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tailscale/envknob/logknob/logknob.go

85 lines
2.4 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package logknob provides a helpful wrapper that allows enabling logging
// based on either an envknob or other methods of enablement.
package logknob
import (
"sync/atomic"
"golang.org/x/exp/slices"
"tailscale.com/envknob"
"tailscale.com/types/logger"
)
// TODO(andrew-d): should we have a package-global registry of logknobs? It
// would allow us to update from a netmap in a central location, which might be
// reason enough to do it...
// LogKnob allows configuring verbose logging, with multiple ways to enable. It
// supports enabling logging via envknob, via atomic boolean (for use in e.g.
// c2n log level changes), and via capabilities from a NetMap (so users can
// enable logging via the ACL JSON).
type LogKnob struct {
capName string
cap atomic.Bool
env func() bool
manual atomic.Bool
}
// NewLogKnob creates a new LogKnob, with the provided environment variable
// name and/or NetMap capability.
func NewLogKnob(env, cap string) *LogKnob {
if env == "" && cap == "" {
panic("must provide either an environment variable or capability")
}
lk := &LogKnob{
capName: cap,
}
if env != "" {
lk.env = envknob.RegisterBool(env)
} else {
lk.env = func() bool { return false }
}
return lk
}
// Set will cause logs to be printed when called with Set(true). When called
// with Set(false), logs will not be printed due to an earlier call of
// Set(true), but may be printed due to either the envknob and/or capability of
// this LogKnob.
func (lk *LogKnob) Set(v bool) {
lk.manual.Store(v)
}
// NetMap is an interface for the parts of netmap.NetworkMap that we care
// about; we use this rather than a concrete type to avoid a circular
// dependency.
type NetMap interface {
SelfCapabilities() []string
}
// UpdateFromNetMap will enable logging if the SelfNode in the provided NetMap
// contains the capability provided for this LogKnob.
func (lk *LogKnob) UpdateFromNetMap(nm NetMap) {
if lk.capName == "" {
return
}
lk.cap.Store(slices.Contains(nm.SelfCapabilities(), lk.capName))
}
// Do will call log with the provided format and arguments if any of the
// configured methods for enabling logging are true.
func (lk *LogKnob) Do(log logger.Logf, format string, args ...any) {
if lk.shouldLog() {
log(format, args...)
}
}
func (lk *LogKnob) shouldLog() bool {
return lk.manual.Load() || lk.env() || lk.cap.Load()
}