package trap // import "github.com/docker/docker/cmd/dockerd/trap" import ( "fmt" "os" gosignal "os/signal" "sync/atomic" "syscall" "github.com/docker/docker/pkg/stack" ) // Trap sets up a simplified signal "trap", appropriate for common // behavior expected from a vanilla unix command-line tool in general // (and the Docker engine in particular). // // - If SIGINT or SIGTERM are received, `cleanup` is called, then the process is terminated. // - If SIGINT or SIGTERM are received 3 times before cleanup is complete, then cleanup is // skipped and the process is terminated immediately (allows force quit of stuck daemon) // - A SIGQUIT always causes an exit without cleanup, with a goroutine dump preceding exit. // - Ignore SIGPIPE events. These are generated by systemd when journald is restarted while // the docker daemon is not restarted and also running under systemd. // Fixes https://github.com/docker/docker/issues/19728 func Trap(cleanup func(), logger interface { Info(args ...interface{}) }) { c := make(chan os.Signal, 1) // we will handle INT, TERM, QUIT, SIGPIPE here signals := []os.Signal{os.Interrupt, syscall.SIGTERM, syscall.SIGQUIT, syscall.SIGPIPE} gosignal.Notify(c, signals...) go func() { interruptCount := uint32(0) for sig := range c { if sig == syscall.SIGPIPE { continue } go func(sig os.Signal) { logger.Info(fmt.Sprintf("Processing signal '%v'", sig)) switch sig { case os.Interrupt, syscall.SIGTERM: if atomic.LoadUint32(&interruptCount) < 3 { // Initiate the cleanup only once if atomic.AddUint32(&interruptCount, 1) == 1 { // Call the provided cleanup handler cleanup() os.Exit(0) } else { return } } else { // 3 SIGTERM/INT signals received; force exit without cleanup logger.Info("Forcing docker daemon shutdown without cleanup; 3 interrupts received") } case syscall.SIGQUIT: stack.Dump() logger.Info("Forcing docker daemon shutdown without cleanup on SIGQUIT") } // for the SIGINT/TERM, and SIGQUIT non-clean shutdown case, exit with 128 + signal # os.Exit(128 + int(sig.(syscall.Signal))) }(sig) } }() }