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From "Boyle Owen" <Owen.Bo...@swx.com>
Subject RE: [users@httpd] Updated apache modules load immediately?
Date Mon, 22 Dec 2003 13:45:52 GMT
> -----Original Message-----
> From: Josh Wyatt [mailto:Josh.Wyatt@hcssystems.com]
> 
> We're running Apache 1.3.19 (from Oracle).  It's configured 
> to dynamically load modules.
> 
> We updated the mod_ssl module, and apache immediately hung, 
> without being restarted or touched in any other way.
> 
> Is this behavior documented anywhere?  It seems a little 
> risque' that apache would go bottoms up when a loadable module 
> is updated in the filesystem and apache is not restarted.

It is perhaps a bit surprising - I was certainly suprised when it
happened to me. However, it should not be unexepected if you think
through what happens with dynamically loaded modules; the httpd binary
you have in apache/bin is a base version. When it starts up, it loads
the required modules - this happens *every time* a new daemon is
spawned. So, although in "human-time" apache seemed to hang immediately,
in "machine-time", the daemons which were already live when you saved
the new module continued to function normally (they had the old module
in memory). Then, as they were reaped after reaching MaxRequests, any
new daemon which was spawned by the parent process tried to load the new
module. Since this had not been compiled against the existing httpd, all
the address pointers were wrong and each new daemon seg-faulted as it
came up.

The lesson is that dynamically loading modules must only be used with
the httpd binary that they were compiled against. Alternatively, if you
want to upgrade a module, you have to recompile apache too.

Personally, every time I upgrade anything in the apache distro, I create
a new installation directory for it. I use codenames to differentiate
the builds so I have server_roots like /home/apache/versions/airdrie,
/home/apache/versions/brechin and so on. This keeps all packages
hermetically sealed from each other and makes it easy to roll-back. I
select the version from a global /home/apache/bin/apachectl which has
the line:

HTTPD=/home/apache/versions/${VERSION}/bin/httpd 

where $VERSION is set on the command-line.

Rgds,
Owen Boyle
Disclaimer: Any disclaimer attached to this message may be ignored. 

> 
> Thanks,
> Josh
> 
> 
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