[Gluster-devel] Release 3.10 feature proposal:: Statedump for libgfapi

[Niels de Vos]

On Wed, Dec 14, 2016 at 11:28:43AM +0530, Rajesh Joseph wrote:
> On Mon, Dec 12, 2016 at 11:34 PM, Shyam <srangana at redhat.com> wrote:
> > On 12/12/2016 12:26 AM, Niels de Vos wrote:
> >>
> >> On Fri, Dec 09, 2016 at 06:20:22PM +0530, Rajesh Joseph wrote:
> >>>
> >>> Gluster should have some provision to take statedump of gfapi
> >>> applications.
> >>>
> >>> https://bugzilla.redhat.com/show_bug.cgi?id=1169302
> >>
> >>
> >> A part of this feature should be to find out how applications that use
> >> libgfapi expect to trigger debugging like this. Doing a statedump from
> >> the gluster-cli should not be the main/only option. I agree that it
> >> helps developers that work on Gluster, but we can not expect users to
> >> trigger statedumps like that.
> >>
> >> I think there would be a huge benefit in having an option to communicate
> >> with libgfapi through some minimal form of local IPC. It will allow
> >> doing statedumps, and maybe even set/get configuration options for
> >> applications that do not offer these in their usage (yet).
> >>
> >> The communication should be as simple and stable as possible. This could
> >> be the only working interface towards getting something done inside
> >> gfapi (worst case scenario). There is no need to have this a full
> >> featured interface, possibly a named pipe (fifo) where libgfapi is the
> >> reader is sufficient. A simple (text) command written to it can create
> >> statedumps and eventually other files on request.
> >>
> >> Enabling/disabling or even selecting the possibilities for debugging
> >> could be confiured through new functions in libgfapi, and even
> >> environment variables.
> >>
> >> What do others think? Would this be useful?
> >
> >
> > Would this be useful, yes.
> >
> > Would this work in cases like a container deployment, where such debugging
> > maybe sought at scale, maybe not. I prefer options here, and also the
> > ability to drive this from the storage admin perspective, i.e the
> > server/brick end of things, identifying the client/connection against which
> > we need the statedump and get that information over.
> >
> 
> We were thinking something on the same line. Where statedumps can be
> initiated by
> glusterd by an admin. The option mentioned by Niels is also helpful
> but that means
> we should either provide some tool or the application has to do some
> amount of changes
> to make use of this feature.
> 
> > I guess the answer here is, this should not be the only option, but we
> > can/should have other options as you describe above.

I have not found a feature page for this, is there one?

Because we would really like this in 3.10 to allow applications to
integrate better with Gluster, I propose to split the functionality over
several changes:

1. ground work and API exposed for applications (and testing)
2. enablement through a simple interface, similar to /proc/sysrq-trigger
3. enablement through gluster-cli command

These options should be explained in the feature page, with the plan to
provide the three options for 3.10. I'm happy to massage the patch from
Poornima [0] and split it in 1 and 3. Additional improvements for 3
might be needed, and we'll have to see who does that work. Point 2 is
something I'll take on as well.

What do others think about this?

Thanks,
Niels

[0] http://review.gluster.org/9228
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