Add cache package.

pkg/client/cache/cache.go

@@ -0,0 +1,71 @@
+/*
+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 cache
+
+import (
+	"sync"
+)
+
+type cache struct {
+	lock  sync.RWMutex
+	items map[string]interface{}
+}
+
+// Add inserts an item into the cache.
+func (c *cache) Add(ID string, obj interface{}) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.items[ID] = obj
+}
+
+// Update sets an item in the cache to its updated state.
+func (c *cache) Update(ID string, obj interface{}) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.items[ID] = obj
+}
+
+// Delete removes an item from the cache.
+func (c *cache) Delete(ID string, obj interface{}) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	delete(c.items, ID)
+}
+
+// List returns a list of all the items.
+func (c *cache) List() []interface{} {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	list := make([]interface{}, 0, len(c.items))
+	for _, item := range c.items {
+		list = append(list, item)
+	}
+	return list
+}
+
+// Get returns the requested item, or sets exists=false.
+func (c *cache) Get(ID string) (item interface{}, exists bool) {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	item, exists = c.items[ID]
+	return item, exists
+}
+
+// NewStore returns a Store implemented simply with a map and a lock.
+func NewStore() Store {
+	return &cache{items: map[string]interface{}{}}
+}

pkg/client/cache/doc.go

@@ -0,0 +1,24 @@
+/*
+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 cache is a client-side caching mechanism. It is useful for
+// reducing the number of server calls you'd otherwise need to make.
+// Getter watches a server and updates a Store. Two stores are provided;
+// one that simply caches objects (for example, to allow a scheduler to
+// list currently available minions), and one that additionally acts as
+// a FIFO queue (for example, to allow a scheduler to process incoming
+// pods).
+package cache

pkg/client/cache/fifo.go

@@ -0,0 +1,107 @@
+/*
+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 cache
+
+import (
+	"sync"
+)
+
+type FIFO struct {
+	lock  sync.RWMutex
+	cond  sync.Cond
+	items map[string]interface{}
+	queue []string
+}
+
+// Add inserts an item, and puts it in the queue.
+func (f *FIFO) Add(ID string, obj interface{}) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	f.items[ID] = obj
+	f.queue = append(f.queue, ID)
+	f.cond.Broadcast()
+}
+
+// Update updates an item, and adds it to the queue.
+func (f *FIFO) Update(ID string, obj interface{}) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	f.items[ID] = obj
+	f.queue = append(f.queue, ID)
+	f.cond.Broadcast()
+}
+
+// Delete removes an item. It doesn't add it to the queue, because
+// this implementation assumes the consumer only cares about the objects,
+// not the order in which they were created/added.
+func (f *FIFO) Delete(ID string, obj interface{}) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	delete(f.items, ID)
+}
+
+// List returns a list of all the items.
+func (f *FIFO) List() []interface{} {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+	list := make([]interface{}, 0, len(f.items))
+	for _, item := range f.items {
+		list = append(list, item)
+	}
+	return list
+}
+
+// Get returns the requested item, or sets exists=false.
+func (f *FIFO) Get(ID string) (item interface{}, exists bool) {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+	item, exists = f.items[ID]
+	return item, exists
+}
+
+// Pop waits until an item is ready and returns it. If multiple items are
+// ready, they are returned in the order in which they were added/updated.
+// The item is removed from the queue (and the store) before it is returned,
+// so if you don't succesfully process it, you need to add it back with Add().
+func (f *FIFO) Pop() interface{} {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	for {
+		for len(f.queue) == 0 {
+			f.cond.Wait()
+		}
+		id := f.queue[0]
+		f.queue = f.queue[1:]
+		item, ok := f.items[id]
+		if !ok {
+			// Item may have been deleted subsequently.
+			continue
+		}
+		return item
+	}
+}
+
+// NewFIFOStore returns a Store which can be used to queue up items to
+// process.
+func NewFIFOStore() *FIFO {
+	f := &FIFO{
+		items: map[string]interface{}{},
+		queue: []string{},
+	}
+	f.cond.L = &f.lock
+	return f
+}

