Req #64709 [Wfx]: Get a PHP stack trace on process signal
Edit report at https://bugs.php.net/bug.php?id=64709&edit=1
ID: 64709
Updated by: rasmus@php.net
Reported by: williama_lovaton at coomeva dot com dot co
Summary: Get a PHP stack trace on process signal
Status: Wont fix
Type: Feature/Change Request
Package: Performance problem
Operating System: Linux
PHP Version: Irrelevant
Block user comment: N
Private report: N
New Comment:
I put the link to the gdbinit right in my reply. That explanation should be all
you need.
Previous Comments:
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[2013-04-26 13:59:48] williama_lovaton at coomeva dot com dot co
Fair enough, I was thinking exactly the same that running as an Apache module PHP would not be in
charge of the signal handling and the result could be unexpected at best.
Is there some kind of documentation that explains in more detail what you are saying? I wonder
where can I get the .gdbinit you are referring to. The thing is that I am using PHP 5.3.3 as
packaged by Red Hat Enterprise Linux so I guess I can't use the one you linked in the comment.
Thanks a lot for your help.
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[2013-04-26 02:04:00] rasmus@php.net
Why not just attach gdb to the process and do a bt? I do that all the time. If
it is in an internal PHP function you will see zif_funcname where zif = zend
internal function. If it is in a userspace function it is slightly harder. You
need to install the .gdbinit gdb macros from https://raw.github.com/php/php-
src/master/.gdbinit in your home directory and you can then type zbacktrace and
you get the entire PHP call stack.
The problem with adding a signal handler is that PHP is often not a standalone
thing. It is embedded inside Apache or other mechanisms that own the signal
handling layer. Any signal we pick would conflict with something at the server
level and this is a rather low-level feature for developers who know what they
are doing anyway. If they know what they are doing they should be able to
navigate gdb.
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[2013-04-25 20:29:27] williama_lovaton at coomeva dot com dot co
Thanks for your comments. I'm using both tools (xdebug and XHProf), they are excellent but
xdebug has a big performance impact even if you are not using it and right now I can't afford
that on production, I use it in my development environment though. XHProf is enabled on production
and it is really great but as far as I know it can only show me the data after the fact.
The specific thing about this feature request is that I want to see where a given process is stuck
while it's still serving the request. For example, with gstack I can see the process is stuck
in the OCIExecute() function executing a query or in OCIStmtFetch() function fetching the data
(I'm using an Oracle database). But I can't see which PHP function, and hence the query,
is causing the slowness.
This have been asked before by other people under different scenarios:
http://stackoverflow.com/questions/14261821/get-a-stack-trace-of-a-hung-php-script
But there is no satisfying answer.
I was just wondering if this feature is at all doable.
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[2013-04-25 19:11:18] sixd@php.net
Also review XHProf & XHGui
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[2013-04-25 17:19:16] ab@php.net
With performance - what about profiling with xdebug or zend?
The other were for sure possible catching some signal. Though dunno yet if the same gdb
functionality is available on windows.
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