blob: e5f332c80cfae9fd560d6e2a024290cb319a2f36 [file] [log] [blame]
// Copyright 2017 The Upspin Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package shutdown provides a mechanism for registering handlers to be called
// on process shutdown.
package shutdown // import ""
import (
// GracePeriod specifies the maximum amount of time during which all shutdown
// handlers must complete before the process forcibly exits.
const GracePeriod = 1 * time.Minute
// Handle registers the onShutdown function to be run when the system is being
// shut down. On shutdown, registered functions are run in last-in-first-out
// order. Handle may be called concurrently.
func Handle(onShutdown func()) {
shutdown.sequence = append(shutdown.sequence, onShutdown)
// Now calls all registered shutdown closures in last-in-first-out order and
// terminates the process with the given status code.
// It only executes once and guarantees termination within GracePeriod.
// Now may be called concurrently.
func Now(code int) {
shutdown.once.Do(func() {
log.Debug.Printf("shutdown: status code %d", code)
// Ensure we terminate after a fixed amount of time.
go func() {
// Don't use log package here; it may have been flushed already.
fmt.Fprintf(os.Stderr, "shutdown: %v elapsed since shutdown requested; exiting forcefully", GracePeriod)
}() // No need to ever unlock.
for i := len(shutdown.sequence) - 1; i >= 0; i-- {
// Testing hook.
var killSleep = time.Sleep
var shutdown struct {
mu sync.Mutex
sequence []func()
once sync.Once
func init() {
// Close the listener when a shutdown event happens.
c := make(chan os.Signal, 1)
signal.Notify(c, syscall.SIGTERM, os.Interrupt)
go func() {
sig := <-c
log.Error.Printf("shutdown: process received signal %v", sig)
// Register the log shutdown routine here, to avoid an import cycle.
// Shutting down the logger is the last thing we do.