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Posted to modperl@perl.apache.org by Joshua Chamas <jo...@chamas.com> on 2001/04/05 07:29:51 UTC
Re: Apache::ASP -- Corruption of statedir files/truncation of
methodnames
Carl Lipo wrote:
>
> I've just started having problems with asp state files for Apache::ASP
> 2.09 becoming corrupted during use. My application will work just fine but
> at somepoint the session asp state files get corrupted and only deleting
> them allows the application to continue working. Oddly, this occurs on two
> different servers so the problem does not appear to be machine specific.
>
> The symptom of the problem is that application errors are returned
> from the asp code execution that look something like this:
>
> Uncaught exception from user code:
> Can't locate object method 'Quer' via package
> "Apache::ASP::Request'; at (eval 263) <a href=#167>l
> ine 167</a>. INAP::NEIS::_usr_local_applprod_infosource_apps_netcfg_viewNodes_htmxINL() called
> at /usr/local/lib/site_perl/Apache/
> ASP.pm line 1504
>
Generally problems of this nature, where even perl data seems
to be corrupted, seem to be from buffer overrun type issues
that normally result in segfaults. Looking at your config,
I would suspect the culprit to be use of DB_File on your
StateDir, where /usr/local/etc/infosource/apps/netcfg/state-dir
may be mounted over NFS. NFS typically does not support the
flock() style locking that Apache::ASP uses to protect DB_File
from corruption.
If you are & must use NFS, don't use DB_File, use the default
SDBM_File, which does not corrupt as easily. If you need to
get past the 1000 byte limit, then you might use
MLDBM::Sync::SDBM_File which I developed just for this purpose.
I need to add config support for this still to Apache::ASP though.
If you can switch to a CIFS/or samba mounted file system, do
this, as this supports flock() semantics.
If StateDir is mounted locally, then possibly there is a bug in
Apache::ASP StateDB locking, but this is less likely the case
and we might look at other types of buffer overrun issues that
might corrupt perl data structures. If your modperl httpd is compiled
DSO, compile it static, as I have seen no end of odd errors with
the DSO config from time to time.
Also, DBD::Oracle and long values with CLOBs/BLOBs can create
another type of buffer overrun, which is supposedly on OCI bug,
though you didn't mention use of Oracle this is an odd bug that
stung me recently.
If you give up on trying to find this bug, which seems to be
related to StateDB corruption, you may create $Application &
$Session objects with Apache::Session in the global.asa Script_OnStart,
which would at least eliminate the StateDB issue.
-- Josh
_________________________________________________________________
Joshua Chamas Chamas Enterprises Inc.
NodeWorks >> free web link monitoring Huntington Beach, CA USA
http://www.nodeworks.com 1-714-625-4051
Re: Apache::ASP -- Corruption of statedir files/truncation of
methodnames
Posted by Carl Lipo <ca...@internap.com>.
The statedir is local so it doesnt seem to be an NFS issue. There
definitely seems to be a corruption of the StateDir files: here is a error
that crops up in our error log.
[Thu Apr 5 08:09:07 2001] [notice] child pid 11555 exit signal
Segmentation fault (11)
Use of uninitialized value at /usr/lib/perl5/MLDBM.pm line 161 (#1)
(W) An undefined value was used as if it were already defined. It was
interpreted as a "" or a 0, but maybe it was a mistake. To suppress
this warning assign an initial value to your variables.
Unauthorized use, disclosure, or distribution of information within
this message is prohibited.
On Wed, 4 Apr 2001, Joshua Chamas wrote:
> Carl Lipo wrote:
> >
> > I've just started having problems with asp state files for Apache::ASP
> > 2.09 becoming corrupted during use. My application will work just fine but
> > at somepoint the session asp state files get corrupted and only deleting
> > them allows the application to continue working. Oddly, this occurs on two
> > different servers so the problem does not appear to be machine specific.
> >
> > The symptom of the problem is that application errors are returned
> > from the asp code execution that look something like this:
> >
> > Uncaught exception from user code:
> > Can't locate object method 'Quer' via package
> > "Apache::ASP::Request'; at (eval 263) <a href=#167>l
> > ine 167</a>. INAP::NEIS::_usr_local_applprod_infosource_apps_netcfg_viewNodes_htmxINL() called
> > at /usr/local/lib/site_perl/Apache/
> > ASP.pm line 1504
> >
>
> Generally problems of this nature, where even perl data seems
> to be corrupted, seem to be from buffer overrun type issues
> that normally result in segfaults. Looking at your config,
> I would suspect the culprit to be use of DB_File on your
> StateDir, where /usr/local/etc/infosource/apps/netcfg/state-dir
> may be mounted over NFS. NFS typically does not support the
> flock() style locking that Apache::ASP uses to protect DB_File
> from corruption.
>
> If you are & must use NFS, don't use DB_File, use the default
> SDBM_File, which does not corrupt as easily. If you need to
> get past the 1000 byte limit, then you might use
> MLDBM::Sync::SDBM_File which I developed just for this purpose.
> I need to add config support for this still to Apache::ASP though.
> If you can switch to a CIFS/or samba mounted file system, do
> this, as this supports flock() semantics.
>
> If StateDir is mounted locally, then possibly there is a bug in
> Apache::ASP StateDB locking, but this is less likely the case
> and we might look at other types of buffer overrun issues that
> might corrupt perl data structures. If your modperl httpd is compiled
> DSO, compile it static, as I have seen no end of odd errors with
> the DSO config from time to time.
>
> Also, DBD::Oracle and long values with CLOBs/BLOBs can create
> another type of buffer overrun, which is supposedly on OCI bug,
> though you didn't mention use of Oracle this is an odd bug that
> stung me recently.
>
> If you give up on trying to find this bug, which seems to be
> related to StateDB corruption, you may create $Application &
> $Session objects with Apache::Session in the global.asa Script_OnStart,
> which would at least eliminate the StateDB issue.
>
> -- Josh
>
> _________________________________________________________________
> Joshua Chamas Chamas Enterprises Inc.
> NodeWorks >> free web link monitoring Huntington Beach, CA USA
> http://www.nodeworks.com 1-714-625-4051
>
>