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List:       cassandra-dev
Subject:    Re: Side Car New Repo vs not
From:       Sankalp Kohli <kohlisankalp () gmail ! com>
Date:       2018-08-28 4:10:37
Message-ID: 8B405305-9FE1-4E1C-A70C-CEB844FA1B29 () gmail ! com
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Thanks everyone for the feedback. Looks like we will go with separate repo as that is what majority of people prefer. 

Also note that we can always change this approach later as we build the side car. 

> On Aug 24, 2018, at 07:00, Eric Evans <john.eric.evans@gmail.com> wrote:
> 
>> On Thu, Aug 23, 2018 at 3:01 PM sankalp kohli <kohlisankalp@gmail.com> wrote:
>> 
>> Separate repo is in a majority so far. Please reply to this thread with
>> your responses.
> 
> I think it makes sense for the code, project, and workflows to be
> (de|loosely)-coupled, so the repo should be as well.
> 
> +1 for a separate repository
> 
>> On Tue, Aug 21, 2018 at 4:34 PM Rahul Singh <rahul.xavier.singh@gmail.com>
>> wrote:
>> 
>>> +1 for separate repo. Especially on git. Maybe make it a submodule.
>>> 
>>> Rahul
>>> On Aug 21, 2018, 3:33 PM -0500, Stefan Podkowinski <spod@apache.org>,
>>> wrote:
>>>> I'm also currently -1 on the in-tree option.
>>>> 
>>>> Additionally to what Aleksey mentioned, I also don't see how we could
>>>> make this work with the current build and release process. Our scripts
>>>> [0] for creating releases (tarballs and native packages), would need
>>>> significant work to add support for an independent side-car. Our ant
>>>> based build process is also not a great start for adding new tasks, let
>>>> alone integrating other tool chains for web components for a potential
>>> UI.
>>>> 
>>>> [0] https://git-wip-us.apache.org/repos/asf?p=cassandra-builds.git
>>>> 
>>>> 
>>>>> On 21.08.18 19:20, Aleksey Yeshchenko wrote:
>>>>> Sure, allow me to elaborate - at least a little bit. But before I do,
>>> just let me note that this wasn't a veto -1, just a shorthand for "I don't
>>> like this option".
>>>>> 
>>>>> It would be nice to have sidecar and C* version and release cycles
>>> fully decoupled. I know it *can* be done when in-tree, but the way we vote
>>> on releases with tags off current branches would have to change somehow.
>>> Probably painfully. It would be nice to be able to easily enforce freezes,
>>> like the upcoming one, on the whole C* repo, while allowing feature
>>> development on the sidecar. It would be nice to not have sidecar commits in
>>> emails from commits@ mailing list. It would be nice to not have C* CI
>>> trigger necessarily on sidecar commits. Groups of people working on the two
>>> repos will mostly be different too, so what's the point in sharing the repo?
>>>>> 
>>>>> Having an extra repo with its own set of branches is cheap and easy -
>>> we already do that with dtests. I like cleanly separated things when
>>> coupling is avoidable. As such I would prefer the sidecar to live in a
>>> separate new repo, while still being part of the C* project.
>>>>> 
>>>>> —
>>>>> AY
>>>>> 
>>>>> On 21 August 2018 at 17:06:39, sankalp kohli (kohlisankalp@gmail.com)
>>> wrote:
>>>>> 
>>>>> Hi Aleksey,
>>>>> Can you please elaborate on the reasons for your -1? This
>>>>> way we can make progress towards any one approach.
>>>>> Thanks,
>>>>> Sankalp
>>>>> 
>>>>> On Tue, Aug 21, 2018 at 8:39 AM Aleksey Yeshchenko <aleksey@apple.com>
>>>>> wrote:
>>>>> 
>>>>>> FWIW I'm strongly -1 on in-tree approach, and would much prefer a
>>> separate
>>>>>> repo, dtest-style.
>>>>>> 
>>>>>> —
>>>>>> AY
>>>>>> 
>>>>>> On 21 August 2018 at 16:36:02, Jeremiah D Jordan (
>>>>>> jeremiah.jordan@gmail.com) wrote:
>>>>>> 
>>>>>> I think the following is a very big plus of it being in tree:
>>>>>>>> * Faster iteration speed in general. For example when we need to
>>> add a
>>>>>>>> new
>>>>>>>> JMX endpoint that the sidecar needs, or change something from
>>> JMX to a
>>>>>>>> virtual table (e.g. for repair, or monitoring) we can do all
>>> changes
>>>>>>>> including tests as one commit within the main repository and
>>> don't
>>>>>> have
>>>>>>>> to
>>>>>>>> commit to main repo, sidecar repo,
>>>>>> 
>>>>>> I also don't see a reason why the sidecar being in tree means it
>>> would not
>>>>>> work in a mixed version cluster. The nodes themselves must work in a
>>> mixed
>>>>>> version cluster during a rolling upgrade, I would expect any
>>> management
>>>>>> side car to operate in the same manor, in tree or not.
