[Gluster-devel] xlator option setting in gfapi

Raghavendra Gowdappa rgowdapp at redhat.com
Mon May 9 06:47:25 UTC 2016



----- Original Message -----
> From: "Raghavendra Talur" <rtalur at redhat.com>
> To: "Raghavendra Gowdappa" <rgowdapp at redhat.com>
> Cc: "Poornima Gurusiddaiah" <pgurusid at redhat.com>, "Gluster Devel" <gluster-devel at gluster.org>, "Jeff Cody"
> <jcody at redhat.com>, "Rajesh Joseph" <rjoseph at redhat.com>
> Sent: Monday, May 9, 2016 11:57:44 AM
> Subject: Re: xlator option setting in gfapi
> 
> On Mon, May 9, 2016 at 8:45 AM, Raghavendra Gowdappa <rgowdapp at redhat.com>
> wrote:
> 
> > Hi Poornima/Raghavendra,
> >
> > This mail is an initiation of a thread to discuss how to make xlator
> > options setting in gfapi synchronous (so, that caller will know the result)
> > or providing a cbk to let the application know about the status.
> >
> > My very naive attempt of code-reading showed me that
> > pub_glfs_set_xlator_option just adds the option to cmd_args.xlator_options.
> > Can you please explain how/when these values are communicated to glusterd
> > to change volfile? From there we can carry forward the conversation.
> >
> >
> Raghavendra,
> 
> glfs_set_xlator_option is equivalent to --xlator-option of mount.glusterfs
> of FUSE. This feature is not intended to apply the setting to the volume
> permanently, rather it is specific to the mount and only valid for its
> lifetime.
> The current architecture of Gluster graph takes these options only in
> cmd_args and then these values are given preference over whatever comes in
> volfile from Glusterd. In essence, these settings can be used to override
> the volume settings for a particular mount.

For this use case, even a way to modify the options for a single mount is fine. But the problem is, how do I know whether the option I set has taken effect? Is checking return value of pug_glfs_set_xlator_option is sufficient (seems unlikely as I don't see any xlators being involved here)? Can you explain the mechanism involved here (as in how this option is propagated to relevant xlator - do we call reconfigure with new set of option dict etc)?

> 
> If the requirement is to set a volume wide option then glusterd or one of
> the REST interfaces for Glusterd should be used.
> 
> I will also reply to the other thread with possible methods on overcoming
> the problem with write-behind and qemu.
> 
> Thanks,
> Raghavendra Talur
> 
> 
> > regards,
> > Raghavendra
> >
> 


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