[mapserver-users] mapcache in a cluster

[Travis Kirstine]

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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>