No assumptions should be made on `traft::node::Status.leader_id`. It can
be set to `None` at any time due to a re-election.

Cases covered:
- when someone goes offline
- whenever vshard gets reconfigured

Georgy Moshkin authored 2 years ago and Georgy Moshkin committed 2 years ago

Currently stores:
- replicset_id
- replicaset_uuid
- sharding weight
- replication master id

Yaroslav Dynnikov authored 2 years ago and Yaroslav Dynnikov committed 2 years ago

Only a few functions are allowed in signal handlers (see `man 7
signal-safety`). Both `println!()` and `std::process::exit()` are not
acceptable. In our case `std::process::exit()` resulted in a dead lock
when called concurrently.

This patch fixes it, and also enhances some other aspects of the supervisor.

See also: https://stackoverflow.com/questions/44865737/println-panics-when-called-concurrently

Yaroslav Dynnikov authored 2 years ago and Yaroslav Dynnikov committed 2 years ago

This commit slignly changes the order of entries in the raft log:
ConfChange now comes at the first place before other Ops, but that's ok.

Yaroslav Dynnikov authored 2 years ago and Yaroslav Dynnikov committed 2 years ago

Do it only when the governor tells to. When `_G.vshard == nil`, it's
more alike `traft::node::global()` which reurns either `Ok` or
`Err(Uninitialized)`.

Yaroslav Dynnikov authored 2 years ago and Yaroslav Dynnikov committed 2 years ago

It produces better error messages.

Before this commit:

```
tarantool> vshard.router.call()
---
- error: '[string "local log = require(''log'')..."]:575: attempt to
    compare number with nil'
...
```

With this commit:

```
- error: 'vshard/router/init.lua:575: attempt to compare number with
    nil'
```

Example:

```console
tarantool> picolib.whoami()
---
- raft_id: 1
  cluster_id: demo
  instance_id: i1
...

tarantool> picolib.peer_info("i1")
---
- raft_id: 1
  instance_id: i1
  instance_uuid: 68d4a766-4144-3248-aeb4-e212356716e4
  replicaset_uuid: e0df68c5-e7f9-395f-86b3-30ad9e1b7b07
  replicaset_id: r1
  advertise_address: localhost:3301
  target_grade: Online
  current_grade: Online
...
```