lnd.xprv/signal.go

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// Copyright (c) 2013-2017 The btcsuite developers
// Copyright (c) 2015-2016 The Decred developers
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// Heavily inspired by https://github.com/btcsuite/btcd/blob/master/signal.go
// Copyright (C) 2015-2017 The Lightning Network Developers
package main
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import (
"os"
"os/signal"
)
// interruptChannel is used to receive SIGINT (Ctrl+C) signals.
var interruptChannel chan os.Signal
// shutdownRequestChannel is used to request the daemon to shutdown gracefully,
// similar to when receiving SIGINT.
var shutdownRequestChannel = make(chan struct{})
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// addHandlerChannel is used to add an interrupt handler to the list of handlers
// to be invoked on SIGINT (Ctrl+C) signals and shutdown.
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var addHandlerChannel = make(chan func())
// mainInterruptHandler listens for SIGINT (Ctrl+C) signals on the
// interruptChannel and shutdown requests on the shutdownRequestChannel, and
// invokes the registered interruptCallbacks accordingly. It also listens for
// callback registration.
// It must be run as a goroutine.
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func mainInterruptHandler() {
// interruptCallbacks is a list of callbacks to invoke when a
// SIGINT (Ctrl+C) or a shutdown request is received.
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var interruptCallbacks []func()
// isShutdown is a flag which is used to indicate whether or not
// the shutdown signal has already been received and hence any future
// attempts to add a new interrupt handler should invoke them
// immediately.
var isShutdown bool
// shutdown invokes the registered interrupt handlers, then signals the
// shutdownChannel.
shutdown := func() {
// Ignore more than one shutdown signal.
if isShutdown {
ltndLog.Infof("Already shutting down...")
return
}
isShutdown = true
ltndLog.Infof("Shutting down...")
// Run handlers in LIFO order.
for i := range interruptCallbacks {
idx := len(interruptCallbacks) - 1 - i
callback := interruptCallbacks[idx]
callback()
}
// Signal the main goroutine to shutdown.
go func() {
shutdownChannel <- struct{}{}
}()
}
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for {
select {
case <-interruptChannel:
ltndLog.Infof("Received SIGINT (Ctrl+C).")
shutdown()
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case <-shutdownRequestChannel:
ltndLog.Infof("Received shutdown request.")
shutdown()
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case handler := <-addHandlerChannel:
// The shutdown signal has already been received, so
// just invoke any new handlers immediately.
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if isShutdown {
handler()
}
interruptCallbacks = append(interruptCallbacks, handler)
}
}
}
// addInterruptHandler adds a handler to call when a SIGINT (Ctrl+C) or a
// shutdown request is received.
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func addInterruptHandler(handler func()) {
// Create the channel and start the main interrupt handler which invokes
// all other callbacks and exits if not already done.
if interruptChannel == nil {
interruptChannel = make(chan os.Signal, 1)
signal.Notify(interruptChannel, os.Interrupt)
go mainInterruptHandler()
}
addHandlerChannel <- handler
}