicast(dot)com>, pgsql-admin(at)postgresql(dot)org
Subject: Re: CentOS & PostgreSQL help re: TIME_WAIT
Date: 2010-01-29 18:30:18
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Lists: pgsql-admin
On Thu, Jan 28, 2010 at 8:55 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> In general, sockets sitting a long time in TIME_WAIT would be a network
> problem.  That state means the user process already closed the socket
> and the network stack is waiting for the other end to acknowledge
> connection closure.

I think you're describing FIN_WAIT. TIME_WAIT is after the finack has
been sent and the connection is well and truly dead. The same
host/port pair can't be reused for 2*msl in case the finack needs to
be resent or a duplicate fin arrives.

Normally the server uses SO_LINGER and skips TIME_WAIT so it can
listen on the same port immediately and accept more connections.  So
only the client enters TIME_WAIT and its for some random high-numbered
port that the OS won't hand out until it expires.

If you're seeing the postgres *server* with sockets in TIME_WAIT state
for port 5432 or whatever your postgres port is then I think that's a
bug and you should report it in more detail. please send the output of
netstat -an or whatever data you have showing the problem.

If you're seeing the web server's outgoing ports in TIME_WAIT state
then I think that's normal and shouldn't be causing you problems.


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Subject: Re: CentOS & PostgreSQL help re: TIME_WAIT
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