First commit

core/sigtrap.go

@@ -0,0 +1,71 @@
+package core
+
+import (
+	"log"
+	"os"
+	"os/signal"
+	"sync"
+
+	"github.com/miekg/coredns/server"
+)
+
+// TrapSignals create signal handlers for all applicable signals for this
+// system. If your Go program uses signals, this is a rather invasive
+// function; best to implement them yourself in that case. Signals are not
+// required for the caddy package to function properly, but this is a
+// convenient way to allow the user to control this package of your program.
+func TrapSignals() {
+	trapSignalsCrossPlatform()
+	trapSignalsPosix()
+}
+
+// trapSignalsCrossPlatform captures SIGINT, which triggers forceful
+// shutdown that executes shutdown callbacks first. A second interrupt
+// signal will exit the process immediately.
+func trapSignalsCrossPlatform() {
+	go func() {
+		shutdown := make(chan os.Signal, 1)
+		signal.Notify(shutdown, os.Interrupt)
+
+		for i := 0; true; i++ {
+			<-shutdown
+
+			if i > 0 {
+				log.Println("[INFO] SIGINT: Force quit")
+				if PidFile != "" {
+					os.Remove(PidFile)
+				}
+				os.Exit(1)
+			}
+
+			log.Println("[INFO] SIGINT: Shutting down")
+
+			if PidFile != "" {
+				os.Remove(PidFile)
+			}
+
+			go os.Exit(executeShutdownCallbacks("SIGINT"))
+		}
+	}()
+}
+
+// executeShutdownCallbacks executes the shutdown callbacks as initiated
+// by signame. It logs any errors and returns the recommended exit status.
+// This function is idempotent; subsequent invocations always return 0.
+func executeShutdownCallbacks(signame string) (exitCode int) {
+	shutdownCallbacksOnce.Do(func() {
+		serversMu.Lock()
+		errs := server.ShutdownCallbacks(servers)
+		serversMu.Unlock()
+
+		if len(errs) > 0 {
+			for _, err := range errs {
+				log.Printf("[ERROR] %s shutdown: %v", signame, err)
+			}
+			exitCode = 1
+		}
+	})
+	return
+}
+
+var shutdownCallbacksOnce sync.Once