79 lines
2.5 KiB
Go
79 lines
2.5 KiB
Go
/*
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Copyright 2021 The cert-manager Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package util
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import (
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"os"
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"os/signal"
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"syscall"
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)
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var onlyOneSignalHandler = make(chan struct{})
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var errorExitCodeChannel = make(chan int, 1)
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// ExitBehavior controls how the program should be terminated
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// in response to a shutdown signal.
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type ExitBehavior int
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const (
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// AlwaysErrCode indicates the exit code of the program should always be nonzero
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// and should correspond to the numeric value of the signal that was received.
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AlwaysErrCode ExitBehavior = iota
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// GracefulShutdown treats a shutdown signal as a request to exit gracefully, terminating
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// goroutines and returning an exit code of 0 if there are no errors during shutdown.
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GracefulShutdown ExitBehavior = iota
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)
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// SetupExitHandler:
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// A stop channel is returned which is closed on receiving a shutdown signal (SIGTERM
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// or SIGINT). If a second signal is caught, the program is terminated directly with
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// exit code 130.
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// SetupExitHandler also returns an exit function, this exit function calls os.Exit(...)
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// if there is a exit code in the errorExitCodeChannel.
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// The errorExitCodeChannel receives exit codes when SetExitCode is called or when
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// a shutdown signal is received (only if exitBehavior is AlwaysErrCode).
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func SetupExitHandler(exitBehavior ExitBehavior) (<-chan struct{}, func()) {
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close(onlyOneSignalHandler) // panics when called twice
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stop := make(chan struct{})
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c := make(chan os.Signal, 2)
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signal.Notify(c, shutdownSignals...)
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go func() {
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// first signal. Close stop chan and pass exit code to exitCodeChannel.
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exitCode := 128 + int((<-c).(syscall.Signal))
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if exitBehavior == AlwaysErrCode {
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errorExitCodeChannel <- exitCode
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}
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close(stop)
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// second signal. Exit directly.
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<-c
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os.Exit(130)
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}()
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return stop, func() {
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select {
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case signal := <-errorExitCodeChannel:
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os.Exit(signal)
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default:
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// Do not exit, there are no exit codes in the channel,
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// so just continue and let the main function go out of
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// scope instead.
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}
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}
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}
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