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From Jan Lehnardt <>
Subject Re: [PROPOSAL] Improving the quality of CouchDB
Date Thu, 10 Sep 2015 16:38:57 GMT

> On 10 Sep 2015, at 18:31, Robert Kowalski <> wrote:
> Hi Jan,
> how would testing of a PR/change work in practice?
> Example: I am opening 3 Pull-Requests that depend on each other, one in
> chttpd, one in fabric and one in rexi.
> Or is the idea that the testsuite turns red when the deps are updated in
> the top level module?

Yeah, if the top module only works with all three PRs in concert, you get two broken builds
and then a working build.

(some of the details of what I explained earlier might make it sound that this isn’t possible,
rest assured, we’ve considered this case :)


> On Thu, Sep 10, 2015 at 2:09 PM, Jan Lehnardt <> wrote:
>>> On 10 Sep 2015, at 12:18, Alexander Shorin <> wrote:
>>> On Thu, Sep 10, 2015 at 12:40 PM, Dale Harvey <>
>> wrote:
>>>> I dont think CI is a dream, It should take an afternoon at most to get
>>>> CouchDB setup on travis on a single platform to ensure no major
>> regressions
>>>> come though. If anyone wants help doing that feel free to ping me on
>>>> #pouchdb / #couchdb, we already test couchdb master in travis.
>>> It is a dream for now.
>>> We have travis enabled, but it has practical flaw: it cannot handle
>>> changes that affected multiple repositories at the same time. Also,
>>> for each repository we have to build full CouchDB to test what is a
>>> bit overkill.
>>>> I do think multirepos is an issue and that solution is not so simple, we
>>>> went through the same issues with pouchdb as we attempted to split out
>> our
>>>> repository.
>>> Well, there was a good theory that each of our repository will contain
>>> an app which could be reused outside of CouchDB or being easily
>>> replaced by alternative implementation. Suddenly, for now most of our
>>> apps are heavy coupled
>> There are two distinct functions that git does for us here:
>> 1. Separate code into different modules.
>> 2. Make a module available to downstream users.
>> In a Node/npm, Python/pip, Ruby/Gems world, 1. is solved by git, 2. is
>> solved by npm/pip/Gems. Is there a way to publish an Erlang module for
>> downstream users
>> independently of git? If yes, we could move back to a single-git-tree
>> model for
>> CouchDB, but we can still release parts as independent modules. I know
>> there have
>> been a few attempts at Erlang package managers, but has anything taken off?
>> * * *
>> For Hoodie, we came up with this, based on our experience with using the
>> full top level test suite on each module (it is indeed overkill):
>> - separate modules
>> - one module that is the top level module (like our couchdb.git) that only
>> includes module dependencies and a top-level integration test suite.
>> - two release trains: stable and next.
>> - a service that attempts to create a new version of the top level module
>> with every commit to a dependent module. E.g. we automatically bump the
>> dependency in a checkout of the top level module, run the integration
>> tests, if they fail, nothing happens and we report that back on the commit
>> to the dependent module. If it succeeds, we automatically determine the
>> next version number on the next release train (SemVer makes that easy) and
>> release the new top level module with the updated dependency.
>> - once we are comfortable that the next release train is stable enough for
>> a release, we change switch out the release trains: next becomes stable,
>> and we have a new empty next train (npm uses release tags for this, but the
>> mechanics are irrelevant, although something like that needs to be
>> supported in the package manager).
>> This requires:
>> - Strict SemVer on all modules (we use
>> to make sure humans
>> can’t screw this up.
>> - Breaking change detection, so we don’t accidentally release a BC break
>> in a non-major version (available as semantic-release plugins).
>> - the service that does the auto-update dance described above.
>> This is a lot of infrastructure (and some of it we are still developing),
>> but once in place, it is really simple to not screw this up and it takes a
>> huge cognitive load off of everyday development.
>> Semantic-Release is language agnostic in theory, but afaik there are only
>> Node and Python versions, so we’d have to find someone to make an Erlang
>> variant. Also, the process uses npm heavily, so some sort of package
>> management system would be nice.
>> Eventually, I’d love to see this for CouchDB.
>> PS: The person who invented semantic-release works for my company, and I’d
>> be more than happy to have them have a crack at this. If anyone wants to
>> sponsor an erlang-semantic-release, please get in touch.
>> * * *
>> Either way, this is a bit of a long shot. For now:
>> We should do what Dale proposed in 2.: pin top level dependencies. I
>> believe that was the plan all along, but with a fast moving 2.0 we just
>> didn’t do it yet. Now is the time to pin versions and manually upgrade them
>> after thorough testing (can still be in PRs and tested on Travis and
>> everything).
>> That means all of these modules (and their sub-deps) should get releases
>> and release tags and those tags need to be filled into our top-level
>> rebar.config.script:
>> Let’s get going :)
>> Thanks
>> Jan
>> --
>>>> 1. Dont split out into lots of repositories, if you put those components
>>>> inside the CouchDB repo, then they will get the CouchDB tests run
>> against
>>>> them when changes are made and you wont break the CouchDB repo.
>>> It's good in retrospective, but useless now. We have to decide how our
>>> CI will work: with multirepo layout or first fold all core repos back
>>> to the one. I think we are ready to revise this too and probably this
>>> should be done before CI work.
>>>> 2. Anything that does live outside the CouchDB repo, pin their version
>>>> inside the CouchDB repo, dont have commits to subproject X
>> automatically be
>>>> applied to CouchDB, that means you can commit whatever you want to X but
>>>> CouchDB will still be working, when you come to update the version of X
>> you
>>>> pinned, you can see that it breaks and not update until it is fixed.
>>> It's good strategy for milestones or when you don't have to manage 40+
>> repos (:
>>>> 2.5 Another strategy that can help with this is to have the full
>> CouchDB
>>>> test suite run inside X, so changes to X will run the full CouchDB suite
>>>> with an updated X
>>> This works, but until changes are belongs to a single repository. See
>>> above about travis issue.
>>> P.S. Jason, you are right again (:
>>> --
>>> ,,,^..^,,,
>> --
>> Professional Support for Apache CouchDB:

Professional Support for Apache CouchDB:

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