[mapserver-users] mapcache in a cluster

[thomas bonfort]

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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