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From Chris Hillery <chill...@lambda.nu>
Subject Re: Migration of git repository
Date Tue, 02 Jun 2015 17:00:44 GMT
On Mon, Jun 1, 2015 at 9:46 PM, Yingyi Bu <buyingyi@gmail.com> wrote:

> In my opinion,  merging the repository doesn't break the separation of
> hyracks and asterixdb, because the dependencies are controlled by mvn pom
> files.
>

That wasn't the separation I was talking about. I meant API separation. As
it is now, when we make a change to both Asterix and Hyracks, we are forced
to consider the API implications, or at least they are put out there in a
very clear way that we need to look at. If we merge them, people will
(rightly) treat the whole thing as one product, and there will be no brakes
on making wide-ranging API changes.

(As an aside: I don't trust Maven's pom files to do a good job of keeping
the dependency management clean. In fact I trust it to do precisely the
opposite, by making it both easier to screw up the dependencies and harder
to update them in future.)

Again, my point is this: If we truly believe that Hyracks is a re-usable
component, it should be treated as such from source to build to delivery.
By merging in Asterix, we are saying that Asterix is "more equal" than
others Hyracks clients, to the point that we're tacitly willing to break
those other clients in favor of simplifying Asterix development. If that is
a fair and true statement, well, then, sure, let's merge them.

1) It forces those hyracks-only changes to pass asterixdb regression
> tests.  Currently hyracks-only change are not verified by asterixdb tests.
>

This is a good point, I will admit. However, I think this same goal can be
met in other ways. My strong preference would be to create a set of true
API tests inside of Hyracks, which both document and test the external
Hyracks API. That will make API-breaking changes in future much easier to
spot, and also make it clear when Asterix is using internal APIs that it
should not.


> 2) On my local machine,  I don't need to always install hyracks and then
> verify asterixdb from time to time.  Especially, switching branches seems
> painful because the installed hyracks snapshot is overwritten from time to
> time.
>

I haven't tried working on multiple Hyracks branches at the same time, so I
haven't experienced this. This seems like a working method error, though.
If you're working with two things that are "the same version" (even if
that's a snapshot version), you'll need to use separate Maven repositories
to install them. In fact, merging the two git repositories would do nothing
to fix this problem, will it? If the proposal is to put the two source
repositories in the same git repo but otherwise leave them untouched, then
nothing would change in the build process. It's possible I'm missing
something there, though.


> 3) I only need to make one code review request and one jenkins job.
> Currently I need to manually change the topic of my asterixdb gerrit CL
> every time before I update my hyracks CL, and then manually schedule
> jenkins to run a new asterixdb job.  If I forget to schedule the jenkins
> job, the asterixdb CL is still shown to be "verified by jenkins".
>

This is a problem, but it's a problem in commit validation, not in the
source. Modifying the source to work around these issues is still a bad
idea IMHO.

The "change-topic" issue could be fixed with a bit of development work
(have the topic point to a change, rather than a specific patchset on the
change, so you only need to set it once, for instance).

As for manually scheduling Asterix Jenkins jobs, that sounds like it's only
a problem where your Hyracks change breaks an existing public API. That
would be obviated by having true API testing inside of Hyracks, which is
something that we should have regardless of any decisions about source
locations.

In summary / repeating myself again: yes, we have some problems because
Hyracks and Asterix are in seperate repositories. But those problems are
pointing out true issues with our development and processes. Merging the
repositories isn't fixing those problems, it's sweeping them under the rug.
Long term we would be much better off to identify, isolate, and fix the
problems themselves.

Ceej
aka Chris Hillery

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