On 10/07/2016 12:10 PM, Sean McGinnis wrote:
On Fri, Oct 07, 2016 at 05:04:00PM +0200, [email protected] wrote:
Hi Erlon.
Thank you for the reply. I need to collect this information to generate sort of
overview of drivers used in given environment. Obviously, it potentially is a
multiple backed one. This information does not need to be pulled from the
cinder API - I can assume I work under root on host on which cinder service is
running.
Parsing of cinder.conf comes with usual problems related to trying to get
runtime information from config file. It is very prone to suddenly stop working
due to changes in OpenStack itself. We may also potentially run into a
situation in which config file has been modified, but Cinder has not been
restarted (or worse, file is currently being edited and we read garbage). Now,
if it comes to that I can live with those problems, but I was hoping a cleaner
solution exists (as mentioned earlier - volume_backend_name, defined in same
config, is very easy to retrieve).
Thanks again and best regards,
Lukasz
This type of information is not exposed via the API, since this is a
configuration detail that someone interacting with a cloud should not
have access to.
The format of cinder.conf does not change much, so grepping for the line
that starts with "volume_driver = " should be a very safe assumption to
make.
That does not address the case you mentioned of the cinder.conf possibly
being changed but the service not restarted yet. I think that's probably
a very low risk, but the only way I can think of to get around that is
to grep the current state out of the c-vol.log file. That would bring
with it many more risks though. There's not a standard location or even
name for that log file. And it's quite possible the volume drivers did
change, the service was restarted, but there's still a volume_driver
mentioned in the log that is not in fact used any more.
And it would also need to assume DEBUG level logging was enabled. So
really I think grep'ing cinder.conf is your best bet here.
Sean (smcginnis)
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As Sean states the cinder.conf file format has been stable for quite
some time. So, I don't think you need to worry about volume_driver
changing any time soon.
If you wanted an additional level of reassurance that you are getting
the right information you could check the number of c-vol processes
running on the system to ensure it matches the number of volume_driver
's specified in the config file. I think that it would be a rare case
where the user is swapping one backend for another. More likely to see
additive/subtractive changes. So, you could give yourself some
confidence by checking those numbers and comparing. Flagging when they
don't match.
Jay
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