kubelet: Add container reference manager.

Move the reference managing logic into container reference manager.
This enables pluggable container runtime to manage the container references.

pkg/kubelet/container_reference_manager.go

@@ -0,0 +1,87 @@
+/*
+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 kubelet
+
+import (
+	"sync"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+)
+
+// ContainerRefManager manages the references for the containers.
+// The references are used for reporting events such as creation,
+// failure, etc. This manager is thread-safe, no locks are necessary
+// for the caller.
+type ContainerRefManager struct {
+	sync.RWMutex
+	// TODO(yifan): To use strong type.
+	containerIDToRef map[string]*api.ObjectReference
+}
+
+// newContainerRefManager creates and returns a container reference manager
+// with empty contents.
+func newContainerRefManager() *ContainerRefManager {
+	c := ContainerRefManager{}
+	c.containerIDToRef = make(map[string]*api.ObjectReference)
+	return &c
+}
+
+// SetRef stores a reference to a pod's container, associating it with the given container id.
+func (c *ContainerRefManager) SetRef(id string, ref *api.ObjectReference) {
+	c.Lock()
+	defer c.Unlock()
+	c.containerIDToRef[id] = ref
+}
+
+// ClearRef forgets the given container id and its associated container reference.
+// TODO(yifan): This is currently never called. Consider to remove this function,
+// or figure out when to clear the references.
+func (c *ContainerRefManager) ClearRef(id string) {
+	c.Lock()
+	defer c.Unlock()
+	delete(c.containerIDToRef, id)
+}
+
+// GetRef returns the container reference of the given id, or (nil, false) if none is stored.
+func (c *ContainerRefManager) GetRef(id string) (ref *api.ObjectReference, ok bool) {
+	c.RLock()
+	defer c.RUnlock()
+	ref, ok = c.containerIDToRef[id]
+	return ref, ok
+}
+
+// GenerateContainerRef returns an *api.ObjectReference which references the given container within the
+// given pod. Returns an error if the reference can't be constructed or the container doesn't
+// actually belong to the pod.
+// TODO: Pods that came to us by static config or over HTTP have no selfLink set, which makes
+// this fail and log an error. Figure out how we want to identify these pods to the rest of the
+// system.
+// TODO(yifan): Revisit this function later, for current case, it does not need to use ContainerRefManager
+// as a receiver, and does not need to be exported.
+func (c *ContainerRefManager) GenerateContainerRef(pod *api.Pod, container *api.Container) (*api.ObjectReference, error) {
+	fieldPath, err := fieldPath(pod, container)
+	if err != nil {
+		// TODO: figure out intelligent way to refer to containers that we implicitly
+		// start (like the pod infra container). This is not a good way, ugh.
+		fieldPath = "implicitly required container " + container.Name
+	}
+	ref, err := api.GetPartialReference(pod, fieldPath)
+	if err != nil {
+		return nil, err
+	}
+	return ref, nil
+}

pkg/kubelet/kubelet.go

@@ -218,7 +218,7 @@ func NewMainKubelet(
 		rootDirectory:                  rootDirectory,
 		resyncInterval:                 resyncInterval,
 		podInfraContainerImage:         podInfraContainerImage,
-		containerIDToRef:               map[string]*api.ObjectReference{},
+		containerRefManager:            newContainerRefManager(),
 		runner:                         dockertools.NewDockerContainerCommandRunner(dockerClient),
 		httpClient:                     &http.Client{},
 		pullQPS:                        pullQPS,
@@ -296,8 +296,7 @@ type Kubelet struct {
 
 	// Needed to report events for containers belonging to deleted/modified pods.
 	// Tracks references for reporting events
-	containerIDToRef map[string]*api.ObjectReference
+	containerRefManager *ContainerRefManager
-	refLock          sync.RWMutex
 
 	// Optional, defaults to simple Docker implementation
 	dockerPuller dockertools.DockerPuller
@@ -685,54 +684,9 @@ func fieldPath(pod *api.Pod, container *api.Container) (string, error) {
 	return "", fmt.Errorf("container %#v not found in pod %#v", container, pod)
 }
 
