github.com/docker/engine@v22.0.0-20211208180946-d456264580cf+incompatible/cmd/dockerd/trap/trap.go (about)

     1  package trap // import "github.com/docker/docker/cmd/dockerd/trap"
     2  
     3  import (
     4  	"fmt"
     5  	"os"
     6  	gosignal "os/signal"
     7  	"sync/atomic"
     8  	"syscall"
     9  
    10  	"github.com/docker/docker/pkg/stack"
    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  // * Ignore SIGPIPE events. These are generated by systemd when journald is restarted while
    22  //   the docker daemon is not restarted and also running under systemd.
    23  //   Fixes https://github.com/docker/docker/issues/19728
    24  //
    25  func Trap(cleanup func(), logger interface {
    26  	Info(args ...interface{})
    27  }) {
    28  	c := make(chan os.Signal, 1)
    29  	// we will handle INT, TERM, QUIT, SIGPIPE here
    30  	signals := []os.Signal{os.Interrupt, syscall.SIGTERM, syscall.SIGQUIT, syscall.SIGPIPE}
    31  	gosignal.Notify(c, signals...)
    32  	go func() {
    33  		interruptCount := uint32(0)
    34  		for sig := range c {
    35  			if sig == syscall.SIGPIPE {
    36  				continue
    37  			}
    38  
    39  			go func(sig os.Signal) {
    40  				logger.Info(fmt.Sprintf("Processing signal '%v'", sig))
    41  				switch sig {
    42  				case os.Interrupt, syscall.SIGTERM:
    43  					if atomic.LoadUint32(&interruptCount) < 3 {
    44  						// Initiate the cleanup only once
    45  						if atomic.AddUint32(&interruptCount, 1) == 1 {
    46  							// Call the provided cleanup handler
    47  							cleanup()
    48  							os.Exit(0)
    49  						} else {
    50  							return
    51  						}
    52  					} else {
    53  						// 3 SIGTERM/INT signals received; force exit without cleanup
    54  						logger.Info("Forcing docker daemon shutdown without cleanup; 3 interrupts received")
    55  					}
    56  				case syscall.SIGQUIT:
    57  					stack.Dump()
    58  					logger.Info("Forcing docker daemon shutdown without cleanup on SIGQUIT")
    59  				}
    60  				// for the SIGINT/TERM, and SIGQUIT non-clean shutdown case, exit with 128 + signal #
    61  				os.Exit(128 + int(sig.(syscall.Signal)))
    62  			}(sig)
    63  		}
    64  	}()
    65  }