Thread

1. RE: Hung backends

   Schmidt, Peter <peter.schmidt@prismedia.com> — 2000-11-24T17:02:42Z

   It turned out the Java VM was still running on the clients, keeping TCP
   connections open (exactly as you suggested). When the VM process is killed
   all backends are cleaned up.
   Thanks,
   Peter
   
   
   -----Original Message-----
   From: Tom Lane [mailto:tgl@sss.pgh.pa.us]
   Sent: Thursday, November 23, 2000 9:35 AM
   To: Schmidt, Peter
   Cc: 'pgsql-general@postgresql.org'
   Subject: Re: [GENERAL] Hung backends 
   
   
   "Schmidt, Peter" <peter.schmidt@prismedia.com> writes:
   > The java frontend I'm using to test this scenario makes multiple
   connections
   > and crashes(unhandled exception) before disconnecting. This appears to
   leave
   > one "postgres" proccess for each connection. Can anyone point me in the
   > right direction?
   > SELECT version(); ->  PostgreSQL 7.0.2 on i386-unknown-freebsdelf4.0
   
   Hm.  I'd definitely recommend updating to 7.0.3 if you are using
   unreliable clients, because 7.0.2 forgets to run its transaction-abort
   routine if the client disconnects mid-transaction, with various
   annoying consequences.  However, that wouldn't lead to the
   above-described symptom.
   
   It looks like the backends don't know that their clients have gone away,
   which would suggest that the kernel is failing to deliver an EOF
   indication on the socket connection.  Are you using TCP connections,
   or Unix sockets?  Is there some other process that could be holding the
   client end of the connection open?
   
   			regards, tom lane
   

2. Re: Hung backends

   Tom Lane <tgl@sss.pgh.pa.us> — 2000-11-24T17:22:12Z

   "Schmidt, Peter" <peter.schmidt@prismedia.com> writes:
   > It turned out the Java VM was still running on the clients, keeping TCP
   > connections open (exactly as you suggested).
   
   Hmm, so the VM forgets to close connections belonging to a crashed
   Java thread?  Seems like a severe deficiency in the VM to me...
   
   			regards, tom lane
   
   

3. Re: Hung backends

   Joseph Shraibman <jks@selectacast.net> — 2000-11-27T23:53:02Z

   Tom Lane wrote:
   > 
   > "Schmidt, Peter" <peter.schmidt@prismedia.com> writes:
   > > It turned out the Java VM was still running on the clients, keeping TCP
   > > connections open (exactly as you suggested).
   > 
   > Hmm, so the VM forgets to close connections belonging to a crashed
   > Java thread?  Seems like a severe deficiency in the VM to me...
   > 
   >                         regards, tom lane
   
   There is no such thing as a crashed java thread.  It either terminated
   or is still running.  You are supposed to explictly close your
   connections to the db in java.  If you don't you will have to wait until
   the Connection object is garbage collected for it to be closed.  If your
   java app is sitting around not doing much then it might never get around
   to calling the garbage collector.
   
   Bottom line:
   1) expliclty close connections yourself
   2) Call System.gc() from time to time if you need to.
   
   -- 
   Joseph Shraibman
   jks@selectacast.net
   Increase signal to noise ratio.  http://www.targabot.com