Add new metadata store.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/store/container/status.go

@@ -0,0 +1,146 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+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 container
+
+import (
+	"sync"
+
+	"k8s.io/kubernetes/pkg/kubelet/apis/cri/v1alpha1/runtime"
+)
+
+// TODO(random-liu): Handle versioning.
+// TODO(random-liu): Add checkpoint support.
+
+// version is current version of container status.
+const version = "v1" // nolint
+
+// versionedStatus is the internal used versioned container status.
+// nolint
+type versionedStatus struct {
+	// Version indicates the version of the versioned container status.
+	Version string
+	Status
+}
+
+// Status is the status of a container.
+type Status struct {
+	// Pid is the init process id of the container.
+	Pid uint32
+	// CreatedAt is the created timestamp.
+	CreatedAt int64
+	// StartedAt is the started timestamp.
+	StartedAt int64
+	// FinishedAt is the finished timestamp.
+	FinishedAt int64
+	// ExitCode is the container exit code.
+	ExitCode int32
+	// CamelCase string explaining why container is in its current state.
+	Reason string
+	// Human-readable message indicating details about why container is in its
+	// current state.
+	Message string
+	// Removing indicates that the container is in removing state.
+	// This field doesn't need to be checkpointed.
+	// TODO(random-liu): Reset this field to false during state recoverry.
+	Removing bool
+}
+
+// State returns current state of the container based on the container status.
+func (c Status) State() runtime.ContainerState {
+	if c.FinishedAt != 0 {
+		return runtime.ContainerState_CONTAINER_EXITED
+	}
+	if c.StartedAt != 0 {
+		return runtime.ContainerState_CONTAINER_RUNNING
+	}
+	if c.CreatedAt != 0 {
+		return runtime.ContainerState_CONTAINER_CREATED
+	}
+	return runtime.ContainerState_CONTAINER_UNKNOWN
+}
+
+// UpdateFunc is function used to update the container status. If there
+// is an error, the update will be rolled back.
+type UpdateFunc func(Status) (Status, error)
+
+// StatusStorage manages the container status with a storage backend.
+type StatusStorage interface {
+	// Get a container status.
+	Get() Status
+	// Update the container status. Note that the update MUST be applied
+	// in one transaction.
+	// TODO(random-liu): Distinguish `UpdateSync` and `Update`, only
+	// `UpdateSync` should sync data onto disk, so that disk operation
+	// for non-critical status change could be avoided.
+	Update(UpdateFunc) error
+	// Delete the container status.
+	// Note:
+	// * Delete should be idempotent.
+	// * The status must be deleted in one trasaction.
+	Delete() error
+}
+
+// TODO(random-liu): Add factory function and configure checkpoint path.
+
+// StoreStatus creates the storage containing the passed in container status with the
+// specified id.
+// The status MUST be created in one transaction.
+func StoreStatus(id string, status Status) (StatusStorage, error) {
+	return &statusStorage{status: status}, nil
+	// TODO(random-liu): Create the data on disk atomically.
+}
+
+// LoadStatus loads container status from checkpoint.
+func LoadStatus(id string) (StatusStorage, error) {
+	// TODO(random-liu): Load container status from disk.
+	return nil, nil
+}
+
+type statusStorage struct {
+	sync.RWMutex
+	status Status
+}
+
+// Get a copy of container status.
+func (m *statusStorage) Get() Status {
+	m.RLock()
+	defer m.RUnlock()
+	return m.status
+}
+
+// Update the container status.
+func (m *statusStorage) Update(u UpdateFunc) error {
+	m.Lock()
+	defer m.Unlock()
+	newStatus, err := u(m.status)
+	if err != nil {
+		return err
+	}
+	// TODO(random-liu) *Update* existing status on disk atomically,
+	// return error if checkpoint failed.
+	m.status = newStatus
+	return nil
+}
+
+// Delete deletes the container status from disk atomically.
+func (m *statusStorage) Delete() error {
+	// TODO(random-liu): Rename the data on the disk, returns error
+	// if fails. No lock is needed because file rename is atomic.
+	// TODO(random-liu): Cleanup temporary files generated, do not
+	// return error.
+	return nil
+}