[Gluster-Maintainers] [Gluster-devel] RFC: Gluster.Next: Where and how DHT2 work/code would be hosted

Mon Oct 12 14:06:44 UTC 2015

On 10/11/2015 06:09 PM, Niels de Vos wrote:
> On Fri, Oct 09, 2015 at 10:40:15AM -0400, Shyam wrote:
>> On 10/09/2015 12:07 AM, Atin Mukherjee wrote:
>>> First of all my apologies for not going through the meeting blog before
>>> sending my thoughts on how we plan to maintain GlusterD 2.0 [1].
>>>
>>> This approach seems fine to me as long as we don't touch any existing
>>> xlators. How do we handle cases where other xlators get impacted by
>>> certain changes. Are we going to copy the whole translator in
>>> xlators/experimental and start working on it?
>>
>> Nope, we should send a change request for that xlator as a separate commit
>> when possible.
>>
>> The counter example to this is, point (4) below (where DHT2 needs a bit of
>> change in glusterd, but ...).
>>
>> I suggest such changes be maintained as .patch files inside the xlator, till
>> a point when this can be merged is decided.
>
> No, please not, this makes it practically impossible to track the
> history of the changes. See this other email that suggests using
> different functions based on a #define:
>
>    http://www.gluster.org/pipermail/gluster-devel/2015-October/046889.html
>
> This is clean, does not need nasty hacks in the build system and keeps
> the history. Also, when someone changes one variation of the function,
> the other variation would get corrected at the same time (or the
> reviewers point that missing bit out).

The #if/else approach works for me, the only problem is that we should 
not pollute the supported code too much, that it becomes difficult to 
maintain, or newer functionality causes unstable behaviour.

>
>>> Instead of all this wouldn't it be simpler to have development under a
>>> separate branch say "4.0-unstable" and we could disable CI on this
>>> branch till it becomes stable? Are we worried about pulling in the
>>> changes from this to master once the branch becomes stable?
>>
>> I guess the worry is *bulk* changes appearing in master (as per meeting
>> minutes). I share the same concern as well (on bulk changes), but I am
>> unsure of review stringency on experimental, as things will evolve here,
>> than each commit be ready for a clean review from day 1. So, this is an open
>> confusion in my head as well, as when we want to move an xlator from
>> experimental to suported, what would be the criteria? Would we not be doing
>> bulk reviews then as well?
>
> Changes for a new feature should also be done in steps that can
> reasonably be reviewed, so, smaller patches addressing a particular
> functionality. Developers that are interested in the feature, should
> have a good review process. The standards that we apply for
> non-experimental changes are strict, but is there really a good reason
> to not apply those guidelines for patches to expiremental xlators too?

There are 2 sub-problems here, and I think I answered on of them in 
another mail, which is *bulk* changes. The short of it being, yes there 
would be incremental changes to the experimental code base, but *when* 
it has to move out of experimental, that move may need a bulk review, we 
cannot get away from this in any scheme, and with code in master, there 
is a good chance that, as the xlator matures more eyes are called in to 
review the changes, so the bulk point is rather not as bulky and should 
become moot. IOW, *bulk* is no longer a concern (at least for me with 
the master branch+experimental approach).

The second issue I see here is the quality of each submission and the 
review process around it etc. I would answer it this way, code that 
compiles may not work or could have issues during integration, or things 
under experimental would change course during its lifetime. As a result, 
some experimental changes would be allowed, and hence move forward the 
development or thought process, to a point where we are in functioning 
order at some time. Having a very stringent review and working order 
code in experimental, could hamper development pace.

>
> I guess each experimental xlator should have a TODO list in its sources.
> If a reviewer notices some issue, it may be acceptible to add the
> problem to the TODO list (with a pointer to the review URL where it was
> spotted). This allows fast progress, and we have some criteria that gets
> collected with which we can decide if the xlator may move out of
> experimental. It also makes it possible for others to update the TODO
> list when reviews of the already merged code is done.

This is better, I was using TODO in code for the same, a list of issues 
is better to track, close, check etc.

I will add this to the criteria in the commit for the same.

>
> Niels
>
>>
>> What do others think?
>>
>>>
>>> This is just my thought and I would like to get a clarity on this.
>>>
>>> Thanks,
>>> Atin
>>>
>>> [1] http://www.gluster.org/pipermail/gluster-devel/2015-October/046872.html
>>>
>>> On 10/08/2015 11:35 PM, Shyam wrote:
>>>> Hi,
>>>>
>>>> On checking yesterday's gluster meeting AIs and (later) reading the
>>>> minutes, for DHT2 here is what I gather and propose to do for $SUBJECT.
>>>> Feel free to add/negate any plans.
>>>>
>>>> (This can also be discussed at [2])
>>>>
>>>> -------------------------------------------------------------------
>>>> 1) Create a directory under the glusterfs master branch as follows,
>>>> ./xlators/*experimental*/dht2
>>>> ./xlators/*experimental*/posix2
>>>>
>>>> See patch request at [2]
>>>>
>>>> All code, design documents (work products in general) would go into this
>>>> directory.
>>>>
>>>> 2) Code that compiles and does not cause CI failures could *potentially*
>>>> be merged with very few DHT2 dev folks assent.
>>>>
>>>> There would possibly be no CI integration till we get something working,
>>>> so merges would be based on compile passing initially. Soon there would
>>>> be an attempt at getting unit testing integrated, so that code being
>>>> submitted is not abysmally horrendous
>>>>
>>>> 3) Common framework code changes (if any) would be presented as a
>>>> separate commit request
>>>>
>>>> 4) (Big problem) DHT2 requires glusterd changes to create a volume as
>>>> DHT2 and not DHT, this would be maintained as a .patch in the dht2
>>>> directory as above. This is so that people can play with DHT2 volumes if
>>>> interested. Integration of this piece either comes with glusterd 2.0 or
>>>> based on time lines of other events, in the current version of glusterd.
>>>> (if you are interested in seeing the current version of this patch, go
>>>> here [1])
>>>> -------------------------------------------------------------------
>>>>
>>>> If there is some key disagreement on certain points like (2) above, then
>>>> we would need to bring in DHT2 code in parts so that it makes sense.
>>>> This is fine too, just that we would have 2 repos till we reach a point
>>>> of maturity in development.
>>>>
>>>> -------------------------------------------------------------------
>>>> *Some issues with the approach:*
>>>> A) We need to ensure we do not ship xlators compiled from the
>>>> experimental directory
>>>>
>>>> B) We need to possibly add a buddy maintainer for experimental
>>>> translator owners, who can help with the process of merging their changes.
>>>>
>>>> C) I am not sure how this helps the review process, as initially xlator
>>>> development can be iffy and so we do not expect reviews to be stringent.
>>>> Later when we want to move this out of the experimental category, how do
>>>> we review the same now, and what actions do we take to ensure quality?
>>>> Won't we have the same bulk code review issue?
>>>> -------------------------------------------------------------------
>>>>
>>>> Shameless plug: For quality and if an xlator plays well with other parts
>>>> of gluster the distaf framework of testing against possible graphs and
>>>> access protocols can be of immense help.
>>>>
>>>> Shyam
>>>>
>>>> [1]
>>>> https://github.com/ShyamsundarR/glusterfs/commit/663eeb98f6a51384c8745b8882e7c6c4f7b58a7c
>>>>
>>>> [2] http://review.gluster.org/#/c/12321/1
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