signal/signal: creates package for monitoring of OS signals
This commit is contained in:
Conner Fromknecht
parent
8ab464b4d1
commit
0ae6dec4f3
96
signal.go
96
signal.go
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// Copyright (c) 2013-2017 The btcsuite developers
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// Copyright (c) 2015-2016 The Decred developers
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// Heavily inspired by https://github.com/btcsuite/btcd/blob/master/signal.go
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// Copyright (C) 2015-2017 The Lightning Network Developers
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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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// shutdownRequestChannel is used to request the daemon to shutdown gracefully,
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// similar to when receiving SIGINT.
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var shutdownRequestChannel = make(chan struct{})
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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 and shutdown.
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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 shutdown requests on the shutdownRequestChannel, and
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// invokes the registered interruptCallbacks accordingly. It also listens for
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// callback registration.
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// 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) or a shutdown request 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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// shutdown invokes the registered interrupt handlers, then signals the
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// shutdownChannel.
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shutdown := func() {
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// Ignore more than one shutdown signal.
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if isShutdown {
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ltndLog.Infof("Already shutting down...")
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return
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}
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isShutdown = true
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ltndLog.Infof("Shutting down...")
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// Execute the interrupt callbacks in FIFO order.
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for _, callback := range interruptCallbacks {
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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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}
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for {
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select {
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case <-interruptChannel:
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ltndLog.Infof("Received SIGINT (Ctrl+C).")
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shutdown()
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case <-shutdownRequestChannel:
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ltndLog.Infof("Received shutdown request.")
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shutdown()
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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 any 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) or a
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// shutdown request is 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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101
signal/signal.go
Normal file
101
signal/signal.go
Normal file
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@ -0,0 +1,101 @@
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// Copyright (c) 2013-2017 The btcsuite developers
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// Copyright (c) 2015-2016 The Decred developers
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// Heavily inspired by https://github.com/btcsuite/btcd/blob/master/signal.go
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// Copyright (C) 2015-2017 The Lightning Network Developers
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package signal
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import (
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"os"
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"os/signal"
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)
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var (
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// interruptChannel is used to receive SIGINT (Ctrl+C) signals.
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interruptChannel = make(chan os.Signal, 1)
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// shutdownRequestChannel is used to request the daemon to shutdown
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// gracefully, similar to when receiving SIGINT.
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shutdownRequestChannel = make(chan struct{})
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// quit is closed when instructing the main interrupt handler to exit.
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quit = make(chan struct{})
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// shutdownChannel is closed once the main interrupt handler exits.
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shutdownChannel = make(chan struct{})
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)
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func init() {
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signal.Notify(interruptChannel, os.Interrupt)
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go mainInterruptHandler()
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}
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// mainInterruptHandler listens for SIGINT (Ctrl+C) signals on the
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// interruptChannel and shutdown requests on the shutdownRequestChannel, and
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// invokes the registered interruptCallbacks accordingly. It also listens for
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// callback registration.
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// It must be run as a goroutine.
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func mainInterruptHandler() {
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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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// shutdown invokes the registered interrupt handlers, then signals the
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// shutdownChannel.
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shutdown := func() {
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// Ignore more than one shutdown signal.
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if isShutdown {
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log.Infof("Already shutting down...")
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return
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}
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isShutdown = true
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log.Infof("Shutting down...")
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// Signal the main interrupt handler to exit, and stop accept
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// post-facto requests.
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close(quit)
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}
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for {
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select {
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case <-interruptChannel:
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log.Infof("Received SIGINT (Ctrl+C).")
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shutdown()
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case <-shutdownRequestChannel:
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log.Infof("Received shutdown request.")
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shutdown()
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case <-quit:
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log.Infof("Gracefully shutting down.")
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close(shutdownChannel)
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return
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}
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}
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}
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// Alive returns true if the main interrupt handler has not been killed.
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func Alive() bool {
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select {
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case <-quit:
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return false
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default:
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return true
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}
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}
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// RequestShutdown initiates a graceful shutdown from the application.
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func RequestShutdown() {
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select {
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case shutdownRequestChannel <- struct{}{}:
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case <-quit:
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}
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}
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// ShutdownChannel returns the channel that will be closed once the main
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// interrupt handler has exited.
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func ShutdownChannel() <-chan struct{} {
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return shutdownChannel
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}
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