sam marshall
8ddfa20121
A list of times for each cache key in a TTL cache is kept in a Redis sorted list, which can be queried efficiently to delete expired cache items later in a scheduled task. This change makes set and delete 2x slower (only for caches which use TTL) but there is no impact on get performance.
106 lines
4.3 KiB
PHP
106 lines
4.3 KiB
PHP
<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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namespace cachestore_redis\task;
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/**
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* Task deletes old data from Redis caches with TTL set.
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*
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* @package cachestore_redis
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* @copyright 2021 The Open University
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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class ttl extends \core\task\scheduled_task {
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/** @var int Only display memory savings of at least 100 KB */
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const MIN_MEMORY_SIZE = 100 * 1024;
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/**
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* Gets the name of this task.
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*
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* @return string Task name
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*/
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public function get_name(): string {
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return get_string('task_ttl', 'cachestore_redis');
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}
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/**
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* Executes the scheduled task.
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*/
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public function execute(): void {
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// Find all Redis cache stores.
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$factory = \cache_factory::instance();
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$config = $factory->create_config_instance();
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$stores = $config->get_all_stores();
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$doneanything = false;
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foreach ($stores as $storename => $storeconfig) {
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if ($storeconfig['plugin'] !== 'redis') {
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continue;
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}
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// For each definition in the cache store, do TTL expiry if needed.
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$definitions = $config->get_definitions_by_store($storename);
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foreach ($definitions as $definition) {
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if (empty($definition['ttl'])) {
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continue;
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}
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if (!empty($definition['requireidentifiers'])) {
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// We can't make cache below if it requires identifiers.
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continue;
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}
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$doneanything = true;
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$definitionname = $definition['component'] . '/' . $definition['area'];
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mtrace($definitionname, ': ');
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\cache::make($definition['component'], $definition['area']);
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$definition = $factory->create_definition($definition['component'], $definition['area']);
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$stores = $factory->get_store_instances_in_use($definition);
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foreach ($stores as $store) {
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// These were all definitions using a Redis store but one definition may
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// potentially have multiple stores, we need to process the Redis ones only.
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if (!($store instanceof \cachestore_redis)) {
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continue;
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}
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$info = $store->expire_ttl();
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$infotext = 'Deleted ' . $info['keys'] . ' key(s) in ' .
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sprintf('%0.2f', $info['time']) . 's';
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// Only report memory information if available, positive, and reasonably large.
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// Otherwise the real information is hard to see amongst random variation etc.
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if (!empty($info['memory']) && $info['memory'] > self::MIN_MEMORY_SIZE) {
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$infotext .= ' - reported saving ' . display_size($info['memory']);
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}
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mtrace($infotext);
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}
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}
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}
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if (!$doneanything) {
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mtrace('No TTL caches assigned to a Redis store; nothing to do.');
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}
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}
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/**
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* Checks if this task is allowed to run - this makes it show the 'Run now' link (or not).
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*
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* @return bool True if task can run
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*/
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public function can_run(): bool {
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// The default implementation of this function checks the plugin is enabled, which doesn't
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// seem to work (probably because cachestore plugins can't be enabled).
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// We could check if there is a Redis store configured, but it would have to do the exact
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// same logic as already in the first part of 'execute', so it's probably OK to just return
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// true.
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return true;
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}
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}
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