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

It's a small library whose benefits don't overweight the drawbacks.
Any additional dependency crate makes the build slower. But itertools in
particular is harmful because it hides some expensive computations
behind simple tempting to use functions such as `sorted_by`.

Also prefix stored procedures names `raft_join` and `raft_interact`

If proc_discover is invoked after raft node was initialized but before
raft leader was elected, it would return an error before this commit.
Because of that it was impossible to restart the whole cluster at once.

This commit change proc_discover such that in case leader_id is not
ready, the normal discovery algorithm takes place.

Closes #93

Previously the discovery algorithm would try to reach each known peer
sequentially requiring each consequent request to succeed until the next
one can be attempted. This would not work in some cases (see test in
previous commit).

So the new algorithm instead makes a single attempt to reach each peer
within a round, and if some failed they're retried in the next round of
requests. This allows overall discovery to succeed in cases when some
of the initial peers never respond.

Closes #54

```console
$ cargo clippy
   Compiling picodata v0.1.0 (/home/rosik/w/picodata)
warning: 'tarantool-sys/patches-applied' exists, so patching step is
skipped
warning: single-character string constant used as pattern
   --> src/args.rs:194:47
    |
194 |     let (host, port) = match text.rsplit_once(":") {
    |                                               ^^^ help: try using
a `char` instead: `':'`
    |
    = note: `#[warn(clippy::single_char_pattern)]` on by default
    = help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#single_char_pattern

warning: called `cloned().next()` on an `Iterator`. It may be more
efficient to call `next().cloned()` instead
   --> src/discovery.rs:154:27
    |
154 |                 let res =
    peers.difference(&self.visited).cloned().next();
    |
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this:
`peers.difference(&self.visited).next().cloned()`
    |
    = note: `#[warn(clippy::iter_overeager_cloned)]` on by default
    = help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#iter_overeager_cloned

warning: you seem to be trying to use `match` for destructuring a single
pattern. Consider using `if let`
  --> src/ipc.rs:27:9
   |
27 | /         match rmp_serde::encode::write(&mut self.fd, msg) {
28 | |             Err(e) => tlog!(Error, "ipc error: {e}"),
29 | |             Ok(()) => (),
30 | |         }
   | |_________^ help: try this: `if let Err(e) =
rmp_serde::encode::write(&mut self.fd, msg) { tlog!(Error, "ipc error:
{e}") }`
   |
   = note: `#[warn(clippy::single_match)]` on by default
   = help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#single_match

warning: `picodata` (bin "picodata") generated 3 warnings
    Finished dev [unoptimized + debuginfo] target(s) in 1.41s
```

Since dynamic discovery isn't implemented yet, instance after
`raft_join` has discovery uninitialized. It's not a reason to panic.

This pach establishes a friendship between discovery and raft_join.