[Linux-HA] OCF-RA and shell functions
mm at yuhu.biz
Wed Mar 17 04:35:08 MDT 2010
On Wednesday 17 March 2010 12:16:58 Andreas Mock wrote:
> Hi all,
> here some questions regarding programming ocf-ra:
> a) Am I right that programming a RA as portable shell script (no bashisms)
> is preferred? Or are other (scripting) languages also welcome?
I'm confident that no bashisms are allowed... this made me rewrite a lot of
things in the mysql RA. I don't think that other scripting languages are
allowed, but maybe Dejan can answer better here.
> b) I found RA scripts for daemons where the 'status' call checks for the
> existence of the daemon pid file and if that file is not there
> $OCF_NOT_RUNNING is returned. As all the cluster guys out there should be
> very pessimistic by default, I'm asking myself if this kind of check is
> really enough. On the one hand side much efford is taken to be REALLY sure
> that a ressource isn't alive anymore (fencing, STONITH) and on the other
> side the simple nonexistence of a file seems to be enough to assume (!)
> the relevant process isn't alive anymore.
> What are you thinking about that?
I don't really agree here. You are right that a missing pidfile is not enough.
However, it is required that a service is started with the RA for it. And it
is required that this RA or the Services handles the creation of the pidfile.
The idea is that you are depending on the same RA to check and verify if the
pidfile was created during the startup and this is way you depend on this pid
If you don't start your service from the RA then it is your problem and not
My point is that one should verify the pidfile after starting and do not mark
as started/running a service with a wrong or missing pidfile. This way we will
skip more useless checks.
> c) If you agree with me, that a explicit check for a running process would
> be more reliable, my next question is: Does anyone know how this can be
> done in a shell script in a portable and reliable manner? (e.g. ps ax with
> I found that 'ocf_pidfile_status' in .ocf-shellfuncs encapsulates a part of
> the required tests.
> Awaiting your comments and suggestions?
> Best regards
> Andreas Mock
> Linux-HA mailing list
> Linux-HA at lists.linux-ha.org
> See also: http://linux-ha.org/ReportingProblems
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