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

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package signal
import (
"os"
gosignal "os/signal"
"runtime"
"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 received 3 times before cleanup is complete, then cleanup is
// skipped and the process is terminated immediately (allows force quit of stuck daemon)
// * A SIGQUIT always causes an exit without cleanup, with a goroutine dump preceding exit.
//
func Trap(cleanup func()) {
c := make(chan os.Signal, 1)
// we will handle INT, TERM, QUIT here
signals := []os.Signal{os.Interrupt, syscall.SIGTERM, syscall.SIGQUIT}
gosignal.Notify(c, signals...)
go func() {
interruptCount := uint32(0)
for sig := range c {
go func(sig os.Signal) {
logrus.Infof("Processing signal '%v'", sig)
switch sig {
case os.Interrupt, syscall.SIGTERM:
if atomic.LoadUint32(&interruptCount) < 3 {
// Initiate the cleanup only once
if atomic.AddUint32(&interruptCount, 1) == 1 {
// Call the provided cleanup handler
cleanup()
os.Exit(0)
} else {
return
}
} else {
// 3 SIGTERM/INT signals received; force exit without cleanup
logrus.Infof("Forcing docker daemon shutdown without cleanup; 3 interrupts received")
}
case syscall.SIGQUIT:
DumpStacks()
logrus.Infof("Forcing docker daemon shutdown without cleanup on SIGQUIT")
}
//for the SIGINT/TERM, and SIGQUIT non-clean shutdown case, exit with 128 + signal #
os.Exit(128 + int(sig.(syscall.Signal)))
}(sig)
}
}()
}
// DumpStacks dumps the runtime stack.
func DumpStacks() {
var (
buf []byte
stackSize int
)
bufferLen := 16384
for stackSize == len(buf) {
buf = make([]byte, bufferLen)
stackSize = runtime.Stack(buf, true)
bufferLen *= 2
}
buf = buf[:stackSize]
// Note that if the daemon is started with a less-verbose log-level than "info" (the default), the goroutine
// traces won't show up in the log.
logrus.Infof("=== BEGIN goroutine stack dump ===\n%s\n=== END goroutine stack dump ===", buf)
}