172 lines
3.8 KiB
Go
172 lines
3.8 KiB
Go
/*
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Copyright 2015 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 workqueue
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import (
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"sync"
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)
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type Interface interface {
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Add(item interface{})
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Len() int
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Get() (item interface{}, shutdown bool)
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Done(item interface{})
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ShutDown()
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ShuttingDown() bool
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}
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// New constructs a new workqueue (see the package comment).
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func New() *Type {
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return NewNamed("")
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}
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func NewNamed(name string) *Type {
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return &Type{
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dirty: set{},
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processing: set{},
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cond: sync.NewCond(&sync.Mutex{}),
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metrics: newQueueMetrics(name),
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}
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}
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// Type is a work queue (see the package comment).
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type Type struct {
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// queue defines the order in which we will work on items. Every
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// element of queue should be in the dirty set and not in the
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// processing set.
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queue []t
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// dirty defines all of the items that need to be processed.
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dirty set
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// Things that are currently being processed are in the processing set.
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// These things may be simultaneously in the dirty set. When we finish
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// processing something and remove it from this set, we'll check if
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// it's in the dirty set, and if so, add it to the queue.
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processing set
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cond *sync.Cond
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shuttingDown bool
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metrics queueMetrics
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}
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type empty struct{}
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type t interface{}
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type set map[t]empty
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func (s set) has(item t) bool {
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_, exists := s[item]
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return exists
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}
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func (s set) insert(item t) {
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s[item] = empty{}
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}
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func (s set) delete(item t) {
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delete(s, item)
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}
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// Add marks item as needing processing.
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func (q *Type) Add(item interface{}) {
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q.cond.L.Lock()
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defer q.cond.L.Unlock()
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if q.shuttingDown {
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return
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}
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if q.dirty.has(item) {
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return
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}
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q.metrics.add(item)
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q.dirty.insert(item)
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if q.processing.has(item) {
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return
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}
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q.queue = append(q.queue, item)
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q.cond.Signal()
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}
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// Len returns the current queue length, for informational purposes only. You
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// shouldn't e.g. gate a call to Add() or Get() on Len() being a particular
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// value, that can't be synchronized properly.
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func (q *Type) Len() int {
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q.cond.L.Lock()
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defer q.cond.L.Unlock()
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return len(q.queue)
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}
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// Get blocks until it can return an item to be processed. If shutdown = true,
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// the caller should end their goroutine. You must call Done with item when you
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// have finished processing it.
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func (q *Type) Get() (item interface{}, shutdown bool) {
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q.cond.L.Lock()
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defer q.cond.L.Unlock()
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for len(q.queue) == 0 && !q.shuttingDown {
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q.cond.Wait()
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}
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if len(q.queue) == 0 {
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// We must be shutting down.
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return nil, true
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}
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item, q.queue = q.queue[0], q.queue[1:]
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q.metrics.get(item)
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q.processing.insert(item)
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q.dirty.delete(item)
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return item, false
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}
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// Done marks item as done processing, and if it has been marked as dirty again
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// while it was being processed, it will be re-added to the queue for
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// re-processing.
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func (q *Type) Done(item interface{}) {
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q.cond.L.Lock()
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defer q.cond.L.Unlock()
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q.metrics.done(item)
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q.processing.delete(item)
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if q.dirty.has(item) {
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q.queue = append(q.queue, item)
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q.cond.Signal()
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}
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}
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// ShutDown will cause q to ignore all new items added to it. As soon as the
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// worker goroutines have drained the existing items in the queue, they will be
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// instructed to exit.
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func (q *Type) ShutDown() {
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q.cond.L.Lock()
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defer q.cond.L.Unlock()
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q.shuttingDown = true
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q.cond.Broadcast()
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}
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func (q *Type) ShuttingDown() bool {
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q.cond.L.Lock()
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defer q.cond.L.Unlock()
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return q.shuttingDown
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}
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