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Apache resource agent broken in Debian lenny

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f.knauf at mmkf

Jul 19, 2008, 12:41 PM

Post #1 of 7 (553 views)
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Apache resource agent broken in Debian lenny

Hi,

If I should have written this to the Debian package maintainer, my bad,
but since there's a debian/ subdirectory in the source tree, I thought
this might interest you.

The latest apache2.2-common update in Debian lenny (2.2.9-5) breaks the
hearbeat ocf resource agent heuristics that determine what user to run
it as and where to put the pid file. The apache2.conf now sports

PidFile ${APACHE_PID_FILE}
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}

instead of the actual place and user/group ids, which are specified in
/etc/apache2/envvars like so:

export APACHE_RUN_USER=www-data
export APACHE_RUN_GROUP=www-data
export APACHE_PID_FILE=/var/run/apache2.pid

Since the resource agent basically greps the apache configuration for
these, it ends up using ${APACHE_FOO_BAR}, and since
/etc/apache2/envvars is never read, leaves them empty - which makes the
whole thing fail miserably.

In principle, the fix for this is trivial - the resource agent just has
to do something like

if [ -e /etc/apache2/envvars ]; then
. /etc/apache2/envvars
fi

before the action starts - this is what /etc/init.d/apache2 does.
However, I am unsure whether hardcoding it in this manner is the right
way to go - it might be prudent to make it a runtime variable like
OCF_RESKEY_configfile, only to be loaded if specified.

What do you think?

Regards,

Florian Knauf
_______________________________________________________
Linux-HA-Dev: Linux-HA-Dev[at]lists.linux-ha.org
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dejanmm at fastmail

Jul 20, 2008, 8:30 AM

Post #2 of 7 (526 views)
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Re: Apache resource agent broken in Debian lenny [In reply to]

Hi,

On Sat, Jul 19, 2008 at 09:41:29PM +0200, Florian Knauf wrote:
> Hi,
>
> If I should have written this to the Debian package maintainer, my bad,
> but since there's a debian/ subdirectory in the source tree, I thought
> this might interest you.

This is the right place to discuss all heartbeat development
related issues.

> The latest apache2.2-common update in Debian lenny (2.2.9-5) breaks the
> hearbeat ocf resource agent heuristics that determine what user to run
> it as and where to put the pid file. The apache2.conf now sports
>
> PidFile ${APACHE_PID_FILE}
> User ${APACHE_RUN_USER}
> Group ${APACHE_RUN_GROUP}
>
> instead of the actual place and user/group ids, which are specified in
> /etc/apache2/envvars like so:
>
> export APACHE_RUN_USER=www-data
> export APACHE_RUN_GROUP=www-data
> export APACHE_PID_FILE=/var/run/apache2.pid
>
> Since the resource agent basically greps the apache configuration for
> these, it ends up using ${APACHE_FOO_BAR}, and since
> /etc/apache2/envvars is never read, leaves them empty - which makes the
> whole thing fail miserably.
>
> In principle, the fix for this is trivial - the resource agent just has
> to do something like
>
> if [ -e /etc/apache2/envvars ]; then
> . /etc/apache2/envvars
> fi

The fix is not that trivial: the apache would understand, but the
RA wouldn't, because it parses the apache configuration without
expanding variables.

> before the action starts - this is what /etc/init.d/apache2 does.
> However, I am unsure whether hardcoding it in this manner is the right
> way to go - it might be prudent to make it a runtime variable like
> OCF_RESKEY_configfile, only to be loaded if specified.
>
> What do you think?

Thanks for bringing this up.

I'm not sure if we should deal with this at all in heartbeat.
Trying to support all the new setups and distributions, it may
become a nightmare. For the maintenance too: dealing with the
apache configuration is already rather complex and I'm really
reluctant to make it more so. However, since apache now supports
variables in the config and that may become a norm in future,
perhaps we should support environment variables too. Sigh.

Another option may be to kindly ask the apache people to provide
some facility to query the server configuration.

In the meantime, just don't use environment variables in the
configuration.

Can you please file an enhancement bugzilla.

Cheers,

Dejan

> Regards,
>
> Florian Knauf
> _______________________________________________________
> Linux-HA-Dev: Linux-HA-Dev[at]lists.linux-ha.org
> http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev
> Home Page: http://linux-ha.org/
_______________________________________________________
Linux-HA-Dev: Linux-HA-Dev[at]lists.linux-ha.org
http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev
Home Page: http://linux-ha.org/

lmb at suse

Jul 20, 2008, 11:51 AM

Post #3 of 7 (520 views)
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Re: Apache resource agent broken in Debian lenny [In reply to]

On 2008-07-20T17:30:20, Dejan Muhamedagic <dejanmm[at]fastmail.fm> wrote:

> I'm not sure if we should deal with this at all in heartbeat.
> Trying to support all the new setups and distributions, it may
> become a nightmare. For the maintenance too: dealing with the
> apache configuration is already rather complex and I'm really
> reluctant to make it more so. However, since apache now supports
> variables in the config and that may become a norm in future,
> perhaps we should support environment variables too. Sigh.

The first step is to allow a manual setting of everything which is
normally retrieved from auto-detection; validate-all could at least be
able to identify if some variable isn't in the right format (ie,
auto-detection failed), and then flag a request to specify it.

If people then use ocf-tester before adding something to their
configuration, they'll find out quickly ;-)

> Another option may be to kindly ask the apache people to provide
> some facility to query the server configuration.

