Riak versions - 3.1.0

[martinsumner]

Some initial work has started on OTP 24 compatibility, sparked by potential interest in testing the impact of JIT compilation.

The policy of rebar3 which we depend on is to only support three OTP versions. Currently for 3.0.n we support OTP 20 - 22, with a disclaimer that the focus of testing for migration is on OTP 20 and testing for performance is on OTP 22, and little direct testing of OTP 22 is undertaken.

Proposal here is that for Riak 3.1.0, we should support OTP 22 - OTP 24, and although that range includes OTP 23, the actual testing activity will be restricted to OTP 22 and OTP 24. Restricting the versions this way is helpful with managing dependencies, but also with the effort required to test and package each release.

If there are objections to this, please shout out.

[Bob-The-Marauder]

That seems fair enough to me.

For the record, the packages are currently built on OTP 20.3 and OTP 22.3. Once the OTP 24 subversion is decided, packages will be built in that version accordingly.

If Riak 3.1.0 is going to be OTP 22 - OTP 24, how does this work for upgrading users? Will the OTP 22 version again be for upgrade and the OTP 24 version focused on performance? If a user uses Riak KV 3.0.x on OTP 20.3, will they be able to upgrade to Riak KV 3.1.0 OTP 24 direct or do they have to go via an OTP 22 iteration first? In that case would it be via Riak KV 3.0.x OTP 22 or Riak KV 3.1.0 OTP 22?

[martinsumner]

The current test setup we've not experimented with mixed OTP version tests, so I'm a touch reticent to make bold promises about mixing and matching Riak and OTP versions.

However, there's no obvious reason why running mixed clusters should not work, it is just a question of whether that will be proven before release.

[martinsumner]

I think also when I say OTP 22 -> 24, this in reality may mean OTP 22.3 or OTP 24.3 (or whatever the latest 24 minor version is available at the point we're ready).