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105 lines
3.2 KiB
Go
105 lines
3.2 KiB
Go
/*
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Copyright 2016 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package interrupt
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import (
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"os"
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"os/signal"
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"sync"
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"syscall"
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)
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// terminationSignals are signals that cause the program to exit in the
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// supported platforms (linux, darwin, windows).
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var terminationSignals = []os.Signal{syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT}
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// Handler guarantees execution of notifications after a critical section (the function passed
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// to a Run method), even in the presence of process termination. It guarantees exactly once
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// invocation of the provided notify functions.
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type Handler struct {
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notify []func()
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final func(os.Signal)
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once sync.Once
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}
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// Chain creates a new handler that invokes all notify functions when the critical section exits
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// and then invokes the optional handler's notifications. This allows critical sections to be
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// nested without losing exactly once invocations. Notify functions can invoke any cleanup needed
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// but should not exit (which is the responsibility of the parent handler).
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func Chain(handler *Handler, notify ...func()) *Handler {
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if handler == nil {
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return New(nil, notify...)
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}
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return New(handler.Signal, append(notify, handler.Close)...)
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}
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// New creates a new handler that guarantees all notify functions are run after the critical
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// section exits (or is interrupted by the OS), then invokes the final handler. If no final
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// handler is specified, the default final is `os.Exit(1)`. A handler can only be used for
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// one critical section.
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func New(final func(os.Signal), notify ...func()) *Handler {
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return &Handler{
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final: final,
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notify: notify,
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}
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}
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// Close executes all the notification handlers if they have not yet been executed.
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func (h *Handler) Close() {
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h.once.Do(func() {
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for _, fn := range h.notify {
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fn()
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}
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})
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}
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// Signal is called when an os.Signal is received, and guarantees that all notifications
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// are executed, then the final handler is executed. This function should only be called once
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// per Handler instance.
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func (h *Handler) Signal(s os.Signal) {
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h.once.Do(func() {
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for _, fn := range h.notify {
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fn()
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}
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if h.final == nil {
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os.Exit(1)
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}
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h.final(s)
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})
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}
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// Run ensures that any notifications are invoked after the provided fn exits (even if the
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// process is interrupted by an OS termination signal). Notifications are only invoked once
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// per Handler instance, so calling Run more than once will not behave as the user expects.
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func (h *Handler) Run(fn func() error) error {
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ch := make(chan os.Signal, 1)
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signal.Notify(ch, terminationSignals...)
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defer func() {
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signal.Stop(ch)
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close(ch)
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}()
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go func() {
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sig, ok := <-ch
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if !ok {
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return
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}
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h.Signal(sig)
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}()
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defer h.Close()
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return fn()
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}
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