Gluster users - Oct 2016 - rot-13 Translator query

On 10/15/2016 08:22 PM, Ankireddypalle Reddy wrote:
>
> Hi,
>
>       I am trying to follow the below document for developing a 
> translator.
>
>
https://github.com/gluster/glusterfs/blob/master/doc/developer-guide/translator-development.md
>
>       I?ve created a replica volume and modified the vol file to 
> include rot-13 translator. Below is the snippet from vol file.
>
> volume myvol-posix
>
>     type storage/posix
>
>     option volume-id b492191e-77a5-4fc3-9394-49218e36dae2
>
>     option directory /brick1/repli
>
> end-volume
>
> volume *myvol-rot13*
>
>     type encryption/rot-13
>
>     subvolumes *myvol-posix*
>
> end-volume
>
> volume myvol-trash
>
>     type features/trash
>
>     option trash-internal-op off
>
>     option brick-path /brick1/repli
>
>     option trash-dir .trashcan
>
>     subvolumes *myvol-rot13*
>
> end-volume
>
> ?
>
> The writes are getting intercepted by the translator and the file is 
> getting encrypted. But the reads don?t seem to be getting intercepted 
> by the translator.  I tried setting break point in the posix_readv 
> function and attach the brick daemons to gdb. But posix_readv does not 
> seem to be getting called on the brick daemon and the read completes 
> on the application side.
>
> Can someone please explain how the reads are getting serviced here 
> without hitting the posix layer.
>
It could be due to client side caching. I usually disable all 
performance xlators (write-behind, read-head, io-cache, stat-prefetch, 
quick-read, open-behind) when I want to remove caching effects while 
debugging. drop-caches also helps.

HTH,
Ravi
> Thanks and Regards,
>
> Ram
>
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The encryption xlator is the last one before posix and it's here that the
data is getting encrypted.  When the data is read back the encrypted data is
returned. Decryption is supposed to happen in read callback which does not seem
to be happening. The fact that encrypted data is getting returned indicates that
data in turn is getting returned from the posix/underlying fs layer.  Is it
possible that data be returned by reading from the underlying fs by any
translator other than posix.

Thanks and Regards,
Ram
From: Ravishankar N [mailto:ravishankar at redhat.com]
Sent: Sunday, October 16, 2016 12:19 AM
To: Ankireddypalle Reddy; gluster-users at gluster.org
Subject: Re: [Gluster-users] rot-13 Translator query

On 10/15/2016 08:22 PM, Ankireddypalle Reddy wrote:
Hi,
      I am trying to follow the below document for developing a translator.
     
https://github.com/gluster/glusterfs/blob/master/doc/developer-guide/translator-development.md

      I've created a replica volume and modified the vol file to include
rot-13 translator. Below is the snippet from vol file.

volume myvol-posix
    type storage/posix
    option volume-id b492191e-77a5-4fc3-9394-49218e36dae2
    option directory /brick1/repli
end-volume

volume myvol-rot13
    type encryption/rot-13
    subvolumes myvol-posix
end-volume

volume myvol-trash
    type features/trash
    option trash-internal-op off
    option brick-path /brick1/repli
    option trash-dir .trashcan
    subvolumes myvol-rot13
end-volume
...

The writes are getting intercepted by the translator and the file is getting
encrypted. But the reads don't seem to be getting intercepted by the
translator.  I tried setting break point in the posix_readv function and attach
the brick daemons to gdb. But posix_readv does not seem to be getting called on
the brick daemon and the read completes on the application side.

Can someone please explain how the reads are getting serviced here without
hitting the posix layer.
It could be due to client side caching. I usually disable all performance
xlators (write-behind, read-head, io-cache, stat-prefetch, quick-read,
open-behind) when I want to remove caching effects while debugging. drop-caches
also helps.

HTH,
Ravi



Thanks and Regards,
Ram
***************************Legal Disclaimer***************************
"This communication may contain confidential and privileged material for
the
sole use of the intended recipient. Any unauthorized review, use or distribution
by others is strictly prohibited. If you have received the message by mistake,
please advise the sender by reply email and delete the message. Thank you."
**********************************************************************



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***************************Legal Disclaimer***************************
"This communication may contain confidential and privileged material for
the
sole use of the intended recipient. Any unauthorized review, use or distribution
by others is strictly prohibited. If you have received the message by mistake,
please advise the sender by reply email and delete the message. Thank you."
**********************************************************************
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