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0807e3e2f7
The Windows CI machine experiences significant random execution delays.
For example, in this code from watchdog.go:
done := make(chan bool)
go func() {
start := time.Now()
mu.Lock()
There was a 500ms delay from initializing done to locking mu.
This test checks that we receive a sufficient number of events quickly enough.
In the face of random 500ms delays, unsurprisingly, the test fails.
There's not much principled we can do about it.
We could build a system of retries or attempt to detect these random delays,
but that game isn't worth the candle.
Skip the test.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
81 lines
2.2 KiB
Go
81 lines
2.2 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package syncs
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import (
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"context"
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"runtime"
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"sync"
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"testing"
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"time"
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"tailscale.com/util/cibuild"
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)
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// Time-based tests are fundamentally flaky.
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// We use exaggerated durations in the hopes of minimizing such issues.
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func TestWatchUncontended(t *testing.T) {
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mu := new(sync.Mutex)
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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// Once an hour, and now, check whether we can lock mu in under an hour.
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tick := time.Hour
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max := time.Hour
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c := Watch(ctx, mu, tick, max)
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d := <-c
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if d == max {
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t.Errorf("uncontended mutex did not lock in under %v", max)
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}
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}
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func TestWatchContended(t *testing.T) {
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mu := new(sync.Mutex)
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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// Every hour, and now, check whether we can lock mu in under a millisecond,
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// which is enough time for an uncontended mutex by several orders of magnitude.
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tick := time.Hour
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max := time.Millisecond
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mu.Lock()
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defer mu.Unlock()
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c := Watch(ctx, mu, tick, max)
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d := <-c
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if d != max {
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t.Errorf("contended mutex locked in under %v", max)
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}
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}
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func TestWatchMultipleValues(t *testing.T) {
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if cibuild.On() && runtime.GOOS == "windows" {
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// On the CI machine, it sometimes takes 500ms to start a new goroutine.
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// When this happens, we don't get enough events quickly enough.
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// Nothing's wrong, and it's not worth working around. Just skip the test.
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t.Skip("flaky on Windows CI")
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}
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mu := new(sync.Mutex)
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel() // not necessary, but keep vet happy
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// Check the mutex every millisecond.
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// The goal is to see that we get a sufficient number of values out of the channel.
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tick := time.Millisecond
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max := time.Millisecond
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c := Watch(ctx, mu, tick, max)
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start := time.Now()
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n := 0
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for d := range c {
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n++
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if d == max {
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t.Errorf("uncontended mutex did not lock in under %v", max)
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}
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if n == 10 {
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cancel()
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}
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}
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if elapsed := time.Since(start); elapsed > 100*time.Millisecond {
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t.Errorf("expected 1 event per millisecond, got only %v events in %v", n, elapsed)
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}
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}
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