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moby--moby/pkg/signal/trap.go

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package signal
import (
"os"
gosignal "os/signal"
"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 repeated 3 times before cleanup is complete, then cleanup is
// skipped and the process terminated directly.
// * If "DEBUG" is set in the environment, SIGQUIT causes an exit without cleanup.
//
func Trap(cleanup func()) {
c := make(chan os.Signal, 1)
signals := []os.Signal{os.Interrupt, syscall.SIGTERM}
if os.Getenv("DEBUG") == "" {
signals = append(signals, syscall.SIGQUIT)
}
gosignal.Notify(c, signals...)
go func() {
interruptCount := uint32(0)
for sig := range c {
go func(sig os.Signal) {
logrus.Infof("Received signal '%v', starting shutdown of docker...", sig)
switch sig {
case os.Interrupt, syscall.SIGTERM:
// If the user really wants to interrupt, let him do so.
if atomic.LoadUint32(&interruptCount) < 3 {
// Initiate the cleanup only once
if atomic.AddUint32(&interruptCount, 1) == 1 {
// Call cleanup handler
cleanup()
os.Exit(0)
} else {
return
}
} else {
logrus.Infof("Force shutdown of docker, interrupting cleanup")
}
case syscall.SIGQUIT:
}
os.Exit(128 + int(sig.(syscall.Signal)))
}(sig)
}
}()
}