>>>>>> 
>>>>>> This tool will be pretty tightly coupled with the server, and as
>>> someone
>>>>>> with experience developing such tightly coupled tools, it is *much*
>>> easier
>>>>>> to make sure you don't accidentally break them if they are in tree.
>>> How
>>>>>> many times has someone updated some JMX interface, updated nodetool,
>>> and
>>>>>> then moved on? Breaking all the external tools not in tree, without
>>>>>> realizing it. The above point about being able to modify interfaces
>>> and the
>>>>>> side car in the same commit is huge in terms of making sure someone
>>> doesn't
>>>>>> inadvertently break the side car while fixing something else.
>>>>>> 
>>>>>> -Jeremiah
>>>>>> 
>>>>>> 
>>>>>>> On Aug 21, 2018, at 10:28 AM, Jonathan Haddad <jon@jonhaddad.com>
>>>>>> wrote:
>>>>>>> 
>>>>>>> Strongly agree with Blake. In my mind supporting multiple versions
>>> is
>>>>>>> mandatory. As I've stated before, we already do it with Reaper, I'd
>>>>>>> consider it a major misstep if we couldn't support multiple with
>>> the
>>>>>>> project - provided admin tool. It's the same reason dtests are
>>> separate
>>>>>> -
>>>>>>> they work with multiple versions.
>>>>>>> 
>>>>>>> The number of repos does not affect distribution - if we want to
>>> ship
>>>>>>> Cassandra with the admin / repair tool (we should, imo), that can
>>> be
>>>>>> part
>>>>>>> of the build process.
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> On Mon, Aug 20, 2018 at 9:21 PM Blake Eggleston <
>>> beggleston@apple.com>
>>>>>>> wrote:
>>>>>>> 
>>>>>>>> If the sidecar is going to be on a different release cadence, or
>>>>>> support
>>>>>>>> interacting with mixed mode clusters, then it should definitely
>>> be in
>>>>>> a
>>>>>>>> separate repo. I don't even know how branching and merging would
>>> work
>>>>>> in a
>>>>>>>> repo that supports 2 separate release targets and/or mixed mode
>>>>>>>> compatibility, but I'm pretty sure it would be a mess.
>>>>>>>> 
>>>>>>>> As a cluster management tool, mixed mode is probably going to be
>>> a goal
>>>>>> at
>>>>>>>> some point. As a new project, it will benefit from not being
>>> tied to
>>>>>> the C*
>>>>>>>> release cycle (which would probably delay any sidecar release
>>> until
>>>>>>>> whenever 4.1 is cut).
>>>>>>>> 
>>>>>>>> 
>>>>>>>> On August 20, 2018 at 3:22:54 PM, Joseph Lynch (
>>> joe.e.lynch@gmail.com)
>>>>>> 
>>>>>>>> wrote:
>>>>>>>> 
>>>>>>>> I think that the pros of incubating the sidecar in tree as a tool
>>>>>> first
>>>>>>>> outweigh the alternatives at this point of time. Rough tradeoffs
>>> that
>>>>>> I
>>>>>>>> see:
>>>>>>>> 
>>>>>>>> Unique pros of in tree sidecar:
>>>>>>>> * Faster iteration speed in general. For example when we need to
>>> add a
>>>>>>>> new
>>>>>>>> JMX endpoint that the sidecar needs, or change something from
>>> JMX to a
>>>>>>>> virtual table (e.g. for repair, or monitoring) we can do all
>>> changes
>>>>>>>> including tests as one commit within the main repository and
>>> don't
>>>>>> have
>>>>>>>> to
>>>>>>>> commit to main repo, sidecar repo, and dtest repo (juggling
>>> version
>>>>>>>> compatibility along the way).
>>>>>>>> * We can in the future more easily move serious background
>>>>>> functionality
>>>>>>>> like compaction or repair itself (not repair scheduling, actual
>>>>>>>> repairing)
>>>>>>>> into the sidecar with a single atomic commit, we don't have to
>>> do two
>>>>>>>> phase
>>>>>>>> commits where we add some IPC mechanism to allow us to support
>>> it in
>>>>>>>> both,
>>>>>>>> then turn it on in the sidecar, then turn it off in the server,
>>> etc...
