[Gluster-users] GlusterFS and Kafka

[Vijay Bellur]

On Mon, May 22, 2017 at 11:49 AM, Joe Julian <joe at julianfamily.org> wrote:

> This may be asking too much, but can you explain why or how it's even
> possible to bypass the cache like this, Vijay?
>

This is a good question and the answers to that is something I should have
elaborated a bit more in my previous response. As far as the why is
concerned, gluster's client stack is configured by default to provide
reasonable performance and not  be very strongly consistent for
applications that need the most accurate metadata for their functioning.
Turning off the performance translators provide more stronger consistency
and we have seen applications that rely on a high degree of consistency
work better with that configuration. It is with this backdrop I suggested
performance translators be turned off from the client stack for Kafka.

On how it is possible, the translator model of gluster helps us to enable
or disable optional functionality from the stack. There is no single
configuration that can accommodate workloads with varying profiles and
having a modular architecture is a plus for gluster - the storage stack can
be tuned to suit varying application profiles. We are exploring the
possibility of providing custom profiles (collections of options) for
popular applications to make it easier for all of us. Note that disabling
performance translators in gluster is similar to turning off caching with
the NFS client. In parallel we are also looking to alter the behavior of
performance translators to provide as much consistency as possible by
default.

Thanks,
Vijay

>
>
> On May 22, 2017 7:41:40 AM PDT, Vijay Bellur <vbellur at redhat.com> wrote:
>>
>> Looks like a problem with caching. Can you please try by disabling all
>> performance translators? The following configuration commands would disable
>> performance translators in the gluster client stack:
>>
>> gluster volume set <volname> performance.quick-read off
>> gluster volume set <volname> performance.io-cache off
>> gluster volume set <volname> performance.write-behind off
>> gluster volume set <volname> performance.stat-prefetch off
>> gluster volume set <volname> performance.read-ahead off
>> gluster volume set <volname> performance.readdir-ahead off
>> gluster volume set <volname> performance.open-behind off
>> gluster volume set <volname> performance.client-io-threads off
>>
>> Thanks,
>> Vijay
>>
>>
>>
>> On Mon, May 22, 2017 at 9:46 AM, Christopher Schmidt <fakod666 at gmail.com>
>> wrote:
>>
>>> Hi all,
>>>
>>> has anyone ever successfully deployed a Kafka (Cluster) on GlusterFS
>>> volumes?
>>>
>>> I my case it's a Kafka Kubernetes-StatefulSet and a Heketi GlusterFS.
>>> Needless to say that I am getting a lot of filesystem related exceptions
>>> like this one:
>>>
>>> Failed to read `log header` from file channel
>>> `sun.nio.ch.FileChannelImpl at 67afa54a`. Expected to read 12 bytes, but
>>> reached end of file after reading 0 bytes. Started read from position
>>> 123065680.
>>>
>>> I limited the amount of exceptions with the log.flush.interval.messages=1
>>> option, but not all...
>>>
>>> best Christopher
>>>
>>>
>>> _______________________________________________
>>> Gluster-users mailing list
>>> Gluster-users at gluster.org
>>> http://lists.gluster.org/mailman/listinfo/gluster-users
>>>
>>
>>
> --
> Sent from my Android device with K-9 Mail. Please excuse my brevity.
>
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