github.com/slava-ustovytski/docker@v1.8.2-rc1/pkg/signal/trap.go (about)

     1  package signal
     2  
     3  import (
     4  	"os"
     5  	gosignal "os/signal"
     6  	"runtime"
     7  	"sync/atomic"
     8  	"syscall"
     9  
    10  	"github.com/Sirupsen/logrus"
    11  )
    12  
    13  // Trap sets up a simplified signal "trap", appropriate for common
    14  // behavior expected from a vanilla unix command-line tool in general
    15  // (and the Docker engine in particular).
    16  //
    17  // * If SIGINT or SIGTERM are received, `cleanup` is called, then the process is terminated.
    18  // * If SIGINT or SIGTERM are received 3 times before cleanup is complete, then cleanup is
    19  //   skipped and the process is terminated immediately (allows force quit of stuck daemon)
    20  // * A SIGQUIT always causes an exit without cleanup, with a goroutine dump preceding exit.
    21  //
    22  func Trap(cleanup func()) {
    23  	c := make(chan os.Signal, 1)
    24  	// we will handle INT, TERM, QUIT here
    25  	signals := []os.Signal{os.Interrupt, syscall.SIGTERM, syscall.SIGQUIT}
    26  	gosignal.Notify(c, signals...)
    27  	go func() {
    28  		interruptCount := uint32(0)
    29  		for sig := range c {
    30  			go func(sig os.Signal) {
    31  				logrus.Infof("Processing signal '%v'", sig)
    32  				switch sig {
    33  				case os.Interrupt, syscall.SIGTERM:
    34  					if atomic.LoadUint32(&interruptCount) < 3 {
    35  						// Initiate the cleanup only once
    36  						if atomic.AddUint32(&interruptCount, 1) == 1 {
    37  							// Call the provided cleanup handler
    38  							cleanup()
    39  							os.Exit(0)
    40  						} else {
    41  							return
    42  						}
    43  					} else {
    44  						// 3 SIGTERM/INT signals received; force exit without cleanup
    45  						logrus.Infof("Forcing docker daemon shutdown without cleanup; 3 interrupts received")
    46  					}
    47  				case syscall.SIGQUIT:
    48  					DumpStacks()
    49  					logrus.Infof("Forcing docker daemon shutdown without cleanup on SIGQUIT")
    50  				}
    51  				//for the SIGINT/TERM, and SIGQUIT non-clean shutdown case, exit with 128 + signal #
    52  				os.Exit(128 + int(sig.(syscall.Signal)))
    53  			}(sig)
    54  		}
    55  	}()
    56  }
    57  
    58  func DumpStacks() {
    59  	buf := make([]byte, 16384)
    60  	buf = buf[:runtime.Stack(buf, true)]
    61  	// Note that if the daemon is started with a less-verbose log-level than "info" (the default), the goroutine
    62  	// traces won't show up in the log.
    63  	logrus.Infof("=== BEGIN goroutine stack dump ===\n%s\n=== END goroutine stack dump ===", buf)
    64  }