-// containerRef returns an *api.ObjectReference which references the given container within the
-// given pod. Returns an error if the reference can't be constructed or the container doesn't
-// actually belong to the pod.
-// TODO: Pods that came to us by static config or over HTTP have no selfLink set, which makes
-// this fail and log an error. Figure out how we want to identify these pods to the rest of the
-// system.
-func containerRef(pod *api.Pod, container *api.Container) (*api.ObjectReference, error) {
-	fieldPath, err := fieldPath(pod, container)
-	if err != nil {
-		// TODO: figure out intelligent way to refer to containers that we implicitly
-		// start (like the pod infra container). This is not a good way, ugh.
-		fieldPath = "implicitly required container " + container.Name
-	}
-	ref, err := api.GetPartialReference(pod, fieldPath)
-	if err != nil {
-		return nil, err
-	}
-	return ref, nil
-}
-
-// setRef stores a reference to a pod's container, associating it with the given docker id.
-func (kl *Kubelet) setRef(id string, ref *api.ObjectReference) {
-	kl.refLock.Lock()
-	defer kl.refLock.Unlock()
-	if kl.containerIDToRef == nil {
-		kl.containerIDToRef = map[string]*api.ObjectReference{}
-	}
-	kl.containerIDToRef[id] = ref
-}
-
-// clearRef forgets the given docker id and its associated container reference.
-func (kl *Kubelet) clearRef(id string) {
-	kl.refLock.Lock()
-	defer kl.refLock.Unlock()
-	delete(kl.containerIDToRef, id)
-}
-
-// getRef returns the container reference of the given id, or (nil, false) if none is stored.
-func (kl *Kubelet) getRef(id string) (ref *api.ObjectReference, ok bool) {
-	kl.refLock.RLock()
-	defer kl.refLock.RUnlock()
-	ref, ok = kl.containerIDToRef[id]
-	return ref, ok
-}
-
 // Run a single container from a pod. Returns the docker container ID
 func (kl *Kubelet) runContainer(pod *api.Pod, container *api.Container, podVolumes volumeMap, netMode, ipcMode string) (id dockertools.DockerID, err error) {
-	ref, err := containerRef(pod, container)
+	ref, err := kl.containerRefManager.GenerateContainerRef(pod, container)
 	if err != nil {
 		glog.Errorf("Couldn't make a ref to pod %v, container %v: '%v'", pod.Name, container.Name, err)
 	}
@@ -773,7 +727,7 @@ func (kl *Kubelet) runContainer(pod *api.Pod, container *api.Container, podVolum
 	}
 	// Remember this reference so we can report events about this container
 	if ref != nil {
-		kl.setRef(dockerContainer.ID, ref)
+		kl.containerRefManager.SetRef(dockerContainer.ID, ref)
 		kl.recorder.Eventf(ref, "created", "Created with docker id %v", dockerContainer.ID)
 	}
 
@@ -993,7 +947,7 @@ func (kl *Kubelet) killContainerByID(ID string) error {
 	kl.readiness.remove(ID)
 	err := kl.dockerClient.StopContainer(ID, 10)
 
-	ref, ok := kl.getRef(ID)
+	ref, ok := kl.containerRefManager.GetRef(ID)
 	if !ok {
 		glog.Warningf("No ref for pod '%v'", ID)
 	} else {
@@ -1043,7 +997,7 @@ func (kl *Kubelet) createPodInfraContainer(pod *api.Pod) (dockertools.DockerID,
 		Image: kl.podInfraContainerImage,
 		Ports: ports,
 	}
-	ref, err := containerRef(pod, container)
+	ref, err := kl.containerRefManager.GenerateContainerRef(pod, container)
 	if err != nil {
 		glog.Errorf("Couldn't make a ref to pod %v, container %v: '%v'", pod.Name, container.Name, err)
 	}
@@ -1201,7 +1155,7 @@ func (kl *Kubelet) getPodInfraContainer(podFullName string, uid types.UID,
 func (kl *Kubelet) pullImageAndRunContainer(pod *api.Pod, container *api.Container, podVolumes *volumeMap,
 	podInfraContainerID dockertools.DockerID) (dockertools.DockerID, error) {
 	podFullName := kubecontainer.GetPodFullName(pod)
-	ref, err := containerRef(pod, container)
+	ref, err := kl.containerRefManager.GenerateContainerRef(pod, container)
 	if err != nil {
 		glog.Errorf("Couldn't make a ref to pod %v, container %v: '%v'", pod.Name, container.Name, err)
 	}

pkg/kubelet/kubelet_test.go

@@ -110,6 +110,7 @@ func newTestKubelet(t *testing.T) *TestKubelet {
 	kubelet.cadvisor = mockCadvisor
 	podManager, fakeMirrorClient := newFakePodManager()
 	kubelet.podManager = podManager
+	kubelet.containerRefManager = newContainerRefManager()
 	return &TestKubelet{kubelet, fakeDocker, mockCadvisor, fakeKubeClient, waitGroup, fakeMirrorClient}
 }
 

pkg/kubelet/probe.go

@@ -65,7 +65,7 @@ func (kl *Kubelet) probeContainer(pod *api.Pod, status api.PodStatus, container
 	glog.V(1).Infof("Readiness probe failed/errored: %v, %v", ready, err)
 	kl.readiness.set(containerID, false)
 
-	ref, ok := kl.getRef(containerID)
+	ref, ok := kl.containerRefManager.GetRef(containerID)
 	if !ok {
 		glog.Warningf("No ref for pod '%v' - '%v'", containerID, container.Name)
 	} else {

pkg/kubelet/probe_test.go

@@ -153,6 +153,7 @@ func makeTestKubelet(result probe.Result, err error) *Kubelet {
 				err:    err,
 			},
 		},
+		containerRefManager: newContainerRefManager(),
 	}
 }
 

pkg/kubelet/runonce_test.go

@@ -79,6 +79,7 @@ func TestRunOnce(t *testing.T) {
 		cadvisor:            cadvisor,
 		nodeLister:          testNodeLister{},
 		statusManager:       newStatusManager(nil),
+		containerRefManager: newContainerRefManager(),
 	}
 
 	kb.networkPlugin, _ = network.InitNetworkPlugin([]network.NetworkPlugin{}, "", network.NewFakeHost(nil))