api_object_versioner.go

/*
Copyright 2014 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 etcd

import (
	"strconv"

	"k8s.io/apimachinery/pkg/api/meta"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apiserver/pkg/storage"
)

// APIObjectVersioner implements versioning and extracting etcd node information
// for objects that have an embedded ObjectMeta or ListMeta field.
type APIObjectVersioner struct{}

// UpdateObject implements Versioner
func (a APIObjectVersioner) UpdateObject(obj runtime.Object, resourceVersion uint64) error {
	accessor, err := meta.Accessor(obj)
	if err != nil {
		return err
	}
	versionString := ""
	if resourceVersion != 0 {
		versionString = strconv.FormatUint(resourceVersion, 10)
	}
	accessor.SetResourceVersion(versionString)
	return nil
}

// UpdateList implements Versioner
func (a APIObjectVersioner) UpdateList(obj runtime.Object, resourceVersion uint64, nextKey string) error {
	listAccessor, err := meta.ListAccessor(obj)
	if err != nil || listAccessor == nil {
		return err
	}
	versionString := ""
	if resourceVersion != 0 {
		versionString = strconv.FormatUint(resourceVersion, 10)
	}
	listAccessor.SetResourceVersion(versionString)
	listAccessor.SetContinue(nextKey)
	return nil
}

// PrepareObjectForStorage clears resource version and self link prior to writing to etcd.
func (a APIObjectVersioner) PrepareObjectForStorage(obj runtime.Object) error {
	accessor, err := meta.Accessor(obj)
	if err != nil {
		return err
	}
	accessor.SetResourceVersion("")
	accessor.SetSelfLink("")
	return nil
}

// ObjectResourceVersion implements Versioner
func (a APIObjectVersioner) ObjectResourceVersion(obj runtime.Object) (uint64, error) {
	accessor, err := meta.Accessor(obj)
	if err != nil {
		return 0, err
	}
	version := accessor.GetResourceVersion()
	if len(version) == 0 {
		return 0, nil
	}
	return strconv.ParseUint(version, 10, 64)
}

// APIObjectVersioner implements Versioner
var Versioner storage.Versioner = APIObjectVersioner{}

// CompareResourceVersion compares etcd resource versions.  Outside this API they are all strings,
// but etcd resource versions are special, they're actually ints, so we can easily compare them.
func (a APIObjectVersioner) CompareResourceVersion(lhs, rhs runtime.Object) int {
	lhsVersion, err := Versioner.ObjectResourceVersion(lhs)
	if err != nil {
		// coder error
		panic(err)
	}
	rhsVersion, err := Versioner.ObjectResourceVersion(rhs)
	if err != nil {
		// coder error
		panic(err)
	}

	if lhsVersion == rhsVersion {
		return 0
	}
	if lhsVersion < rhsVersion {
		return -1
	}

	return 1
}