mirror of
https://github.com/tailscale/tailscale.git
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114 lines
3.0 KiB
Go
114 lines
3.0 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 logger defines a type for writing to logs. It's just a
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// convenience type so that we don't have to pass verbose func(...)
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// types around.
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package logger
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import (
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"container/list"
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"fmt"
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"io"
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"log"
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"sync"
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"golang.org/x/time/rate"
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)
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// Logf is the basic Tailscale logger type: a printf-like func.
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// Like log.Printf, the format need not end in a newline.
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// Logf functions must be safe for concurrent use.
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type Logf func(format string, args ...interface{})
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// WithPrefix wraps f, prefixing each format with the provided prefix.
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func WithPrefix(f Logf, prefix string) Logf {
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return func(format string, args ...interface{}) {
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f(prefix+format, args...)
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}
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}
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// FuncWriter returns an io.Writer that writes to f.
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func FuncWriter(f Logf) io.Writer {
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return funcWriter{f}
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}
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// StdLogger returns a standard library logger from a Logf.
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func StdLogger(f Logf) *log.Logger {
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return log.New(FuncWriter(f), "", 0)
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}
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type funcWriter struct{ f Logf }
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func (w funcWriter) Write(p []byte) (int, error) {
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w.f("%s", p)
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return len(p), nil
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}
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// Discard is a Logf that throws away the logs given to it.
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func Discard(string, ...interface{}) {}
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// limitData is used to keep track of each format string's associated
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// rate-limiting data.
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type limitData struct {
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lim *rate.Limiter // the token bucket associated with this string
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msgBlocked bool // whether a "duplicate error" message has already been logged
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ele *list.Element // list element used to access this string in the cache
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}
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// RateLimitedFn returns a rate-limiting Logf wrapping the given logf.
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// Messages are allowed through at a maximum of f messages/second, in
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// bursts of up to burst messages at a time. Up to maxCache strings will be held at a time.
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func RateLimitedFn(logf Logf, f float64, burst int, maxCache int) Logf {
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r := rate.Limit(f)
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var (
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mu sync.Mutex
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msgLim = make(map[string]*limitData) // keyed by logf format
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msgCache = list.New() // a rudimentary LRU that limits the size of the map
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)
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type verdict int
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const (
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allow verdict = iota
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warn
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block
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)
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judge := func(format string) verdict {
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mu.Lock()
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defer mu.Unlock()
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rl, ok := msgLim[format]
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if ok {
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msgCache.MoveToFront(rl.ele)
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} else {
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rl = &limitData{lim: rate.NewLimiter(r, burst), ele: msgCache.PushFront(format)}
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msgLim[format] = rl
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if msgCache.Len() > maxCache {
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delete(msgLim, msgCache.Back().Value.(string))
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msgCache.Remove(msgCache.Back())
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}
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}
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if rl.lim.Allow() {
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rl.msgBlocked = false
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return allow
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}
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if !rl.msgBlocked {
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rl.msgBlocked = true
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return warn
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}
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return block
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}
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return func(format string, args ...interface{}) {
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switch judge(format) {
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case allow:
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logf(format, args...)
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case warn:
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logf("Repeated messages were suppressed by rate limiting. Original message: %s",
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fmt.Sprintf(format, args...))
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}
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}
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}
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