[Linux-cluster] Deadlock when using clvmd + OpenAIS + Corosync
Christine Caulfield
ccaulfie at redhat.com
Mon Jan 25 10:32:05 UTC 2010
On 23/01/10 17:35, Evan Broder wrote:
> On Fri, Jan 22, 2010 at 6:41 AM, Christine Caulfield
> <ccaulfie at redhat.com> wrote:
>> On 21/01/10 15:17, Evan Broder wrote:
>>>
>>> On Wed, Jan 13, 2010 at 4:59 AM, Christine Caulfield
>>> <ccaulfie at redhat.com> wrote:
>>>>
>>>> On 12/01/10 16:21, Evan Broder wrote:
>>>>>
>>>>> On Tue, Jan 12, 2010 at 3:54 AM, Christine Caulfield
>>>>> <ccaulfie at redhat.com> wrote:
>>>>>>
>>>>>> On 11/01/10 09:38, Christine Caulfield wrote:
>>>>>>>
>>>>>>> On 11/01/10 09:32, Evan Broder wrote:
>>>>>>>>
>>>>>>>> On Mon, Jan 11, 2010 at 4:03 AM, Christine Caulfield
>>>>>>>> <ccaulfie at redhat.com> wrote:
>>>>>>>>>
>>>>>>>>> On 08/01/10 22:58, Evan Broder wrote:
>>>>>>>>>>
>>>>>>>>>> [please preserve the CC when replying, thanks]
>>>>>>>>>>
>>>>>>>>>> Hi -
>>>>>>>>>> We're attempting to setup a clvm (2.02.56) cluster using OpenAIS
>>>>>>>>>> (1.1.1) and Corosync (1.1.2). We've gotten bitten hard in the past
>>>>>>>>>> by
>>>>>>>>>> crashes leaving DLM state around and forcing us to reboot our
>>>>>>>>>> nodes,
>>>>>>>>>> so we're specifically looking for a solution that doesn't involve
>>>>>>>>>> in-kernel locking.
>>>>>>>>>>
>>>>>>>>>> We're also running the Pacemaker OpenAIS service, as we're hoping
>>>>>>>>>> to
>>>>>>>>>> use it for management of some other resources going forward.
>>>>>>>>>>
>>>>>>>>>> We've managed to form the OpenAIS cluster, and get clvmd running on
>>>>>>>>>> both of our nodes. Operations using LVM succeed, so long as only
>>>>>>>>>> one
>>>>>>>>>> operation runs at a time. However, if we attempt to run two
>>>>>>>>>> operations
>>>>>>>>>> (say, one lvcreate on each host) at a time, they both hang, and
>>>>>>>>>> both
>>>>>>>>>> clvmd processes appear to deadlock.
>>>>>>>>>>
>>>>>>>>>> When they deadlock, it doesn't appear to affect the other
>>>>>>>>>> clustering
>>>>>>>>>> processes - both corosync and pacemaker still report a fully formed
>>>>>>>>>> cluster, so it seems the issue is localized to clvmd.
>>>>>>>>>>
>>>>>>>>>> I've looked at logs from corosync and pacemaker, and I've straced
>>>>>>>>>> various processes, but I don't want to blast a bunch of useless
>>>>>>>>>> information at the list. What information can I provide to make it
>>>>>>>>>> easier to debug and fix this deadlock?
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> To start with, the best logging to produce is the clvmd logs which
>>>>>>>>> can be
>>>>>>>>> got with clvmd -d (see the man page for details). Ideally these
>>>>>>>>> should be
>>>>>>>>> from all nodes in the cluster so they can be correlated. If you're
>>>>>>>>> still
>>>>>>>>> using DLM then a dlm lock dump from all nodes is often helpful in
>>>>>>>>> conjunction with the clvmd logs.
>>>>>>>>
>>>>>>>> Sure, no problem. I've posted the logs from clvmd on both processes
>>>>>>>> in
>>>>>>>> <http://web.mit.edu/broder/Public/clvmd/>. I've annotated them at a
>>>>>>>> few points with what I was doing - the annotations all start with "
>>>>>>>>>>
>>>>>>>>>> ", so they should be easy to spot.
>>>>>>
>>>>>>
>>>>>> Ironically it looks like a bug in the clvmd-openais code. I can
>>>>>> reproduce
>>>>>> it
>>>>>> on my systems here. I don't see the problem when using the dlm!
