package signal import ( "os" gosignal "os/signal" "runtime" "sync/atomic" "syscall" "github.com/Sirupsen/logrus" ) // 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. // func Trap(cleanup func()) { c := make(chan os.Signal, 1) // we will handle INT, TERM, QUIT here signals := []os.Signal{os.Interrupt, syscall.SIGTERM, syscall.SIGQUIT} gosignal.Notify(c, signals...) go func() { interruptCount := uint32(0) for sig := range c { go func(sig os.Signal) { logrus.Infof("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 logrus.Infof("Forcing docker daemon shutdown without cleanup; 3 interrupts received") } case syscall.SIGQUIT: DumpStacks() logrus.Infof("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) } }() } // DumpStacks dumps the runtime stack. func DumpStacks() { buf := make([]byte, 16384) buf = buf[:runtime.Stack(buf, true)] // Note that if the daemon is started with a less-verbose log-level than "info" (the default), the goroutine // traces won't show up in the log. logrus.Infof("=== BEGIN goroutine stack dump ===\n%s\n=== END goroutine stack dump ===", buf) }