add work queue; test coverage 100%

pkg/util/workqueue/doc.go

+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+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 workqueue provides a simple queue that supports the following
+// features:
+//  * Fair: items processed in the order in which they are added.
+//  * Stingy: a single item will not be processed multiple times concurrently,
+//      and if an item is added multiple times before it can be processed, it
+//      will only be processed once.
+//  * Multiple consumers and producers. In particular, it is allowed for an
+//      item to be reenqueued while it is being processed.
+//  * Shutdown notifications.
+package workqueue

pkg/util/workqueue/queue.go

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

pkg/util/workqueue/queue_test.go

+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+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 workqueue_test
+
+import (
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util/workqueue"
+)
+
+func TestBasic(t *testing.T) {
+	// If something is seriously wrong this test will never complete.
+	q := workqueue.New()
+
+	// Start producers
+	const producers = 50
+	producerWG := sync.WaitGroup{}
+	producerWG.Add(producers)
+	for i := 0; i < producers; i++ {
+		go func(i int) {
+			defer producerWG.Done()
+			for j := 0; j < 50; j++ {
+				q.Add(i)
+				time.Sleep(time.Millisecond)
+			}
+		}(i)
+	}
+
+	// Start consumers
+	const consumers = 10
+	consumerWG := sync.WaitGroup{}
+	consumerWG.Add(consumers)
+	for i := 0; i < consumers; i++ {
+		go func(i int) {
+			defer consumerWG.Done()
+			for {
+				item, quit := q.Get()
+				if item == "added after shutdown!" {
+					t.Errorf("Got an item added after shutdown.")
+				}
+				if quit {
+					return
+				}
+				t.Logf("Worker %v: begin processing %v", i, item)
+				time.Sleep(3 * time.Millisecond)
+				t.Logf("Worker %v: done processing %v", i, item)
+				q.Done(item)
+			}
+		}(i)
+	}
+
+	producerWG.Wait()
+	q.ShutDown()
+	q.Add("added after shutdown!")
+	consumerWG.Wait()
+}
+
+func TestAddWhileProcessing(t *testing.T) {
+	q := workqueue.New()
+
+	// Start producers
+	const producers = 50
+	producerWG := sync.WaitGroup{}
+	producerWG.Add(producers)
+	for i := 0; i < producers; i++ {
+		go func(i int) {
+			defer producerWG.Done()
+			q.Add(i)
+		}(i)
+	}
+
+	// Start consumers
+	const consumers = 10
+	consumerWG := sync.WaitGroup{}
+	consumerWG.Add(consumers)
+	for i := 0; i < consumers; i++ {
+		go func(i int) {
+			defer consumerWG.Done()
+			// Every worker will re-add every item up to two times.
+			// This tests the dirty-while-processing case.
+			counters := map[interface{}]int{}
+			for {
+				item, quit := q.Get()
+				if quit {
+					return
+				}
+				counters[item]++
+				if counters[item] < 2 {
+					q.Add(item)
+				}
+				q.Done(item)
+			}
+		}(i)
+	}
+
+	producerWG.Wait()
+	q.ShutDown()
+	consumerWG.Wait()
+}