pkg/client/cache/getter.go

@@ -0,0 +1,104 @@
+/*
+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 cache
+
+import (
+	"reflect"
+	"time"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/watch"
+	"github.com/golang/glog"
+)
+
+// Store is a generic object storage interface. Getter knows how to watch a server
+// and update a store. A generic store is provided, which allows Getter to be used
+// as a local caching system, and an LRU store, which allows Getter to work like a
+// queue of items yet to be processed.
+type Store interface {
+	Add(ID string, obj interface{})
+	Update(ID string, obj interface{})
+	Delete(ID string, obj interface{})
+	List() []interface{}
+	Get(ID string) (item interface{}, exists bool)
+}
+
+// Getter watches a specified resource and causes all changes to be reflected in the given store.
+type Getter struct {
+	kubeClient   *client.Client
+	resource     string
+	expectedType reflect.Type
+	store        Store
+}
+
+// NewGetter makes a new Getter object which will keep the given store up to
+// date with the server's contents for the given resource. Getter promises to
+// only put things in the store that have the type of expectedType.
+// TODO: define a query so you only locally cache a subset of items.
+func NewGetter(resource string, kubeClient *client.Client, expectedType interface{}, store Store) *Getter {
+	gc := &Getter{
+		resource:     resource,
+		kubeClient:   kubeClient,
+		store:        store,
+		expectedType: reflect.TypeOf(expectedType),
+	}
+	return gc
+}
+
+func (gc *Getter) Run() {
+	go util.Forever(gc.watch, 5*time.Second)
+}
+
+func (gc *Getter) watch() {
+	w, err := gc.kubeClient.Get().Path(gc.resource).Watch()
+	if err != nil {
+		glog.Errorf("failed to watch %v: %v", gc.resource, err)
+		return
+	}
+	gc.watchHandler(w)
+}
+
+func (gc *Getter) watchHandler(w watch.Interface) {
+	for {
+		event, ok := <-w.ResultChan()
+		if !ok {
+			glog.Errorf("unexpected watch close")
+			return
+		}
+		if e, a := gc.expectedType, reflect.TypeOf(event.Object); e != a {
+			glog.Errorf("expected type %v, but watch event object had type %v", e, a)
+			continue
+		}
+		jsonBase, err := api.FindJSONBase(event.Object)
+		if err != nil {
+			glog.Errorf("unable to understand watch event %#v", event)
+			continue
+		}
+		switch event.Type {
+		case watch.Added:
+			gc.store.Add(jsonBase.ID(), event.Object)
+		case watch.Modified:
+			gc.store.Update(jsonBase.ID(), event.Object)
+		case watch.Deleted:
+			gc.store.Delete(jsonBase.ID(), event.Object)
+		default:
+			glog.Errorf("unable to understand watch event %#v", event)
+		}
+	}
+}

pkg/client/cache/store_test.go

@@ -0,0 +1,64 @@
+/*
+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 cache
+
+import (
+	"testing"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
+)
+
+// Test public interface
+func doTestStore(t *testing.T, store Store) {
+	store.Add("foo", "bar")
+	if item, ok := store.Get("foo"); !ok {
+		t.Errorf("didn't find inserted item")
+	} else {
+		if e, a := "bar", item.(string); e != a {
+			t.Errorf("expected %v, got %v", e, a)
+		}
+	}
+	store.Update("foo", "baz")
+	if item, ok := store.Get("foo"); !ok {
+		t.Errorf("didn't find inserted item")
+	} else {
+		if e, a := "baz", item.(string); e != a {
+			t.Errorf("expected %v, got %v", e, a)
+		}
+	}
+	store.Delete("foo", "qux")
+	if _, ok := store.Get("foo"); ok {
+		t.Errorf("found deleted item??")
+	}
+	store.Add("a", "b")
+	store.Add("c", "d")
+	store.Add("e", "e")
+	found := util.StringSet{}
+	for _, item := range store.List() {
+		found.Insert(item.(string))
+	}
+	if !found.HasAll("b", "d", "e") {
+		t.Errorf("missing items")
+	}
+	if len(found) != 3 {
+		t.Errorf("extra items")
+	}
+}
+
+func TestCache(t *testing.T) {
+	doTestStore(t, NewStore())
+}