1184a4d8d1
This commit prevents a race that could happen on shutdown if a sigint was received between adding the first the interrupt handler and and future handlers. This code is loosely based on initial pull request #154 which was not accepted due to introducing a race of its own. Thanks to @tuxcanfly for the intial pull request and finding the issue.
82 lines
2.3 KiB
Go
82 lines
2.3 KiB
Go
// Copyright (c) 2013-2014 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package main
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import (
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"os"
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"os/signal"
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)
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// interruptChannel is used to receive SIGINT (Ctrl+C) signals.
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var interruptChannel chan os.Signal
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// addHandlerChannel is used to add an interrupt handler to the list of handlers
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// to be invoked on SIGINT (Ctrl+C) signals.
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var addHandlerChannel = make(chan func())
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// mainInterruptHandler listens for SIGINT (Ctrl+C) signals on the
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// interruptChannel and invokes the registered interruptCallbacks accordingly.
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// It also listens for callback registration. It must be run as a goroutine.
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func mainInterruptHandler() {
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// interruptCallbacks is a list of callbacks to invoke when a
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// SIGINT (Ctrl+C) is received.
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var interruptCallbacks []func()
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// isShutdown is a flag which is used to indicate whether or not
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// the shutdown signal has already been received and hence any future
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// attempts to add a new interrupt handler should invoke them
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// immediately.
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var isShutdown bool
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for {
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select {
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case <-interruptChannel:
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// Ignore more than one shutdown signal.
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if isShutdown {
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btcdLog.Infof("Received SIGINT (Ctrl+C). " +
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"Already shutting down...")
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continue
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}
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isShutdown = true
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btcdLog.Infof("Received SIGINT (Ctrl+C). Shutting down...")
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// Run handlers in LIFO order.
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for i := range interruptCallbacks {
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idx := len(interruptCallbacks) - 1 - i
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callback := interruptCallbacks[idx]
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callback()
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}
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// Signal the main goroutine to shutdown.
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go func() {
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shutdownChannel <- struct{}{}
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}()
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case handler := <-addHandlerChannel:
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// The shutdown signal has already been received, so
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// just invoke and new handlers immediately.
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if isShutdown {
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handler()
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}
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interruptCallbacks = append(interruptCallbacks, handler)
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}
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}
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}
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// addInterruptHandler adds a handler to call when a SIGINT (Ctrl+C) is
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// received.
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func addInterruptHandler(handler func()) {
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// Create the channel and start the main interrupt handler which invokes
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// all other callbacks and exits if not already done.
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if interruptChannel == nil {
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interruptChannel = make(chan os.Signal, 1)
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signal.Notify(interruptChannel, os.Interrupt)
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go mainInterruptHandler()
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}
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addHandlerChannel <- handler
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}
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