diff --git a/build/log_shutdown.go b/build/log_shutdown.go new file mode 100644 index 000000000..d83ff99ec --- /dev/null +++ b/build/log_shutdown.go @@ -0,0 +1,53 @@ +package build + +import ( + "github.com/btcsuite/btclog" + "github.com/lightningnetwork/lnd/signal" +) + +// ShutdownLogger wraps an existing logger with a shutdown function which will +// be called on Critical/Criticalf to prompt shutdown. +type ShutdownLogger struct { + btclog.Logger +} + +// NewShutdownLogger creates a shutdown logger for the log provided which will +// use the signal package to request shutdown on critical errors. +func NewShutdownLogger(logger btclog.Logger) *ShutdownLogger { + return &ShutdownLogger{ + Logger: logger, + } +} + +// Criticalf formats message according to format specifier and writes to +// log with LevelCritical. It will then call the shutdown logger's shutdown +// function to prompt safe shutdown. +// +// Note: it is part of the btclog.Logger interface. +func (s *ShutdownLogger) Criticalf(format string, params ...interface{}) { + s.Logger.Criticalf(format, params...) + s.shutdown() +} + +// Critical formats message using the default formats for its operands +// and writes to log with LevelCritical. It will then call the shutdown +// logger's shutdown function to prompt safe shutdown. +// +// Note: it is part of the btclog.Logger interface. +func (s *ShutdownLogger) Critical(v ...interface{}) { + s.Logger.Critical(v) + s.shutdown() +} + +// shutdown checks whether we are listening for interrupts, since a shutdown +// request to the signal package will block if it is not running, and requests +// shutdown if possible. +func (s *ShutdownLogger) shutdown() { + if !signal.Listening() { + s.Logger.Info("Request for shutdown ignored") + return + } + + s.Logger.Info("Sending request for shutdown") + signal.RequestShutdown() +} diff --git a/build/logrotator.go b/build/logrotator.go index 734a3bd7e..2474d2d8c 100644 --- a/build/logrotator.go +++ b/build/logrotator.go @@ -39,7 +39,10 @@ func NewRotatingLogWriter() *RotatingLogWriter { logWriter := &LogWriter{} backendLog := btclog.NewBackend(logWriter) return &RotatingLogWriter{ - GenSubLogger: backendLog.Logger, + GenSubLogger: func(tag string) btclog.Logger { + logger := backendLog.Logger(tag) + return NewShutdownLogger(logger) + }, logWriter: logWriter, backendLog: backendLog, subsystemLoggers: SubLoggers{}, diff --git a/cmd/lncli/cmd_open_channel.go b/cmd/lncli/cmd_open_channel.go index b7e78d132..412306ba2 100644 --- a/cmd/lncli/cmd_open_channel.go +++ b/cmd/lncli/cmd_open_channel.go @@ -414,7 +414,10 @@ func openChannelPsbt(ctx *cli.Context, client lnrpc.LightningClient, if err != nil { return fmt.Errorf("opening stream to server failed: %v", err) } - signal.Intercept() + + if err := signal.Intercept(); err != nil { + return err + } // We also need to spawn a goroutine that reads from the server. This // will copy the messages to the channel as long as they come in or add diff --git a/cmd/lnd/main.go b/cmd/lnd/main.go index 9364afbe2..8fb99ed02 100644 --- a/cmd/lnd/main.go +++ b/cmd/lnd/main.go @@ -19,7 +19,10 @@ func main() { } // Hook interceptor for os signals. - signal.Intercept() + if err := signal.Intercept(); err != nil { + _, _ = fmt.Fprintln(os.Stderr, err) + os.Exit(1) + } // Call the "real" main in a nested manner so the defers will properly // be executed in the case of a graceful shutdown. diff --git a/mobile/bindings.go b/mobile/bindings.go index fcf8c11df..aff3c8199 100644 --- a/mobile/bindings.go +++ b/mobile/bindings.go @@ -54,7 +54,10 @@ func Start(extraArgs string, unlockerReady, rpcReady Callback) { } // Hook interceptor for os signals. - signal.Intercept() + if err := signal.Intercept(); err != nil { + _, _ = fmt.Fprintln(os.Stderr, err) + os.Exit(1) + } // Set up channels that will be notified when the RPC servers are ready // to accept calls. diff --git a/signal/signal.go b/signal/signal.go index 82e503d03..927931fdd 100644 --- a/signal/signal.go +++ b/signal/signal.go @@ -6,8 +6,10 @@ package signal import ( + "errors" "os" "os/signal" + "sync/atomic" "syscall" ) @@ -19,6 +21,10 @@ var ( // gracefully, similar to when receiving SIGINT. shutdownRequestChannel = make(chan struct{}) + // started indicates whether we have started our main interrupt handler. + // This field should be used atomically. + started int32 + // quit is closed when instructing the main interrupt handler to exit. quit = make(chan struct{}) @@ -26,8 +32,13 @@ var ( shutdownChannel = make(chan struct{}) ) -// Intercept starts the interception of interrupt signals. -func Intercept() { +// Intercept starts the interception of interrupt signals. Note that this +// function can only be called once. +func Intercept() error { + if !atomic.CompareAndSwapInt32(&started, 0, 1) { + return errors.New("intercept already started") + } + signalsToCatch := []os.Signal{ os.Interrupt, os.Kill, @@ -37,6 +48,8 @@ func Intercept() { } signal.Notify(interruptChannel, signalsToCatch...) go mainInterruptHandler() + + return nil } // mainInterruptHandler listens for SIGINT (Ctrl+C) signals on the @@ -85,6 +98,20 @@ func mainInterruptHandler() { } } +// Listening returns true if the main interrupt handler has been started, and +// has not been killed. +func Listening() bool { + // If our started field is not set, we are not yet listening for + // interrupts. + if atomic.LoadInt32(&started) != 1 { + return false + } + + // If we have started our main goroutine, we check whether we have + // stopped it yet. + return Alive() +} + // Alive returns true if the main interrupt handler has not been killed. func Alive() bool { select {