github.com/Heebron/moby@v0.0.0-20221111184709-6eab4f55faf7/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  func Trap(cleanup func(), logger interface {
    25  	Info(args ...interface{})
    26  }) {
    27  	c := make(chan os.Signal, 1)
    28  	// we will handle INT, TERM, QUIT, SIGPIPE here
    29  	signals := []os.Signal{os.Interrupt, syscall.SIGTERM, syscall.SIGQUIT, syscall.SIGPIPE}
    30  	gosignal.Notify(c, signals...)
    31  	go func() {
    32  		interruptCount := uint32(0)
    33  		for sig := range c {
    34  			if sig == syscall.SIGPIPE {
    35  				continue
    36  			}
    37  
    38  			go func(sig os.Signal) {
    39  				logger.Info(fmt.Sprintf("Processing signal '%v'", sig))
    40  				switch sig {
    41  				case os.Interrupt, syscall.SIGTERM:
    42  					if atomic.LoadUint32(&interruptCount) < 3 {
    43  						// Initiate the cleanup only once
    44  						if atomic.AddUint32(&interruptCount, 1) == 1 {
    45  							// Call the provided cleanup handler
    46  							cleanup()
    47  							os.Exit(0)
    48  						} else {
    49  							return
    50  						}
    51  					} else {
    52  						// 3 SIGTERM/INT signals received; force exit without cleanup
    53  						logger.Info("Forcing docker daemon shutdown without cleanup; 3 interrupts received")
    54  					}
    55  				case syscall.SIGQUIT:
    56  					stack.Dump()
    57  					logger.Info("Forcing docker daemon shutdown without cleanup on SIGQUIT")
    58  				}
    59  				// for the SIGINT/TERM, and SIGQUIT non-clean shutdown case, exit with 128 + signal #
    60  				os.Exit(128 + int(sig.(syscall.Signal)))
    61  			}(sig)
    62  		}
    63  	}()
    64  }