test/channelz: Don't try to dial non-dialable addresses

On some platforms, dialing 127.0.0.1:0 doesn't fail immediately but
rather blocks until it times out. This leads to test failures because
the leak detector identifies stray goroutines.

In this case, there's no need to actually dial and rely on OS-specific
behavior. It's easier to err out directly.

Signed-off-by: Tom Wieczorek <[email protected]>

Author: twz123

test/channelz_test.go

@@ -21,6 +21,7 @@ package test
 import (
 	"context"
 	"crypto/tls"
+	"errors"
 	"fmt"
 	"net"
 	"regexp"
@@ -319,6 +320,11 @@ func (s) TestCZNestedChannelRegistrationAndDeletion(t *testing.T) {
 	e := tcpClearRREnv
 	// avoid calling API to set balancer type, which will void service config's change of balancer.
 	e.balancer = ""
+	e.customDialer = func(network, addr string, timeout time.Duration) (net.Conn, error) {
+		// Short-circuit the intentional 127.0.0.1:0 placeholder to avoid
+		// leakcheck flakes on platforms where dialing :0 blocks until timeout.
+		return nil, errors.New("intentionally failing to dial")
+	}
 	te := newTest(t, e)
 	r := manual.NewBuilderWithScheme("whatever")
 	te.resolverScheme = r.Scheme()
@@ -1500,6 +1506,11 @@ func (s) TestCZChannelTraceCreationDeletion(t *testing.T) {
 	e := tcpClearRREnv
 	// avoid calling API to set balancer type, which will void service config's change of balancer.
 	e.balancer = ""
+	e.customDialer = func(network, addr string, timeout time.Duration) (net.Conn, error) {
+		// Short-circuit the intentional 127.0.0.1:0 placeholder to avoid
+		// leakcheck flakes on platforms where dialing :0 blocks until timeout.
+		return nil, errors.New("intentionally failing to dial")
+	}
 	te := newTest(t, e)
 	r := manual.NewBuilderWithScheme("whatever")
 	te.resolverScheme = r.Scheme()
@@ -2008,6 +2019,11 @@ func (s) TestCZChannelConnectivityState(t *testing.T) {
 func (s) TestCZTraceOverwriteChannelDeletion(t *testing.T) {
 	e := tcpClearRREnv
 	e.balancer = ""
+	e.customDialer = func(network, addr string, timeout time.Duration) (net.Conn, error) {
+		// Short-circuit the intentional 127.0.0.1:0 placeholder to avoid
+		// leakcheck flakes on platforms where dialing :0 blocks until timeout.
+		return nil, errors.New("intentionally failing to dial")
+	}
 	te := newTest(t, e)
 	channelz.SetMaxTraceEntry(1)
 	defer channelz.ResetMaxTraceEntryToDefault()