Porting prost migration to raft 0.4

[ice1000]

For TiKV usages.
This is opened as a PR only for code review, please don't merge.

Currently there's one assertion error in tests but the production code are (seem to) working.

[ice1000]

The assertion error is in
https://github.com/pingcap/raft-rs/blob/26f51c2e64c07967d86d15b4da716f28ea374567/tests/integration_cases/test_raft.rs#L2308

[nrc]

The assertion error is in ...

On master this is assert_eq!(rs.index, 2);. I wonder if there is a rebasing error?

[nrc]

LGTM

[Hoverbear]

Seems it would be good if we made a branch off 0.4.1 and then merged this with that, then we can release 0.4.2 from that branch?

[ice1000]

@Hoverbear sounds good to me!

[Hoverbear]

Seems we never released 0.4.1, so we'll make this 0.4.1. :)

[Hoverbear]

Rest LGTM, please fix some of the nits though :)

[ice1000]

All comments addressed except those depends on tikv/protobuf-build#3.

[CLAassistant]

All committers have signed the CLA.

[ice1000]

@nrc PTAL at the CLA

[nrc]

I think this just needs the protobuf-build update and then can be merged

[ice1000]

Comments related to tikv/protobuf-build#3 are addressed.

[nrc]

Failing tests now :-(

[Hoverbear]

Forcing a rebuild on CI

[ice1000]

I have one test failing locally but I didn't know why (at least seem to be unrelated to pb library).

[ice1000]

It's supposed to be fixed now. Let's wait for CI response...

[nrc]

Still some errors, looks like lints

[nrc]

@ice1000 can you pull in #219 to fix the CI please?

[ice1000]

All comments addressed. Mr. Travis CI, please start your performance

[ice1000]

error: the feature `tool_lints` has been stable since 1.31.0 and no longer requires an attribute to enable
   --> src/lib.rs:264:47
    |
264 | #![cfg_attr(feature = "cargo-clippy", feature(tool_lints))]
    |                                               ^^^^^^^^^^
    |
    = note: `-D stable-features` implied by `-D warnings`
error: this .into_iter() call is equivalent to .iter() and will not move the slice
   --> src/raft.rs:789:14
    |
789 |         ents.into_iter()
    |              ^^^^^^^^^ help: call directly: `iter`
    |
    = note: `-D clippy::into-iter-on-ref` implied by `-D clippy::all`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#into_iter_on_ref
error: aborting due to 2 previous errors

[ice1000]

I don't understand. I can see a lot of stacktraces in the nightly CI build, but it's saying test all passed.
Is that what we expect to see?

[ice1000]

Yay! CI passed!

[nrc]

@Hoverbear can we release this as 0.4.1 please?

[Hoverbear]

Sorry about the delay @ice1000 :(

[ice1000]

No problem, I can totally understand that you people are busy last week!

[BusyJay]

This PR introduces API changes, and should be landed on 0.5.x instead of 0.4.x.

[Hoverbear]

@BusyJay Prior to 1.0.0 authors are free to break API as they please. 0.5.0 contains other changes and is already released. It's incompatible with TiKV.

[ice1000]

@BusyJay We have another PR that does the same thing but based on the master branch instead of the 0.4.0 release tag.

[nrc]

Discussed on Slack, we agreed to yank 0.4.1 and use Prost via a Git dep for the time being