[mapserver-users] mapcache in a cluster

thomas bonfort thomas.bonfort at gmail.com
Mon Nov 21 09:39:44 EST 2011


What kind of performance issues? The current locking code only uses
the presence/absence of a file for it's locking functions, and does
not rely on flock/fcntl.

--
thomas

On Mon, Nov 21, 2011 at 15:16, Travis Kirstine <traviskirstine at gmail.com> wrote:
> Thomas,
>
> We have been running into some performance issues mapcache and nfs.
> We feel the issue may be related to how nfs locks files/directories
> compared to smb.  We are trying a few thing on our end (disable
> locking / nfs4 etc).  Do you have any ideas?
>
> Regards
>
> On 20 October 2011 12:19, thomas bonfort <thomas.bonfort at gmail.com> wrote:
>> So, this discussion inspired me to completely rework the locking
>> mechanism in mapcache, to stop relying on file locks which have their
>> quirks on network filesystems.
>> I have tried using multiple apache instances configured to used a
>> SMB-mounted lock directory and hammered both instances on unseeded
>> identical area to force locking, and ended up with absolutely no
>> duplicate wms requests or failed requests for the clients.
>> The code is committed in trunk. Thanks for bringing this up, this
>> allowed me to really simplify the locking code and remove a lot of
>> unneeded stuff :)
>>
>> --
>> thomas
>>
>> On Thu, Oct 20, 2011 at 17:08, Travis Kirstine <traviskirstine at gmail.com> wrote:
>>> Andreas and Thomas
>>>
>>> Thanks for you responses,  I have discussed this with some of our IT
>>> staff and they had similar solution as Andreas using gfs.  Their
>>> comments are below:
>>>
>>> "I suspect this scheme is not reliable over NFS. The problem is the
>>> directory updates are not synchronized across multiple nodes. I had a
>>> similar issue with the IMAP E-mail protocol. Our workaround currently
>>> is to force each user to leverage a single server.
>>>
>>> Ref:
>>> http://wiki.dovecot.org/NFS
>>>
>>> Seems like there's some tweaks to disable directory attribute caching
>>> but this can trigger slower performance.
>>> Only workaround is to use GFS which I found to have it's own issues. "
>>>
>>> Regards
>>>
>>>
>>>
>>> On 20 October 2011 05:32, Eichner, Andreas - SID-NLKM
>>> <Andreas.Eichner at sid.sachsen.de> wrote:
>>>>
>>>> We use TileCache.py on two servers with the cache on an OCFS2 on a
>>>> shared LUN in the SAN. No known issues with that for now. Note: Spurious
>>>> stale lock files occurred already on a single machine. There seemed to
>>>> be issues with lots of requests and a very slow upstream server. I used
>>>> a cron job to delete lock files older than 5 minutes or so.
>>>> As Thomas noted, if the lock files are created on a shared filesystem
>>>> and you make sure the filesystem you use is able to lock files properly
>>>> (read the docs carefully!) there's no reason why it should not work.
>>>>
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>>> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>>>
>>
>


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