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a19c110dd3
Fixes #3921 Change-Id: I8186053b5c09c43f0358b4e7fdd131361a6d8f2e Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
145 lines
3.8 KiB
Go
145 lines
3.8 KiB
Go
// Copyright (c) 2022 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 envknob provides access to environment-variable tweakable
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// debug settings.
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//
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// These are primarily knobs used by Tailscale developers during
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// development or by users when instructed to by Tailscale developers
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// when debugging something. They are not a stable interface and may
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// be removed or any time.
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//
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// A related package, control/controlknobs, are knobs that can be
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// changed at runtime by the control plane. Sometimes both are used:
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// an envknob for the default/explicit value, else falling back
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// to the controlknob value.
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package envknob
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import (
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"log"
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"os"
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"strconv"
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"sync"
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"tailscale.com/types/opt"
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)
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var (
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mu sync.Mutex
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set = map[string]string{}
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list []string
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)
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func noteEnv(k, v string) {
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if v == "" {
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return
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}
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mu.Lock()
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defer mu.Unlock()
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if _, ok := set[v]; !ok {
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list = append(list, k)
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}
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set[k] = v
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}
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// logf is logger.Logf, but logger depends on envknob, so for circular
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// dependency reasons, make a type alias (so it's still assignable,
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// but has nice docs here).
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type logf = func(format string, args ...interface{})
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// LogCurrent logs the currently set environment knobs.
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func LogCurrent(logf logf) {
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mu.Lock()
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defer mu.Unlock()
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for _, k := range list {
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logf("envknob: %s=%q", k, set[k])
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}
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}
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// String returns the named environment variable, using os.Getenv.
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//
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// If the variable is non-empty, it's also tracked & logged as being
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// an in-use knob.
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func String(envVar string) string {
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v := os.Getenv(envVar)
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noteEnv(envVar, v)
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return v
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}
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// Bool returns the boolean value of the named environment variable.
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// If the variable is not set, it returns false.
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// An invalid value exits the binary with a failure.
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func Bool(envVar string) bool {
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return boolOr(envVar, false)
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}
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// BoolDefaultTrue is like Bool, but returns true by default if the
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// environment variable isn't present.
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func BoolDefaultTrue(envVar string) bool {
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return boolOr(envVar, true)
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}
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func boolOr(envVar string, implicitValue bool) bool {
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val := os.Getenv(envVar)
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if val == "" {
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return implicitValue
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}
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b, err := strconv.ParseBool(val)
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if err == nil {
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noteEnv(envVar, strconv.FormatBool(b)) // canonicalize
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return b
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}
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log.Fatalf("invalid boolean environment variable %s value %q", envVar, val)
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panic("unreachable")
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}
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// LookupBool returns the boolean value of the named environment value.
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// The ok result is whether a value was set.
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// If the value isn't a valid int, it exits the program with a failure.
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func LookupBool(envVar string) (v bool, ok bool) {
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val := os.Getenv(envVar)
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if val == "" {
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return false, false
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}
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b, err := strconv.ParseBool(val)
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if err == nil {
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return b, true
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}
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log.Fatalf("invalid boolean environment variable %s value %q", envVar, val)
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panic("unreachable")
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}
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// OptBool is like Bool, but returns an opt.Bool, so the caller can
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// distinguish between implicitly and explicitly false.
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func OptBool(envVar string) opt.Bool {
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b, ok := LookupBool(envVar)
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if !ok {
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return ""
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}
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var ret opt.Bool
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ret.Set(b)
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return ret
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}
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// LookupInt returns the integer value of the named environment value.
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// The ok result is whether a value was set.
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// If the value isn't a valid int, it exits the program with a failure.
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func LookupInt(envVar string) (v int, ok bool) {
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val := os.Getenv(envVar)
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if val == "" {
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return 0, false
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}
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v, err := strconv.Atoi(val)
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if err == nil {
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noteEnv(envVar, val)
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return v, true
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}
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log.Fatalf("invalid integer environment variable %s: %v", envVar, val)
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panic("unreachable")
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}
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// UseWIPCode is whether TAILSCALE_USE_WIP_CODE is set to permit use
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// of Work-In-Progress code.
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func UseWIPCode() bool { return Bool("TAILSCALE_USE_WIP_CODE") }
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