mirror of
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246 lines
11 KiB
Go
246 lines
11 KiB
Go
/*
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Copyright 2015 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package storage
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import (
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"context"
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"fmt"
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"k8s.io/apimachinery/pkg/api/meta"
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"k8s.io/apimachinery/pkg/fields"
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"k8s.io/apimachinery/pkg/labels"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/apimachinery/pkg/types"
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"k8s.io/apimachinery/pkg/watch"
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)
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// Versioner abstracts setting and retrieving metadata fields from database response
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// onto the object ot list. It is required to maintain storage invariants - updating an
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// object twice with the same data except for the ResourceVersion and SelfLink must be
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// a no-op. A resourceVersion of type uint64 is a 'raw' resourceVersion,
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// intended to be sent directly to or from the backend. A resourceVersion of
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// type string is a 'safe' resourceVersion, intended for consumption by users.
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type Versioner interface {
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// UpdateObject sets storage metadata into an API object. Returns an error if the object
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// cannot be updated correctly. May return nil if the requested object does not need metadata
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// from database.
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UpdateObject(obj runtime.Object, resourceVersion uint64) error
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// UpdateList sets the resource version into an API list object. Returns an error if the object
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// cannot be updated correctly. May return nil if the requested object does not need metadata from
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// database. continueValue is optional and indicates that more results are available if the client
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// passes that value to the server in a subsequent call. remainingItemCount indicates the number
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// of remaining objects if the list is partial. The remainingItemCount field is omitted during
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// serialization if it is set to nil.
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UpdateList(obj runtime.Object, resourceVersion uint64, continueValue string, remainingItemCount *int64) error
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// PrepareObjectForStorage should set SelfLink and ResourceVersion to the empty value. Should
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// return an error if the specified object cannot be updated.
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PrepareObjectForStorage(obj runtime.Object) error
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// ObjectResourceVersion returns the resource version (for persistence) of the specified object.
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// Should return an error if the specified object does not have a persistable version.
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ObjectResourceVersion(obj runtime.Object) (uint64, error)
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// ParseResourceVersion takes a resource version argument and
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// converts it to the storage backend. For watch we should pass to helper.Watch().
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// Because resourceVersion is an opaque value, the default watch
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// behavior for non-zero watch is to watch the next value (if you pass
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// "1", you will see updates from "2" onwards).
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ParseResourceVersion(resourceVersion string) (uint64, error)
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}
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// ResponseMeta contains information about the database metadata that is associated with
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// an object. It abstracts the actual underlying objects to prevent coupling with concrete
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// database and to improve testability.
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type ResponseMeta struct {
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// TTL is the time to live of the node that contained the returned object. It may be
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// zero or negative in some cases (objects may be expired after the requested
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// expiration time due to server lag).
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TTL int64
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// The resource version of the node that contained the returned object.
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ResourceVersion uint64
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}
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// IndexerFunc is a function that for a given object computes
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// <value of an index> for a particular <index>.
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type IndexerFunc func(obj runtime.Object) string
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// IndexerFuncs is a mapping from <index name> to function that
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// for a given object computes <value for that index>.
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type IndexerFuncs map[string]IndexerFunc
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// Everything accepts all objects.
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var Everything = SelectionPredicate{
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Label: labels.Everything(),
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Field: fields.Everything(),
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}
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// MatchValue defines a pair (<index name>, <value for that index>).
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type MatchValue struct {
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IndexName string
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Value string
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}
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// Pass an UpdateFunc to Interface.GuaranteedUpdate to make an update
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// that is guaranteed to succeed.
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// See the comment for GuaranteedUpdate for more details.
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type UpdateFunc func(input runtime.Object, res ResponseMeta) (output runtime.Object, ttl *uint64, err error)
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// ValidateObjectFunc is a function to act on a given object. An error may be returned
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// if the hook cannot be completed. The function may NOT transform the provided
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// object.
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type ValidateObjectFunc func(ctx context.Context, obj runtime.Object) error
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// ValidateAllObjectFunc is a "admit everything" instance of ValidateObjectFunc.
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func ValidateAllObjectFunc(ctx context.Context, obj runtime.Object) error {
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return nil
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}
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// Preconditions must be fulfilled before an operation (update, delete, etc.) is carried out.
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type Preconditions struct {
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// Specifies the target UID.
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// +optional
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UID *types.UID `json:"uid,omitempty"`
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// Specifies the target ResourceVersion
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// +optional
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ResourceVersion *string `json:"resourceVersion,omitempty"`
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}
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// NewUIDPreconditions returns a Preconditions with UID set.
