[Gluster-devel] [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?
Pranith Kumar Karampuri
pkarampu at redhat.com
Fri Jul 18 14:03:43 UTC 2014
On 07/18/2014 05:43 PM, Andrew Lau wrote:
>
> On Fri, Jul 18, 2014 at 10:06 PM, Vijay Bellur <vbellur at redhat.com
> <mailto:vbellur at redhat.com>> wrote:
>
> [Adding gluster-devel]
>
>
> On 07/18/2014 05:20 PM, Andrew Lau wrote:
>
> Hi all,
>
> As most of you have got hints from previous messages, hosted
> engine
> won't work on gluster . A quote from BZ1097639
>
> "Using hosted engine with Gluster backed storage is currently
> something
> we really warn against.
>
>
> I think this bug should be closed or re-targeted at
> documentation, because there is nothing we can do here. Hosted
> engine assumes that all writes are atomic and (immediately)
> available for all hosts in the cluster. Gluster violates those
> assumptions.
> "
>
> I tried going through BZ1097639 but could not find much detail
> with respect to gluster there.
>
> A few questions around the problem:
>
> 1. Can somebody please explain in detail the scenario that causes
> the problem?
>
> 2. Is hosted engine performing synchronous writes to ensure that
> writes are durable?
>
> Also, if there is any documentation that details the hosted engine
> architecture that would help in enhancing our understanding of its
> interactions with gluster.
>
>
>
>
> Now my question, does this theory prevent a scenario of perhaps
> something like a gluster replicated volume being mounted as a
> glusterfs
> filesystem and then re-exported as the native kernel NFS share
> for the
> hosted-engine to consume? It could then be possible to chuck
> ctdb in
> there to provide a last resort failover solution. I have tried
> myself
> and suggested it to two people who are running a similar
> setup. Now
> using the native kernel NFS server for hosted-engine and they
> haven't
> reported as many issues. Curious, could anyone validate my
> theory on this?
>
>
> If we obtain more details on the use case and obtain gluster logs
> from the failed scenarios, we should be able to understand the
> problem better. That could be the first step in validating your
> theory or evolving further recommendations :).
>
>
> I'm not sure how useful this is, but Jiri Moskovcak tracked this down
> in an off list message.
>
> Message Quote:
>
> ==
>
> We were able to track it down to this (thanks Andrew for providing the
> testing setup):
>
> -b686-4363-bb7e-dba99e5789b6/ha_agent service_type=hosted-engine'
> Traceback (most recent call last):
> File
> "/usr/lib/python2.6/site-packages/ovirt_hosted_engine_ha/broker/listener.py",
> line 165, in handle
> response = "success " + self._dispatch(data)
> File
> "/usr/lib/python2.6/site-packages/ovirt_hosted_engine_ha/broker/listener.py",
> line 261, in _dispatch
> .get_all_stats_for_service_type(**options)
> File
> "/usr/lib/python2.6/site-packages/ovirt_hosted_engine_ha/broker/storage_broker.py",
> line 41, in get_all_stats_for_service_type
> d = self.get_raw_stats_for_service_type(storage_dir, service_type)
> File
> "/usr/lib/python2.6/site-packages/ovirt_hosted_engine_ha/broker/storage_broker.py",
> line 74, in get_raw_stats_for_service_type
> f = os.open(path, direct_flag | os.O_RDONLY)
> OSError: [Errno 116] Stale file handle:
> '/rhev/data-center/mnt/localhost:_mnt_hosted-engine/c898fd2a-b686-4363-bb7e-dba99e5789b6/ha_agent/hosted-engine.metadata'
Andrew/Jiri,
Would it be possible to post gluster logs of both the mount and
bricks on the bz? I can take a look at it once. If I gather nothing then
probably I will ask for your help in re-creating the issue.
Pranith
>
> It's definitely connected to the storage which leads us to the
> gluster, I'm not very familiar with the gluster so I need to check
> this with our gluster gurus.
>
> ==
>
> Thanks,
> Vijay
>
>
>
>
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