>How about splitting the unnamed version into explicit v0, v2, and internal?

Currently our internal protobuf and v0 protobuf use the same unnamed
version protobuf and under the same namespace (`package mesos`).
If we are going to split v0 and internal, that requires copy all protobuf
files under `package mesos` into `package mesos.internal` and need to
change the whole code base to use the protobuf in `package mesos.internal`.
But it is beneficial to do this, so that we could avoid [the hacks][1]
that convert from the unversioned protobuf(v0) to the unversioned


On Thu, Oct 13, 2016 at 12:34 AM, Alex Rukletsov <a...@mesosphere.com>

> Folks,
> There have been a bunch of online [1, 2] and offline discussions about our
> deprecation and versioning policy. I found that people—including
> myself—read the versioning doc [3] differently; moreover some aspects are
> not captured there. I would like to start a discussion around this topic by
> sharing my confusions and suggestions. This will hopefully help us stay on
> the same page and have similar expectations. The second goal is to
> eliminate ambiguities from the versioning doc (thanks Vinod for
> volunteering to update it).
> 1. API vs. semantic changes.
> Current versioning guide treat features (e.g. flags, metrics, endpoints)
> and API differently: incompatible changes for the former are allowed after
> 6 month deprecation cycle, while for the latter they require bumping a
> major version. I suggest we consolidate these policies.
> We should also define and clearly explain what changes require bumping the
> major version. I have no strong opinion here and would love to hear what
> people think. The original motivation for maintaining backwards
> compatibility is to make sure vN schedulers can correctly work with vN API
> without being updated. But what about semantic changes that do not touch
> the API? For example, what if we decide to send less task health updates to
> schedulers based on some health policy? It influences the flow of task
> status updates, should such change be considered compatible? Taking it to
> an extreme, we may not even be able to fix some bugs because someone may
> already rely on this behaviour!
> Another tightly related thing we should explicitly call out is
> upgradability and rollback capabilities inside a major release. Committing
> to this may significantly limit what we can change within a major release;
> on the other side it will give users more time and a better experience
> about using and maintaining Mesos clusters.
> 2. Versioned vs. unversioned protobufs.
> Currently we have v1 and unnamed protobufs, which simultaneously mean v0,
> v2, and internal. I am sometimes confused about what is the right way to
> update or introduce a field or message there, do people feel the same? How
> about splitting the unnamed version into explicit v0, v2, and internal?
> Food for thought. It would be great if we can only maintain "diffs" to the
> internal protobufs in the code, instead of duplicating them altogether.
> 3. API and feature labelling.
> I suggest to introduce explicit labels for API and features, to ensure
> users have the right assumptions about the their lifetime while engineers
> have the ability to change a wip feature in an non-compatible way. I
> propose the following:
> API: stable, non-stable, pure (not used by Mesos components)
> Feature: experimental, normal.
> Looking forward to your thoughts and suggestions.
> AlexR
> [1] https://www.mail-archive.com/user@mesos.apache.org/msg08025.html
> [2] https://www.mail-archive.com/dev@mesos.apache.org/msg36621.html
> [3]
> https://github.com/apache/mesos/blob/b2beef37f6f85a8c75e968136caa7a
> 1f292ba20e/docs/versioning.md

Best Regards,
Haosdent Huang

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