tailscale/net/netmon/loghelper_test.go
Brad Fitzpatrick 8b48f3847d net/netmon, wgengine/magicsock: simplify LinkChangeLogLimiter signature
Remove the need for the caller to hold on to and call an unregister
function. Both two callers (one real, one test) already have a context
they can use. Use context.AfterFunc instead. There are no observable
side effects from scheduling too late if the goroutine doesn't run sync.

Updates #17148

Change-Id: Ie697dae0e797494fa8ef27fbafa193bfe5ceb307
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2025-09-15 16:12:24 -07:00

92 lines
2.2 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package netmon
import (
"bytes"
"context"
"fmt"
"testing"
"testing/synctest"
"tailscale.com/util/eventbus"
)
func TestLinkChangeLogLimiter(t *testing.T) { synctest.Test(t, syncTestLinkChangeLogLimiter) }
func syncTestLinkChangeLogLimiter(t *testing.T) {
bus := eventbus.New()
defer bus.Close()
mon, err := New(bus, t.Logf)
if err != nil {
t.Fatal(err)
}
defer mon.Close()
var logBuffer bytes.Buffer
logf := func(format string, args ...any) {
t.Logf("captured log: "+format, args...)
if format[len(format)-1] != '\n' {
format += "\n"
}
fmt.Fprintf(&logBuffer, format, args...)
}
ctx, cancel := context.WithCancel(t.Context())
defer cancel()
logf = LinkChangeLogLimiter(ctx, logf, mon)
// Log once, which should write to our log buffer.
logf("hello %s", "world")
if got := logBuffer.String(); got != "hello world\n" {
t.Errorf("unexpected log buffer contents: %q", got)
}
// Log again, which should not write to our log buffer.
logf("hello %s", "andrew")
if got := logBuffer.String(); got != "hello world\n" {
t.Errorf("unexpected log buffer contents: %q", got)
}
// Log a different message, which should write to our log buffer.
logf("other message")
if got := logBuffer.String(); got != "hello world\nother message\n" {
t.Errorf("unexpected log buffer contents: %q", got)
}
// Synthesize a fake major change event, which should clear the format
// string cache and allow the next log to write to our log buffer.
//
// InjectEvent doesn't work because it's not a major event, so we
// instead reach into the netmon and grab the callback, and then call
// it ourselves.
mon.mu.Lock()
var cb func(*ChangeDelta)
for _, c := range mon.cbs {
cb = c
break
}
mon.mu.Unlock()
cb(&ChangeDelta{Major: true})
logf("hello %s", "world")
if got := logBuffer.String(); got != "hello world\nother message\nhello world\n" {
t.Errorf("unexpected log buffer contents: %q", got)
}
// Canceling the context we passed to LinkChangeLogLimiter should
// unregister the callback from the netmon.
cancel()
synctest.Wait()
mon.mu.Lock()
if len(mon.cbs) != 0 {
t.Errorf("expected no callbacks, got %v", mon.cbs)
}
mon.mu.Unlock()
}