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tailscale/syncs/watchdog_test.go

81 lines
2.2 KiB
Go

// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package syncs
import (
"context"
"runtime"
"sync"
"testing"
"time"
"tailscale.com/util/cibuild"
)
// 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) {
if cibuild.On() && runtime.GOOS == "windows" {
// On the CI machine, it sometimes takes 500ms to start a new goroutine.
// When this happens, we don't get enough events quickly enough.
// Nothing's wrong, and it's not worth working around. Just skip the test.
t.Skip("flaky on Windows CI")
}
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()
}
}
if elapsed := time.Since(start); elapsed > 100*time.Millisecond {
t.Errorf("expected 1 event per millisecond, got only %v events in %v", n, elapsed)
}
}