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 storage

import (
	"fmt"
	"strconv"

	"k8s.io/apimachinery/pkg/api/meta"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/util/validation/field"
)

// 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, count *int64) error {
	if resourceVersion == 0 {
		return fmt.Errorf("illegal resource version from storage: %d", resourceVersion)
	}
	listAccessor, err := meta.ListAccessor(obj)
	if err != nil || listAccessor == nil {
		return err
	}
	versionString := strconv.FormatUint(resourceVersion, 10)
	listAccessor.SetResourceVersion(versionString)
	listAccessor.SetContinue(nextKey)
	listAccessor.SetRemainingItemCount(count)
	return nil
}

// PrepareObjectForStorage clears resourceVersion and selfLink 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)
}

// ParseResourceVersion takes a resource version argument and converts it to
// the etcd version. For watch we should pass to helper.Watch(). Because resourceVersion is
// an opaque value, the default watch behavior for non-zero watch is to watch
// the next value (if you pass "1", you will see updates from "2" onwards).
func (a APIObjectVersioner) ParseResourceVersion(resourceVersion string) (uint64, error) {
	if resourceVersion == "" || resourceVersion == "0" {
		return 0, nil
	}
	version, err := strconv.ParseUint(resourceVersion, 10, 64)
	if err != nil {
		return 0, NewInvalidError(field.ErrorList{
			// Validation errors are supposed to return version-specific field
			// paths, but this is probably close enough.
			field.Invalid(field.NewPath("resourceVersion"), resourceVersion, err.Error()),
		})
	}
	return version, nil
}

// Versioner implements Versioner
var _ 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 := a.ObjectResourceVersion(lhs)
	if err != nil {
		// coder error
		panic(err)
	}
	rhsVersion, err := a.ObjectResourceVersion(rhs)
	if err != nil {
		// coder error
		panic(err)
	}

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

	return 1
}