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

[Niels de Vos]

On Thu, Jan 05, 2017 at 11:26:19PM -0500, Vijay Bellur wrote:
> On Thu, Jan 5, 2017 at 8:40 AM, Niels de Vos <ndevos at redhat.com> wrote:
> 
> > 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?
> >
> >
> Sounds good to me. What are the additional improvements that you envision
> for 3?

I dont remember anymore and will look into this further next week.

Niels
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