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func NewUIDPreconditions(uid string) *Preconditions {
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u := types.UID(uid)
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return &Preconditions{UID: &u}
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}
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func (p *Preconditions) Check(key string, obj runtime.Object) error {
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if p == nil {
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return nil
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}
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objMeta, err := meta.Accessor(obj)
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if err != nil {
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return NewInternalErrorf(
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"can't enforce preconditions %v on un-introspectable object %v, got error: %v",
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*p,
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obj,
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err)
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}
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if p.UID != nil && *p.UID != objMeta.GetUID() {
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err := fmt.Sprintf(
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"Precondition failed: UID in precondition: %v, UID in object meta: %v",
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*p.UID,
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objMeta.GetUID())
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return NewInvalidObjError(key, err)
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}
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if p.ResourceVersion != nil && *p.ResourceVersion != objMeta.GetResourceVersion() {
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err := fmt.Sprintf(
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"Precondition failed: ResourceVersion in precondition: %v, ResourceVersion in object meta: %v",
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*p.ResourceVersion,
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objMeta.GetResourceVersion())
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return NewInvalidObjError(key, err)
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}
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return nil
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}
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// Interface offers a common interface for object marshaling/unmarshaling operations and
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// hides all the storage-related operations behind it.
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type Interface interface {
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// Returns Versioner associated with this interface.
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Versioner() Versioner
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// Create adds a new object at a key unless it already exists. 'ttl' is time-to-live
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// in seconds (0 means forever). If no error is returned and out is not nil, out will be
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// set to the read value from database.
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Create(ctx context.Context, key string, obj, out runtime.Object, ttl uint64) error
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// Delete removes the specified key and returns the value that existed at that spot.
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// If key didn't exist, it will return NotFound storage error.
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Delete(ctx context.Context, key string, out runtime.Object, preconditions *Preconditions, validateDeletion ValidateObjectFunc) error
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// Watch begins watching the specified key. Events are decoded into API objects,
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// and any items selected by 'p' are sent down to returned watch.Interface.
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// resourceVersion may be used to specify what version to begin watching,
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// which should be the current resourceVersion, and no longer rv+1
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// (e.g. reconnecting without missing any updates).
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// If resource version is "0", this interface will get current object at given key
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// and send it in an "ADDED" event, before watch starts.
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Watch(ctx context.Context, key string, resourceVersion string, p SelectionPredicate) (watch.Interface, error)
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// WatchList begins watching the specified key's items. Items are decoded into API
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// objects and any item selected by 'p' are sent down to returned watch.Interface.
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// resourceVersion may be used to specify what version to begin watching,
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// which should be the current resourceVersion, and no longer rv+1
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// (e.g. reconnecting without missing any updates).
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// If resource version is "0", this interface will list current objects directory defined by key
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// and send them in "ADDED" events, before watch starts.
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WatchList(ctx context.Context, key string, resourceVersion string, p SelectionPredicate) (watch.Interface, error)
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// Get unmarshals json found at key into objPtr. On a not found error, will either
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// return a zero object of the requested type, or an error, depending on ignoreNotFound.
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// Treats empty responses and nil response nodes exactly like a not found error.
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// The returned contents may be delayed, but it is guaranteed that they will
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// be have at least 'resourceVersion'.
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Get(ctx context.Context, key string, resourceVersion string, objPtr runtime.Object, ignoreNotFound bool) error
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// GetToList unmarshals json found at key and opaque it into *List api object
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// (an object that satisfies the runtime.IsList definition).
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// The returned contents may be delayed, but it is guaranteed that they will
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// be have at least 'resourceVersion'.
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GetToList(ctx context.Context, key string, resourceVersion string, p SelectionPredicate, listObj runtime.Object) error
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// List unmarshalls jsons found at directory defined by key and opaque them
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// into *List api object (an object that satisfies runtime.IsList definition).
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// The returned contents may be delayed, but it is guaranteed that they will
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// be have at least 'resourceVersion'.
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List(ctx context.Context, key string, resourceVersion string, p SelectionPredicate, listObj runtime.Object) error
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// GuaranteedUpdate keeps calling 'tryUpdate()' to update key 'key' (of type 'ptrToType')
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// retrying the update until success if there is index conflict.
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// Note that object passed to tryUpdate may change across invocations of tryUpdate() if
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// other writers are simultaneously updating it, so tryUpdate() needs to take into account
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// the current contents of the object when deciding how the update object should look.
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// If the key doesn't exist, it will return NotFound storage error if ignoreNotFound=false
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// or zero value in 'ptrToType' parameter otherwise.
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// If the object to update has the same value as previous, it won't do any update
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// but will return the object in 'ptrToType' parameter.
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// If 'suggestion' can contain zero or one element - in such case this can be used as
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// a suggestion about the current version of the object to avoid read operation from
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// storage to get it.
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//
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// Example:
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//
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// s := /* implementation of Interface */
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// err := s.GuaranteedUpdate(
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// "myKey", &MyType{}, true,
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// func(input runtime.Object, res ResponseMeta) (runtime.Object, *uint64, error) {
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// // Before each invocation of the user defined function, "input" is reset to
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// // current contents for "myKey" in database.
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// curr := input.(*MyType) // Guaranteed to succeed.
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//
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// // Make the modification
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// curr.Counter++
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//
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// // Return the modified object - return an error to stop iterating. Return
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// // a uint64 to alter the TTL on the object, or nil to keep it the same value.
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// return cur, nil, nil
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// },
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// )
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GuaranteedUpdate(
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ctx context.Context, key string, ptrToType runtime.Object, ignoreNotFound bool,
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precondtions *Preconditions, tryUpdate UpdateFunc, suggestion ...runtime.Object) error
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// Count returns number of different entries under the key (generally being path prefix).
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Count(key string) (int64, error)
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}
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