A new package can also later record/report which knobs are checked and set. It also makes the code cleaner & easier to grep for env knobs. Change-Id: Id8a123ab7539f1fadbd27e0cbeac79c2e4f09751 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>main
Brad Fitzpatrick
4 years ago
committed by
Brad Fitzpatrick
parent
6feb8f4c51
commit
41fd4eab5c
@ -0,0 +1,102 @@ |
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// 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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"tailscale.com/types/opt" |
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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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// In the future it will also track usage for reporting on debug pages.
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func String(envVar string) string { |
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return os.Getenv(envVar) |
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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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return b |
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} |
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log.Fatalf("invalid environment variable %s value %q: %v", envVar, val, err) |
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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 environment variable %s value %q: %v", envVar, val, err) |
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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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return v, true |
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} |
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log.Fatalf("invalid environment variable %s value %q: %v", envVar, val, err) |
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panic("unreachable") |
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} |
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