[mapserver-users] mapcache in a cluster

[Travis Kirstine]

It appears the issue was hardware related, everything seems to be
working now with nfs

Thanks for your help



On 21 November 2011 11:12, Stephen Woodbridge <woodbri at swoodbridge.com> wrote:
> Travis,
>
> In the past I have used NFS in a custer and in general the performance was
> very bad when compared to SMB. Now this was a few years ago, ie: not using
> mapcache, but my experience was that we ran into a few issues with NFS:
>
> 1. NFS CPU overhead was significantly more
> 2. connection recovery was poor if a server was pulled from the cluster and
> added back again (ie: recovery after an error condition)
> 3. the protocol seems to have a lot more over head
>
> -Steve W
>
> On 11/21/2011 9:39 AM, thomas bonfort wrote:
>>
>> 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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>>>>> mapserver-users at lists.osgeo.org
>>>>> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>>>>>
>>>>
>>>
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