TUN-528: Move cloudflared into a separate repo

vendor/github.com/mholt/caddy/sigtrap.go

@@ -0,0 +1,108 @@
+// Copyright 2015 Light Code Labs, LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddy
+
+import (
+	"log"
+	"os"
+	"os/signal"
+	"sync"
+
+	"github.com/mholt/caddy/telemetry"
+)
+
+// 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 part 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")
+				for _, f := range OnProcessExit {
+					f() // important cleanup actions only
+				}
+				os.Exit(2)
+			}
+
+			log.Println("[INFO] SIGINT: Shutting down")
+
+			telemetry.AppendUnique("sigtrap", "SIGINT")
+			go telemetry.StopEmitting() // not guaranteed to finish in time; that's OK (just don't block!)
+
+			// important cleanup actions before shutdown callbacks
+			for _, f := range OnProcessExit {
+				f()
+			}
+
+			go func() {
+				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() {
+		// execute third-party shutdown hooks
+		EmitEvent(ShutdownEvent, signame)
+
+		errs := allShutdownCallbacks()
+		if len(errs) > 0 {
+			for _, err := range errs {
+				log.Printf("[ERROR] %s shutdown: %v", signame, err)
+			}
+			exitCode = 4
+		}
+	})
+	return
+}
+
+// allShutdownCallbacks executes all the shutdown callbacks
+// for all the instances, and returns all the errors generated
+// during their execution. An error executing one shutdown
+// callback does not stop execution of others. Only one shutdown
+// callback is executed at a time.
+func allShutdownCallbacks() []error {
+	var errs []error
+	instancesMu.Lock()
+	for _, inst := range instances {
+		errs = append(errs, inst.ShutdownCallbacks()...)
+	}
+	instancesMu.Unlock()
+	return errs
+}
+
+// shutdownCallbacksOnce ensures that shutdown callbacks
+// for all instances are only executed once.
+var shutdownCallbacksOnce sync.Once