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08acb502e5
If a test calls log.Printf, 'go test' horrifyingly rearranges the output to no longer be in chronological order, which makes debugging virtually impossible. Let's stop that from happening by making log.Printf panic if called from any module, no matter how deep, during tests. This required us to change the default error handler in at least one http.Server, as well as plumbing a bunch of logf functions around, especially in magicsock and wgengine, but also in logtail and backoff. To add insult to injury, 'go test' also rearranges the output when a parent test has multiple sub-tests (all the sub-test's t.Logf is always printed after all the parent tests t.Logf), so we need to screw around with a special Logf that can point at the "current" t (current_t.Logf) in some places. Probably our entire way of using subtests is wrong, since 'go test' would probably like to run them all in parallel if you called t.Parallel(), but it definitely can't because the're all manipulating the shared state created by the parent test. They should probably all be separate toplevel tests instead, with common setup/teardown logic. But that's a job for another time. Signed-off-by: Avery Pennarun <apenwarr@tailscale.com>
66 lines
1.6 KiB
Go
66 lines
1.6 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 backoff
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import (
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"context"
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"math/rand"
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"time"
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"tailscale.com/types/logger"
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)
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const MAX_BACKOFF_MSEC = 30000
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type Backoff struct {
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n int
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// Name is the name of this backoff timer, for logging purposes.
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name string
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// logf is the function used for log messages when backing off.
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logf logger.Logf
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// NewTimer is the function that acts like time.NewTimer().
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// You can override this in unit tests.
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NewTimer func(d time.Duration) *time.Timer
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// LogLongerThan sets the minimum time of a single backoff interval
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// before we mention it in the log.
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LogLongerThan time.Duration
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}
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func NewBackoff(name string, logf logger.Logf) Backoff {
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return Backoff{
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name: name,
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logf: logf,
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NewTimer: time.NewTimer,
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}
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}
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func (b *Backoff) BackOff(ctx context.Context, err error) {
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if ctx.Err() == nil && err != nil {
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b.n++
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// n^2 backoff timer is a little smoother than the
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// common choice of 2^n.
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msec := b.n * b.n * 10
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if msec > MAX_BACKOFF_MSEC {
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msec = MAX_BACKOFF_MSEC
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}
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// Randomize the delay between 0.5-1.5 x msec, in order
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// to prevent accidental "thundering herd" problems.
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msec = rand.Intn(msec) + msec/2
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dur := time.Duration(msec) * time.Millisecond
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if dur >= b.LogLongerThan {
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b.logf("%s: backoff: %d msec\n", b.name, msec)
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}
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t := b.NewTimer(dur)
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select {
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case <-ctx.Done():
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t.Stop()
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case <-t.C:
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}
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} else {
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// not a regular error
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b.n = 0
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}
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}
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