Reduce some internal panics.

[Hoverbear]

The Raft library has several internal panics. This is partially due to being fairly old code with Go origins, and partially due to it being previously internal to TiKV.

This issue, broadly, invites you to tackle any panic!() or .unwrap() you find in the library.

Notable targets to get you started:

• fn insert_learner in src/raft.rs.
• fn insert_voter in src/raft.rs.

You are welcome to tackle any potential panics though. Please link them back to this issue for overall tracking.

Your PR may take some time to merge as we would like to stage public API changes. The next targeted API change is in 0.5.0.

[JoshMcguigan]

It looks like fn insert_learner and fn insert_voter both return a Result at this time. At a quick glance, the only way for them to panic would be for the assert_eq check in fn assert_progress_and_configuration_consistent to fail.

Did you want to add a ProgressConfigurationInconsistent error type and return that rather than panic? Or can this issue be marked as resolved for those two methods?

I'd be interested in taking a look at this issue, if you have any guidance on a particular panic! or unwrap which would be a good candidate for removal (assuming the two methods above should be marked as done).

[Hoverbear]

Hi @JoshMcguigan You're right. I think this has been fixed, actually! :( Darnit!