>>>>>>
>>>>>> Can you try -Icorosync and see if that helps? In the meantime I'll have
>>>>>> a
>>>>>> look at the openais bits to try and find out what is wrong.
>>>>>>
>>>>>> Chrissie
>>>>>>
>>>>>
>>>>> I'll see what we can pull together, but the nodes running the clvm
>>>>> cluster are also Xen dom0's. They're currently running on (Ubuntu
>>>>> Hardy's) 2.6.24, so upgrading them to something new enough to support
>>>>> DLM 3 would be...challenging.
>>>>>
>>>>> It would be much, much better for us if we could get clvmd-openais
>>>>> working.
>>>>>
>>>>> Is there any chance this would work better if we dropped back to
>>>>> openais whitetank instead of corosync + openais wilson?
>>>>>
>>>>
>>>>
>>>> OK, I've found the bug and it IS in openais. The attached patch will fix
>>>> it.
>>>>
>>>> Chrissie
>>>>
>>>
>>> Awesome. That patch fixed our problem.
>>>
>>> We are running into one other problem - performing LVM operations on
>>> one node is substantially slower than performing them on the other
>>> node:
>>>
>>> root at black-mesa:~# time lvcreate -n test -L 1G xenvg
>>> Logical volume "test" created
>>>
>>> real 0m0.309s
>>> user 0m0.000s
>>> sys 0m0.008s
>>> root at black-mesa:~# time lvremove -f /dev/xenvg/test
>>> Logical volume "test" successfully removed
>>>
>>> real 0m0.254s
>>> user 0m0.004s
>>> sys 0m0.008s
>>>
>>>
>>> root at torchwood-institute:~# time lvcreate -n test -L 1G xenvg
>>> Logical volume "test" created
>>>
>>> real 0m7.282s
>>> user 0m6.396s
>>> sys 0m0.312s
>>> root at torchwood-institute:~# time lvremove -f /dev/xenvg/test
>>> Logical volume "test" successfully removed
>>>
>>> real 0m7.277s
>>> user 0m6.420s
>>> sys 0m0.292s
>>>
>>> Any idea why this is happening and if there's anything we can do about it?
>>>
>>
>>
>> I'm not at all sure why that should be happening. I suppose the best thing
>> to do would be to enable clvmd logging (clvmd -d) and see what is taking the
>> time.
>>
>> Chrissie
>>
>
> No problem. I've collected another set of logs - they're in
> <http://web.mit.edu/broder/Public/clvmd-slow/>.
>
> After spinning up corosync and clvmd, the commands I ran were, in order:
>
> root at black-mesa:~# vgchange -a y xenvg
> 0 logical volume(s) in volume group "xenvg" now active
> root at black-mesa:~# time lvcreate -n test1 -L 1G xenvg
> Logical volume "test1" created
>
> real 0m0.685s
> user 0m0.004s
> sys 0m0.000s
> root at black-mesa:~# time lvremove -f /dev/xenvg/test1
> Logical volume "test1" successfully removed
>
> real 0m0.235s
> user 0m0.004s
> sys 0m0.004s
> root at torchwood-institute:~# time lvcreate -n test2 -L 1G xenvg
> Logical volume "test2" created
>
> real 0m8.007s
> user 0m6.396s
> sys 0m0.312s
> root at torchwood-institute:~# time lvremove -f /dev/xenvg/test2
> Logical volume "test2" successfully removed
>
> real 0m7.364s
> user 0m6.436s
> sys 0m0.300s
> root at black-mesa:~# vgchange -a n xenvg
> 0 logical volume(s) in volume group "xenvg" now active
>
> (black-mesa is node 1, and torchwood-institute is node 2)
>
> Thanks again for your help,
>
Hiya,
Oddly I can't find any delays in the clvmd logs at all. There are some
7-second gaps in the log files but those are between commands coming
from the lvm command-line and not internal to clvmd itself.
What sort of storage are you using for these LVs? The only thing I can
think of now is that there is some sort of delay in lvm opening the
device for writing as it updates the metadata. An LVM debug log might be
helpful here, though I'm not sure, off-hand, how to put time-stamps on
that - I'm not really an LVM developer any more.
Chrissie
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