net: add more timing slop for TestDialParallel on Windows

Fixes #35616

Change-Id: I51b2490100cfe0e902da09eee8d027e0ec86ed53
Reviewed-on: https://go-review.googlesource.com/c/go/+/207466
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/net/dial_test.go b/src/net/dial_test.go
index 4312a6df7143a2d2ef45cf18e3eae7937d57c3ca..ae40079f853a580056c628daf7532354cdb7145a 100644 (file)
--- a/src/net/dial_test.go
+++ b/src/net/dial_test.go
@@ -155,7 +155,7 @@ func slowDialTCP(ctx context.Context, network string, laddr, raddr *TCPAddr) (*T
        return c, err
 }
 
-func dialClosedPort() (actual, expected time.Duration) {
+func dialClosedPort(t *testing.T) (actual, expected time.Duration) {
        // Estimate the expected time for this platform.
        // On Windows, dialing a closed port takes roughly 1 second,
        // but other platforms should be instantaneous.
@@ -169,6 +169,7 @@ func dialClosedPort() (actual, expected time.Duration) {
 
        l, err := Listen("tcp", "127.0.0.1:0")
        if err != nil {
+               t.Logf("dialClosedPort: Listen failed: %v", err)
                return 999 * time.Hour, expected
        }
        addr := l.Addr().String()
@@ -184,6 +185,7 @@ func dialClosedPort() (actual, expected time.Duration) {
                }
                elapsed := time.Now().Sub(startTime)
                if i == 2 {
+                       t.Logf("dialClosedPort: measured delay %v", elapsed)
                        return elapsed, expected
                }
        }
@@ -196,7 +198,7 @@ func TestDialParallel(t *testing.T) {
                t.Skip("both IPv4 and IPv6 are required")
        }
 
-       closedPortDelay, expectClosedPortDelay := dialClosedPort()
+       closedPortDelay, expectClosedPortDelay := dialClosedPort(t)
        if closedPortDelay > expectClosedPortDelay {
                t.Errorf("got %v; want <= %v", closedPortDelay, expectClosedPortDelay)
        }
@@ -317,8 +319,14 @@ func TestDialParallel(t *testing.T) {
                        t.Errorf("#%d: got nil; want non-nil", i)
                }
 
-               expectElapsedMin := tt.expectElapsed - 95*time.Millisecond
-               expectElapsedMax := tt.expectElapsed + 95*time.Millisecond
+               // We used to always use 95 milliseconds as the slop,
+               // but that was flaky on Windows.  See issue 35616.
+               slop := 95 * time.Millisecond
+               if fifth := tt.expectElapsed / 5; fifth > slop {
+                       slop = fifth
+               }
+               expectElapsedMin := tt.expectElapsed - slop
+               expectElapsedMax := tt.expectElapsed + slop
                if elapsed < expectElapsedMin {
                        t.Errorf("#%d: got %v; want >= %v", i, elapsed, expectElapsedMin)
                } else if elapsed > expectElapsedMax {
@@ -667,7 +675,7 @@ func TestDialerDualStack(t *testing.T) {
                t.Skip("both IPv4 and IPv6 are required")
        }
 
-       closedPortDelay, expectClosedPortDelay := dialClosedPort()
+       closedPortDelay, expectClosedPortDelay := dialClosedPort(t)
        if closedPortDelay > expectClosedPortDelay {
                t.Errorf("got %v; want <= %v", closedPortDelay, expectClosedPortDelay)
        }