85 lines
2.3 KiB
Go
85 lines
2.3 KiB
Go
/*
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* Copyright (C) 2020-2022, IrineSistiana
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*
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* This file is part of mosdns.
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*
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* mosdns is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* mosdns is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package safe_close
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import "sync"
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// SafeClose can achieve safe close where WaitClosed returns only after
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// all sub goroutines exited.
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//
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// 1. Main service goroutine starts and wait on ReceiveCloseSignal.
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// 2. Any service's sub goroutine should be started by Attach and wait on ReceiveCloseSignal.
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// 3. If any fatal err occurs, any service goroutine can call SendCloseSignal to close the service.
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// 4. Any third party caller can call SendCloseSignal to close the service.
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type SafeClose struct {
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m sync.Mutex
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wg sync.WaitGroup
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closeSignal chan struct{}
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closeErr error
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}
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func NewSafeClose() *SafeClose {
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return &SafeClose{
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closeSignal: make(chan struct{}),
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}
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}
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// WaitClosed waits until all SendCloseSignal is called and all
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// attached funcs in SafeClose are done.
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func (s *SafeClose) WaitClosed() error {
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<-s.closeSignal
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s.wg.Wait()
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return s.closeErr
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}
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// SendCloseSignal sends a close signal. Unblock WaitClosed.
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// The given error will be read by WaitClosed.
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// Once SendCloseSignal is called, following calls are noop.
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func (s *SafeClose) SendCloseSignal(err error) {
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s.m.Lock()
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select {
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case <-s.closeSignal:
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default:
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s.closeErr = err
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close(s.closeSignal)
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}
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s.m.Unlock()
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}
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func (s *SafeClose) ReceiveCloseSignal() <-chan struct{} {
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return s.closeSignal
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}
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// Attach add this goroutine to s.wg WaitClosed.
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// f must receive closeSignal and call done when it is done.
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// If s was closed, f will not run.
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func (s *SafeClose) Attach(f func(done func(), closeSignal <-chan struct{})) {
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s.m.Lock()
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select {
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case <-s.closeSignal:
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default:
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s.wg.Add(1)
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go func() {
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f(s.wg.Done, s.closeSignal)
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}()
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}
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s.m.Unlock()
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}
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