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// Copyright 2016 The LUCI 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package datastorecache
import (
// entry is a single cached value.
// An entry is keyed on the hash of its Key via its PropertyLoadSaver.
type entry struct {
// Key is the cache entry's key, which uniquely identifies this cache entry.
// The Key for a given cache entry must be unique within that cache's
// Namespace and Name.
Key []byte `gae:",noindex"`
// CacheName is the name of the Cache that this entry belongs to. This can be
// empty.
CacheName string `gae:",noindex"`
// Created is the time when this entity was initially created.
Created time.Time `gae:",noindex"`
// LastAccessed is the last recorded access time for this entry. This is
// lazily updated, as its only operational requirement is to be a few times
// smaller than this entry's Handler's PruneInterval.
LastAccessed time.Time `gae:",noindex"`
// LastRefreshed is the last time that this entry was refreshed.
// The maintenance task will attempt to refresh this entry if its
// LastRefreshed time is near or outside of its Handler's RefreshInterval.
LastRefreshed time.Time `gae:",noindex"`
// LastRefreshDelta is a time.Duration representing the amount of time this
// entry took to refresh.
LastRefreshDelta int64
// Data is the entry's cached data.
Data []byte `gae:",noindex"`
// The cache Value's Schema (may be empty).
Schema string `gae:",noindex"`
// The cache Value's description string (may be empty).
Description string `gae:",noindex"`
// Retained key hash. We sync here so this is goroutine-safe. This will
// obviously not work if Key is changed in between hash calculations, but no
// code will do this.
initOnce sync.Once
calcKind string
calcKeyHash string
var _ datastore.MetaGetterSetter = (*entry)(nil)
func (e *entry) initialize() {
e.initOnce.Do(func() {
// Calculate our Kind.
kindParts := []string{"DSCacheEntry", ""}[:1]
cacheName := []byte(e.CacheName)
if len(cacheName) > 0 {
hash := sha256.Sum256(cacheName)
kindParts = append(kindParts, hex.EncodeToString(hash[:]))
e.calcKind = strings.Join(kindParts, "_")
// Calculate our key hash.
hash := sha256.New()
if len(cacheName) > 0 {
_, _ = hash.Write([]byte{0x00})
_, _ = hash.Write(cacheName)
_, _ = hash.Write(e.Key)
e.calcKeyHash = hex.EncodeToString(hash.Sum(nil))
// keyHash generates the hex-encoded entry hash. This incorporates the entry's
// CacheName (if present) and Kind.
func (e *entry) keyHash() string {
return e.calcKeyHash
func (e *entry) kind() string {
return e.calcKind
func (e *entry) toValue() Value {
return Value{
Schema: e.Schema,
Data: e.Data,
Description: e.Description,
func (e *entry) loadValue(v Value) {
e.Schema, e.Data, e.Description = v.Schema, v.Data, v.Description
func (e *entry) GetMeta(key string) (interface{}, bool) {
switch key {
case "kind":
return e.kind(), true
case "id":
return e.keyHash(), true
return datastore.GetPLS(e).GetMeta(key)
func (e *entry) GetAllMeta() datastore.PropertyMap {
return datastore.PropertyMap{
"$kind": datastore.MkProperty(e.kind()),
"$id": datastore.MkProperty(e.keyHash()),
func (e *entry) SetMeta(key string, val interface{}) bool {
return datastore.GetPLS(e).SetMeta(key, val)
func (e *entry) lockKey() string {
return "datastore_cache_entry_" + e.keyHash()
// managerShardStats are per-shard stats kept by manager runs.
type managerShardStats struct {
// Kind specifies the datastore entity kind.
Kind string `gae:"$kind,ManagerShardStats"`
// Shard is the shard ID for this stats entry.
Shard int `gae:"$id"`
// The last time that this manager was successfully run.
LastSuccessfulRun time.Time `gae:",noindex"`
// The total number of cache entries identified/handled in the last round.
LastEntryCount int `gae:",noindex"`