Yes, that I guess would be good too. It's not our job to parse arbitrary
configuration files which happen to be in such inconvenient formats -
they really should switch to XML. *ducks & runs* ;-)

Regards,
Lars

--
Teamlead Kernel, SuSE Labs, Research and Development
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG N�rnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde

_______________________________________________________
Linux-HA-Dev: Linux-HA-Dev[at]lists.linux-ha.org
http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev
Home Page: http://linux-ha.org/

f.knauf at mmkf

Jul 20, 2008, 12:40 PM

Post #4 of 7 (523 views)
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Re: Apache resource agent broken in Debian lenny [In reply to]

Hi,

>> In principle, the fix for this is trivial - the resource agent just has
>> to do something like
>>
>> if [ -e /etc/apache2/envvars ]; then
>> . /etc/apache2/envvars
>> fi
>
> The fix is not that trivial: the apache would understand, but the
> RA wouldn't, because it parses the apache configuration without
> expanding variables.

Well, it worked for me. I can see how it could cause problems with
variable expansion, though - it's really something of a dirty hack this way.

> I'm not sure if we should deal with this at all in heartbeat.
> Trying to support all the new setups and distributions, it may
> become a nightmare.

True, that can be quite problematic. The initng project had major
problems with precisely that - it was messy, let me tell you.

Mind you, with the plethora of services that someone might want to
cluster, I expect admins usually wind up writing their own agents for
most of them, anyway. Excepting the most basic ones (like, say, drbd),
it might not be feasible to provide anything beyond "This worked for
someone, maybe you can tweak it to your needs," anyway. In the context
of debian packages, this might mean declaring everything in
/usr/lib/ocf/resource.d/heartbeat a configuration file, so that future
updates don't overwrite any custom changes that might have been applied.

However...

> For the maintenance too: dealing with the
> apache configuration is already rather complex and I'm really
> reluctant to make it more so. However, since apache now supports
> variables in the config and that may become a norm in future,
> perhaps we should support environment variables too. Sigh.
>
> Another option may be to kindly ask the apache people to provide
> some facility to query the server configuration.

>From what I can see, the apache RA basically replicates functionality
that's already part of apache2ctl - which is supposed to be used to
start, stop and control apache, anyway. Apache2ctl evaluates the envvars
file if it finds it, and uses appropriate default values or shell
overrides if it doesn't. I think this and all related problems would
vanish if the resource agent used it instead of calling the apache
binary directly, and it would make the whole thing a _lot_ simpler.

> Can you please file an enhancement bugzilla.

I will, but I'd like to run some tests with apache2ctl first to make
sure I'm correct about the above paragraph. If I find the time, I may
write a proof-of-concept RA, although I probably won't be able to test
that before next weekend - I'll have to remember how I built that
virtual testing cluster last time. :D

In other words, I'll get it into bugzilla as soon as I'm sure what I
write is correct.

Regards,

Florian Knauf

_______________________________________________________
Linux-HA-Dev: Linux-HA-Dev[at]lists.linux-ha.org
http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev
Home Page: http://linux-ha.org/

lmb at suse

Jul 20, 2008, 1:17 PM

Post #5 of 7 (519 views)
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Re: Apache resource agent broken in Debian lenny [In reply to]

On 2008-07-20T21:40:12, Florian Knauf <f.knauf[at]mmkf.de> wrote:

> From what I can see, the apache RA basically replicates functionality
> that's already part of apache2ctl - which is supposed to be used to
> start, stop and control apache, anyway. Apache2ctl evaluates the envvars
> file if it finds it, and uses appropriate default values or shell
> overrides if it doesn't. I think this and all related problems would
> vanish if the resource agent used it instead of calling the apache
> binary directly, and it would make the whole thing a _lot_ simpler.

Oh, I totally approve!

Be our hero, submit a patch ;-) If we meet, pizza is on me!

Regards,
Lars

--
Teamlead Kernel, SuSE Labs, Research and Development
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG N�rnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde

_______________________________________________________
Linux-HA-Dev: Linux-HA-Dev[at]lists.linux-ha.org
http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev
Home Page: http://linux-ha.org/

f.knauf at mmkf

Jul 21, 2008, 4:33 PM

Post #6 of 7 (499 views)
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Re: Apache resource agent broken in Debian lenny [In reply to]

Lars Marowsky-Bree schrieb:

> Oh, I totally approve!
>
> Be our hero, submit a patch ;-) If we meet, pizza is on me!

Well, alright. Who can say no to pizza? :-D

I attached a pre-alpha, untested,
do-not-use-in-production-unless-you-are-a-complete-lunatic version of
what I have in mind. I hacked it together just now in a very short time,
after a stressful day involving a failing mail relay and a very
bureaucratic telephone company, but it should give you a rough idea of
where I'm going with this, and whether you like the general approach.

Scroll past the metadata (which I blatantly copied from the old script)
to get to the action. The idea pretty much is to set some environment
variables and outsource all the real work to apache2ctl, then deal with
its results.

Also, I have one question - the current apache RA has a status command,
which apparently checks whether the process in the pid file is running.
I couldn't find this at http://www.linux-ha.org/OCFResourceAgent , and
it does seem to serve pretty much the same ends as monitor, so I clipped
it for now. Is this a horrible idea because the status command is
absolutely essential for the script to function, or am I within my
rights there?

Regards,

Florian Knauf

Attachments:

apache (3.32 KB)

f.knauf at mmkf

Jul 22, 2008, 3:54 PM

Post #7 of 7 (486 views)
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Re: Apache resource agent broken in Debian lenny (Heads up) [In reply to]

Hi,

Dejan Muhamedagic schrieb:

> Can you please file an enhancement bugzilla.

It is done:

http://developerbugs.linux-foundation.org/show_bug.cgi?id=1943

Regards,

Florian Knauf
_______________________________________________________
Linux-HA-Dev: Linux-HA-Dev[at]lists.linux-ha.org
http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev
Home Page: http://linux-ha.org/

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