>>>>>>>> * I think that the verification is much easier (sounds like
>>> Jonathan
>>>>>>>> disagreed on the other thread, I could certainly be wrong), and
>>> we
>>>>>> don't
>>>>>>>> have to worry about testing matrices to assure that the sidecar
>>> works
>>>>>>>> with
>>>>>>>> various versions as the version of the sidecar that is released
>>> with
>>>>>> that
>>>>>>>> version of Cassandra is the only one we have to certify works. If
>>>>>> people
>>>>>>>> want to pull in new versions or maintain backports they can do
>>> that at
>>>>>>>> their discretion/testing.
>>>>>>>> * We can iterate and prove value before committing to a choice.
>>> Since
>>>>>> it
>>>>>>>> will be a separate artifact from the start we can always move the
>>>>>>>> artifact
>>>>>>>> to a separate repo later (but moving the other way is harder).
>>>>>>>> * Users will get the sidecar "for free" when they install the
>>> daemon,
>>>>>>>> they
>>>>>>>> don't need to take affirmative action to e.g. be able to restart
>>> their
>>>>>>>> cluster, run repair, or back their data up; it just comes out of
>>> the
>>>>>> box
>>>>>>>> for free.
>>>>>>>> 
>>>>>>>> Unique pros of a separate repository sidecar:
>>>>>>>> * We can use a more modern build system like gradle instead of
>>> ant
>>>>>>>> * Merging changes is less "scary" I guess (I feel like if you're
>>> not
>>>>>>>> touching the daemon this is already true but I could see this
>>> being
>>>>>> less
>>>>>>>> worrisome for some).
>>>>>>>> * Releasing a separate artifact is somewhat easier from a
>>> separate
>>>>>> repo
>>>>>>>> (especially if we have gradle which makes e.g. building debs and
>>> rpms
>>>>>>>> trivial).
>>>>>>>> * We could backport to previous versions without getting into
>>>>>> arguments
>>>>>>>> about bug fixes vs features.
>>>>>>>> * Committers could be different from the main repo, which ...
>>> may be a
>>>>>>>> useful thing
>>>>>>>> 
>>>>>>>> Non unique pros of a sidecar (could be achieved in the main repo
>>> or in
>>>>>> a
>>>>>>>> separate repo):
>>>>>>>> * A separate build artifact .jar/.deb/.rpm that can be installed
>>>>>>>> separately. It's slightly easier with a separate repo but
>>> certainly
>>>>>> not
>>>>>>>> out
>>>>>>>> of reach within a single repo (indeed the current patch already
>>> creates
>>>>>> a
>>>>>>>> separate jar, and we could create a separate .deb reasonably
>>> easily).
>>>>>>>> Personally I think having a separate .deb/.rpm is premature at
>>> this
>>>>>> point
>>>>>>>> (for companies that really want it they can build their own
>>> packages
>>>>>>>> using
>>>>>>>> the .jars), but I think it really is a distracting issue from
>>> where
>>>>>> the
>>>>>>>> patch should go as we can always choose to remove experimental
>>> .jar
>>>>>> files
>>>>>>>> that the main daemon doesn't touch.
>>>>>>>> * A separate process lifecycle. No matter where the sidecar
>>> goes, we
>>>>>> get
>>>>>>>> the benefit of restarting it being less dangerous for
>>> availability
>>>>>> than
>>>>>>>> restarting the main daemon.
>>>>>>>> 
>>>>>>>> That all being said, these are strong opinions weakly held and I
>>> would
>>>>>>>> rather get something actually committed so that we can prove
>>> value one
>>>>>>>> way
>>>>>>>> or the other and am therefore, of course, happy to put sidecar
>>> patches
>>>>>>>> wherever someone can review and commit it.
>>>>>>>> 
>>>>>>>> -Joey
>>>>>>>> 
>>>>>>>> On Mon, Aug 20, 2018 at 1:52 PM sankalp kohli <
>>> kohlisankalp@gmail.com>
>>>>>> 
>>>>>>>> wrote:
>>>>>>>> 
>>>>>>>>> Hi,
>>>>>>>>> I am starting a new thread to get consensus on where the side
>>> car
>>>>>>>>> should be contributed.
>>>>>>>>> 
>>>>>>>>> Please send your responses with pro/cons of each approach or
>>> any
>>>>>> other
>>>>>>>>> approach. Please be clear which approach you will pick while
>>> still
>>>>>>>> giving
>>>>>>>>> pros/cons of both approaches.
>>>>>>>>> 
>>>>>>>>> Thanks.
>>>>>>>>> Sankalp
>>>>>>>>> 
>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> --
>>>>>>> Jon Haddad
>>>>>>> http://www.rustyrazorblade.com
>>>>>>> twitter: rustyrazorblade
>>>>>> 
>>>>>> 
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>>>>>> 
>>>>>> 
>>>> 
>>>> 
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>>>> 
>>> 
> 
> 
> 
> -- 
> Eric Evans
> john.eric.evans@gmail.com
> 
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