tailscale/syncs/watchdog_test.go

78 lines
2.0 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package syncs
import (
"context"
"runtime"
"sync"
"testing"
"time"
)
// Time-based tests are fundamentally flaky.
// We use exaggerated durations in the hopes of minimizing such issues.
func TestWatchUncontended(t *testing.T) {
mu := new(sync.Mutex)
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
// Once an hour, and now, check whether we can lock mu in under an hour.
tick := time.Hour
max := time.Hour
c := Watch(ctx, mu, tick, max)
d := <-c
if d == max {
t.Errorf("uncontended mutex did not lock in under %v", max)
}
}
func TestWatchContended(t *testing.T) {
mu := new(sync.Mutex)
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
// Every hour, and now, check whether we can lock mu in under a millisecond,
// which is enough time for an uncontended mutex by several orders of magnitude.
tick := time.Hour
max := time.Millisecond
mu.Lock()
defer mu.Unlock()
c := Watch(ctx, mu, tick, max)
d := <-c
if d != max {
t.Errorf("contended mutex locked in under %v", max)
}
}
func TestWatchMultipleValues(t *testing.T) {
mu := new(sync.Mutex)
ctx, cancel := context.WithCancel(context.Background())
defer cancel() // not necessary, but keep vet happy
// Check the mutex every millisecond.
// The goal is to see that we get a sufficient number of values out of the channel.
tick := time.Millisecond
max := time.Millisecond
c := Watch(ctx, mu, tick, max)
start := time.Now()
n := 0
for d := range c {
n++
if d == max {
t.Errorf("uncontended mutex did not lock in under %v", max)
}
if n == 10 {
cancel()
}
}
// See https://github.com/golang/go/issues/44343 - on Windows the Go runtime timer resolution is currently too coarse. Allow longer in that case.
want := 100 * time.Millisecond
if runtime.GOOS == "windows" {
want = 500 * time.Millisecond
}
if elapsed := time.Since(start); elapsed > want {
t.Errorf("expected 1 event per millisecond, got only %v events in %v", n, elapsed)
}
}