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author | Bryan C. Mills <bcmills@google.com> | 2020-03-30 14:04:08 -0400 |
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committer | Bryan C. Mills <bcmills@google.com> | 2020-03-31 17:59:03 +0000 |
commit | 5d2ddcd3f51c1ff7aa0a84604b1d8610a17a7933 (patch) | |
tree | ee5d94a3252af4b9503728f979a6d21dc9759627 /src/context | |
parent | 5db079d2e5f97952be288c28a3a0690a523efdce (diff) | |
download | go-5d2ddcd3f51c1ff7aa0a84604b1d8610a17a7933.tar.gz go-5d2ddcd3f51c1ff7aa0a84604b1d8610a17a7933.zip |
context: fix a flaky timeout in TestLayersTimeout
In CL 223019, I reduced the short timeout in the testLayers helper to
be even shorter than it was. That exposed a racy (time-dependent)
select later in the function, which failed in one of the slower
builders (android-386-emu).
Also streamline the test to make it easier to test with a very high -count flag:
- Run tests that sleep for shortDuration in parallel to reduce latency.
- Use shorter durations in examples to reduce test running time.
- Avoid mutating global state (in package math/rand) in testLayers.
After this change (but not before it),
'go test -run=TestLayersTimeout -count=100000 context' passes on my workstation.
Fixes #38161
Change-Id: Iaf4abe7ac308b2100d8828267cda9f4f8ae4be82
Reviewed-on: https://go-review.googlesource.com/c/go/+/226457
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Diffstat (limited to 'src/context')
-rw-r--r-- | src/context/context_test.go | 27 | ||||
-rw-r--r-- | src/context/example_test.go | 6 |
2 files changed, 22 insertions, 11 deletions
diff --git a/src/context/context_test.go b/src/context/context_test.go index 98c6683335..6b392a29da 100644 --- a/src/context/context_test.go +++ b/src/context/context_test.go @@ -27,6 +27,7 @@ type testingT interface { Log(args ...interface{}) Logf(format string, args ...interface{}) Name() string + Parallel() Skip(args ...interface{}) SkipNow() Skipf(format string, args ...interface{}) @@ -284,6 +285,8 @@ func testDeadline(c Context, name string, t testingT) { } func XTestDeadline(t testingT) { + t.Parallel() + c, _ := WithDeadline(Background(), time.Now().Add(shortDuration)) if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) { t.Errorf("c.String() = %q want prefix %q", got, prefix) @@ -307,6 +310,8 @@ func XTestDeadline(t testingT) { } func XTestTimeout(t testingT) { + t.Parallel() + c, _ := WithTimeout(Background(), shortDuration) if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) { t.Errorf("c.String() = %q want prefix %q", got, prefix) @@ -417,9 +422,9 @@ func XTestAllocs(t testingT, testingShort func() bool, testingAllocsPerRun func( gccgoLimit: 3, }, { - desc: "WithTimeout(bg, 15*time.Millisecond)", + desc: "WithTimeout(bg, 1*time.Nanosecond)", f: func() { - c, _ := WithTimeout(bg, 15*time.Millisecond) + c, _ := WithTimeout(bg, 1*time.Nanosecond) <-c.Done() }, limit: 12, @@ -545,7 +550,9 @@ func XTestLayersTimeout(t testingT) { } func testLayers(t testingT, seed int64, testTimeout bool) { - rand.Seed(seed) + t.Parallel() + + r := rand.New(rand.NewSource(seed)) errorf := func(format string, a ...interface{}) { t.Errorf(fmt.Sprintf("seed=%d: %s", seed, format), a...) } @@ -560,7 +567,7 @@ func testLayers(t testingT, seed int64, testTimeout bool) { ctx = Background() ) for i := 0; i < minLayers || numTimers == 0 || len(cancels) == 0 || len(vals) == 0; i++ { - switch rand.Intn(3) { + switch r.Intn(3) { case 0: v := new(value) ctx = WithValue(ctx, v, v) @@ -587,10 +594,12 @@ func testLayers(t testingT, seed int64, testTimeout bool) { } } } - select { - case <-ctx.Done(): - errorf("ctx should not be canceled yet") - default: + if !testTimeout { + select { + case <-ctx.Done(): + errorf("ctx should not be canceled yet") + default: + } } if s, prefix := fmt.Sprint(ctx), "context.Background."; !strings.HasPrefix(s, prefix) { t.Errorf("ctx.String() = %q want prefix %q", s, prefix) @@ -608,7 +617,7 @@ func testLayers(t testingT, seed int64, testTimeout bool) { } checkValues("after timeout") } else { - cancel := cancels[rand.Intn(len(cancels))] + cancel := cancels[r.Intn(len(cancels))] cancel() select { case <-ctx.Done(): diff --git a/src/context/example_test.go b/src/context/example_test.go index b91a8acef3..72ac5d2e49 100644 --- a/src/context/example_test.go +++ b/src/context/example_test.go @@ -10,6 +10,8 @@ import ( "time" ) +const shortDuration = 1 * time.Millisecond // a reasonable duration to block in an example + // This example demonstrates the use of a cancelable context to prevent a // goroutine leak. By the end of the example function, the goroutine started // by gen will return without leaking. @@ -55,7 +57,7 @@ func ExampleWithCancel() { // This example passes a context with an arbitrary deadline to tell a blocking // function that it should abandon its work as soon as it gets to it. func ExampleWithDeadline() { - d := time.Now().Add(50 * time.Millisecond) + d := time.Now().Add(shortDuration) ctx, cancel := context.WithDeadline(context.Background(), d) // Even though ctx will be expired, it is good practice to call its @@ -79,7 +81,7 @@ func ExampleWithDeadline() { func ExampleWithTimeout() { // Pass a context with a timeout to tell a blocking function that it // should abandon its work after the timeout elapses. - ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond) + ctx, cancel := context.WithTimeout(context.Background(), shortDuration) defer cancel() select { |