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From "Costas Stergiou" <cst...@aias.gr>
Subject [REPOST]: mod_jk: ajp13: cpu load problem with apache
Date Thu, 16 May 2002 05:14:06 GMT
Hi all,
nobody seemed to reply anything on this matter. Looking through
the code myself I came to some conclusions but actually the one(s)
who really know the code should take a look.

PLEASE, take another look at this problem. Actually, the Apache-Tomcat
integration is useless with such a problem (and there are no alternatives
if you want load balancing...). I know that others have reported similar
issues.

Any help???

Thanks,
Costas

> Hi Costin,
> continuing on the problem:
>
> 1. I downloaded the latest code from CVS and compiled mod_jk.
> 2. Run apache with it and used gdb to get a stack trace upon
> the problem. Here is the gdb output:
>
> [helium]/#gdb httpd 24550
> GNU gdb 5.0-aix43-010414
> Copyright 2000 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you
are
> welcome to change it and/or distribute copies of it under certain
> conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for
details.
> This GDB was configured as "powerpc-ibm-aix4.3.3.0"...httpd: No such file
or
> dir
> ectory.
>
> //24550: No such file or directory.
> Attaching to process 24550
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> (no debugging symbols found)...(no debugging symbols found)...
> ---Type <return> to continue, or q <return> to quit---
> [Switching to Thread 1]
> 0x20070e9c in jk_tcp_socket_recvfull ()
> (gdb) bt
> #0  0x20070e9c in jk_tcp_socket_recvfull ()
> #1  0x2006b700 in ajp_connection_tcp_get_message ()
> #2  0x200694c0 in ajp_get_reply ()
> #3  0x20069344 in ajp_service ()
> #4  0x200744c8 in jk_handler ()
> #5  0x10020900 in ap_invoke_handler ()
> #6  0x10044c30 in process_request_internal ()
> #7  0x10045db4 in ap_process_request ()
> #8  0x10002a50 in child_main ()
> #9  0x1000244c in make_child ()
> #10 0x10002140 in perform_idle_server_maintenance ()
> #11 0x10001aec in standalone_main ()
> #12 0x10001390 in main ()
> #13 0x100001dc in __start ()
> (gdb) quit
> A debugging session is active.
> Do you still want to close the debugger?(y or n) y
> Detaching from program: , process 24550
>
> The only way to stop the above is either by restarting apache or
> killing the runaway apche process. gdb reports the same until I kill
> the process (never gets out of that process).
> Also, I must note that at the same time the jvm tomcat process also
> consumes a lot of CPU untill I kill the httpd process.
> Also, I use tomcat 4.0.3 with the compiled java mod_jk libs that
> come with the distribution.
>
> I hope that you can give some feedback on the above.
> Also, I think that the above problem is occurring when I press
> the stop button on my browser while I have made a 'big' request (one
> that brings back a 'big' html page).
>
> Any help is greatly welcome,
> Thanks,
> Costas
>
>
>
> ----- Original Message -----
> From: <costinm@covalent.net>
> To: "Tomcat Users List" <tomcat-user@jakarta.apache.org>
> Sent: Thursday, May 02, 2002 7:57 PM
> Subject: Re: Re: mod_jk: ajp13: cpu load problem with apache
>
>
> > On Thu, 2 May 2002 csterg@aias.gr wrote:
> >
> > > First of all thank you for your interest.
> > > I will download the latest code and try this out. I do have the debug
> mode
> > > enabled so I will sent you any errors (although I have not noticed
> anything
> > > special).
> > > I don't think though that I can reproduce the problem myself.
> > > About the gdb, I have no experience of how to attach to the process
but
> I will
> > > do my best to find a colleague that does.
> >
> > Short course on gdb:
> >
> > ps -aux |grep httpd
> > ( or ps -fea )
> >
> > Find the PID of the process that takes all the CPU, then
> >
> > gdb httpd PID
> > and inside do a 'bt' ( backtrace ), it'll generate a stacktrace
> > we can use.
> >
> >
> > Costin
> >
> > > Thanks,
> > > Costas
> > > >
> > > > Can you try the CVS head, and see if it still happens ?
> > > > If so, can you give us more details that would allow to
> > > > reproduce it ?
> > > >
> > > > Messages like 'it doesn't work for me, you figure out why'
> > > > are not very helpfull.
> > > >
> > > > At least enable the debug messages, let it run until it
> > > > hungs, then maybe trim the log and send the last entries.
> > > > Or use gdb to attach to the problem process and do a
> > > > stack trace.
> > > >
> > > > Costin
> > > >
> > > > On Wed, 1 May 2002, Costas Stergiou wrote:
> > > >
> > > > > Hi,
> > > > > I have an installation of Apache 1.3.19 + Tomcat 4.0.3
> > > > > on a aix4.3 machine with IBM JDK 1.3.0. I have two tomcat
> > > > > engines and I use the lb worker of mod_jk to balance user
> > > > > request to these two engines.
> > > > >
> > > > > The problem is that some httpd processes seem to go
> > > > > into some cpu performance tasks and start consuming all
> > > > > the cpu of the machine (2processors, 2GB mem). After
> > > > > some time almost all available CPU is consumed by the
> > > > > apache processes. If I kill the child processes that cause
> > > > > the problem, the load falls back to normal. At the same time,
> > > > > I notice that I have excessive CPU usage in one of the
> > > > > tomcat instances.
> > > > >
> > > > > The problem keeps recurring all the time (almost every hour).
> > > > > I read in the mail-archives about similar problems but I didn't
> > > > > find a good answer.
> > > > >
> > > > > The version of mod_jk is the one in
> jakarta-tomcat-connectors-4.0.2.01
> > > > > I compiled the source on the same machine (aix).
> > > > >
> > > > > I have to say that I have noticed similar problems on many more
> > > > > apache installations that have similar installations (apache, lb
+
> > > > > 2 or more tomcat engines) with older versions of mod_jk and
tomcat.
> > > > >
> > > > > Actually, the above problem makes the lb worker unusable since
> > > > > I cannot trust the setup in my production environment.
> > > > >
> > > > > Please, any idea or patches or whatever will be very helpful.
> > > > > Thanks very much for any ideas,
> > > > > Costas
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > > --
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