github.com/adityamillind98/moby@v23.0.0-rc.4+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  	"os/signal"
     7  	"sync/atomic"
     8  	"syscall"
     9  )
    10  
    11  // Trap sets up a simplified signal "trap", appropriate for common
    12  // behavior expected from a vanilla unix command-line tool in general
    13  // (and the Docker engine in particular).
    14  //
    15  //   - If SIGINT or SIGTERM are received, `cleanup` is called, then the process is terminated.
    16  //   - If SIGINT or SIGTERM are received 3 times before cleanup is complete, then cleanup is
    17  //     skipped and the process is terminated immediately (allows force quit of stuck daemon)
    18  //   - Ignore SIGPIPE events. These are generated by systemd when journald is restarted while
    19  //     the docker daemon is not restarted and also running under systemd.
    20  //     Fixes https://github.com/docker/docker/issues/19728
    21  func Trap(cleanup func(), logger interface {
    22  	Info(args ...interface{})
    23  }) {
    24  	c := make(chan os.Signal, 1)
    25  	// we will handle INT, TERM, SIGPIPE here
    26  	signal.Notify(c, os.Interrupt, syscall.SIGTERM, syscall.SIGPIPE)
    27  	go func() {
    28  		interruptCount := uint32(0)
    29  		for sig := range c {
    30  			if sig == syscall.SIGPIPE {
    31  				continue
    32  			}
    33  
    34  			go func(sig os.Signal) {
    35  				logger.Info(fmt.Sprintf("Processing signal '%v'", sig))
    36  				switch sig {
    37  				case os.Interrupt, syscall.SIGTERM:
    38  					if atomic.LoadUint32(&interruptCount) < 3 {
    39  						// Initiate the cleanup only once
    40  						if atomic.AddUint32(&interruptCount, 1) == 1 {
    41  							// Call the provided cleanup handler
    42  							cleanup()
    43  							os.Exit(0)
    44  						} else {
    45  							return
    46  						}
    47  					} else {
    48  						// 3 SIGTERM/INT signals received; force exit without cleanup
    49  						logger.Info("Forcing docker daemon shutdown without cleanup; 3 interrupts received")
    50  					}
    51  				}
    52  				// for the SIGINT/TERM non-clean shutdown case, exit with 128 + signal #
    53  				os.Exit(128 + int(sig.(syscall.Signal)))
    54  			}(sig)
    55  		}
    56  	}()
    57  }