server,rpc,circuit: assortment of small cleanups/improvements

[tbg]

Extracted from #99191.

• server: fix a (harmless) test buglet
• rpc: small comment tweak
• rpc: fix incorrect comment
• circuit: provide type for the anonymous Signal interface
• rpc: rename a package
• rpc: minor Goland lint appeasement
• rpc: avoid shadowing backoff package
• rpc: make some unused args anonymous
• rpc: make it clear that TestStoreMetrics restarts stores

Release note: None
Epic: None

[cockroach-teamcity]

This change is 

[knz]

LGTM but I thought you wanted to use the prev error somewhere?

Reviewed 1 of 1 files at r1, 1 of 1 files at r2, 1 of 1 files at r3, 1 of 1 files at r4, 4 of 4 files at r5, 1 of 1 files at r6, 1 of 1 files at r7, 3 of 3 files at r8, 2 of 2 files at r9, 1 of 1 files at r10, all commit messages.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @aliher1911 and @tbg)

---

pkg/util/circuit/circuitbreaker.go line 153 at r5 (raw file):

// Outside of testing, there should be no reason to call this
// as it is the probe's job to reset the breaker if appropriate.
func (b *Breaker) Reset() {

Slightly easier on the eye:

var prev error
defer func() { b.Opts().EventHandler.OnReset(b, prev) }()

b.mu.Lock()
defer b.mu.Unlock()
if wasTripped := b.mu.errAndCh.err != nil; wasTripped {
  prev = b.mu.errAndCh.err
  b.mu.errAndCh = b.newErrAndCh()
}

---

pkg/util/circuit/event_handler.go line 66 at r5 (raw file):

func (d *EventLogger) OnReset(breaker *Breaker, prev error) {
	var buf redact.StringBuilder
	EventFormatter{}.OnReset(breaker, &buf)

Not using prev here?

[tbg]

TFTR!

I decided to drop the commit you were working on. I originally anticipated using a custom event handler in #99191 but this didn't materialize, so the new code would be unused. (I don't think it's useful for the default impl of EventHandler to log the previous error when the breaker resets).

[tbg]

bors r=knz
TFTR!

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)