| // 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 |
| // |
| // 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 datastorecache implements a managed versatile datastore caching. |
| // Each datastorecache client obtains its own Cache instance for its specific |
| // cache type. That cache instance is given a "name" and managed independently |
| // from other cache types. |
| // |
| // Each cache instance additionally requires the configuration of a management |
| // cron task to handle that specific cache "name". This instance will require a |
| // handler to be registered for that cache name and a cron task configured to |
| // periodically hit that handler. |
| // |
| // Periodically, the management cron task will iterate through all cache entries |
| // and use their Handler to refresh those that are near expiration and delete |
| // those that haven't been used in a while. |
| // |
| // Manager Task |
| // |
| // The manager task runs periodically, triggered by cron. Each pass, it queries |
| // for all currently-registered cache entries and chooses an action: |
| // - If the entry hasn't been accessed in a while, it will be deleted. |
| // - If the entry references a Handler that isn't registered, it will be |
| // deleted eventually. |
| // - If the entry's "last refresh" timestamp is past its refresh period, it |
| // will be refreshed via its Handler. |
| // - Otherwise, the entry is left alone for the next pass. |
| // |
| // TODO: Each datastorecache cache is designed to be shard-able if the manager |
| // refresh ever becomes too burdensome for a single cron session. However, |
| // sharding isn't currently implemented. |
| package datastorecache |
