gnu-social/lib/notices/cachingnoticestream.php

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<?php
// This file is part of GNU social - https://www.gnu.org/software/social
//
// GNU social is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// GNU social is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with GNU social. If not, see <http://www.gnu.org/licenses/>.
/**
* A stream of notices
*
* @category Stream
* @package GNUsocial
* @author Evan Prodromou <evan@status.net>
* @copyright 2011 StatusNet, Inc.
* @license https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
*/
defined('GNUSOCIAL') || die();
/**
* Class for notice streams
*
* @category Stream
* @package GNUsocial
* @author Evan Prodromou <evan@status.net>
* @copyright 2011 StatusNet, Inc.
* @license https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
*/
class CachingNoticeStream extends NoticeStream
{
const CACHE_WINDOW = 200;
public $stream = null;
public $cachekey = null;
public $useLast = true;
public $alwaysCheck = true;
public function __construct(
NoticeStream $stream,
string $cachekey,
bool $useLast = true,
bool $alwaysCheck = false
) {
$this->stream = $stream;
$this->cachekey = $cachekey;
$this->useLast = $useLast;
$this->alwaysCheck = $alwaysCheck;
}
private function getCacheNoticeIds(
Cache $cache,
string $idkey,
bool $check = false
): ?array {
$id_str = $cache->get($idkey);
if ($id_str === false) {
return null;
}
$ids = explode(',', $id_str);
if ($check) {
$latest_id = $ids[0];
$new_ids = $this->stream->getNoticeIds(
0,
self::CACHE_WINDOW,
$latest_id,
null
);
$ids = array_merge($new_ids, $ids);
$ids = array_slice($ids, 0, self::CACHE_WINDOW);
$new_id_str = implode(',', $ids);
if ($id_str !== $new_id_str) {
$cache->set($idkey, $new_id_str);
}
}
return $ids;
}
public function getNoticeIds($offset, $limit, $sinceId, $maxId)
{
$cache = Cache::instance();
// We cache self::CACHE_WINDOW elements at the tip of the stream.
// If the cache won't be hit, just generate directly.
if (empty($cache) ||
$sinceId != 0 || $maxId != 0 ||
is_null($limit) ||
($offset + $limit) > self::CACHE_WINDOW) {
return $this->stream->getNoticeIds($offset, $limit, $sinceId, $maxId);
}
// Check the cache to see if we have the stream.
$idkey = Cache::key($this->cachekey);
$ids = $this->getCacheNoticeIds($cache, $idkey, $this->alwaysCheck);
if (!is_null($ids)) {
// Cache hit! Woohoo!
return array_slice($ids, $offset, $limit);
}
if ($this->useLast) {
// Check the cache to see if we have a "last-known-good" version.
// The actual cache gets blown away when new notices are added, but
// the "last" value holds a lot of info. We might need to only generate
// a few at the "tip", which can bound our queries and save lots
// of time.
$ids = $this->getCacheNoticeIds($cache, $idkey . ';last', true);
if (!is_null($ids)) {
// Set the actual cache value as well
$id_str = implode(',', $ids);
$cache->set($idkey, $id_str);
return array_slice($ids, $offset, $limit);
}
}
// No cache hits :( Generate directly and stick the results
// into the cache. Note we generate the full cache window.
$window = $this->stream->getNoticeIds(0, self::CACHE_WINDOW, null, null);
$windowstr = implode(',', $window);
$cache->set($idkey, $windowstr);
if ($this->useLast) {
$cache->set($idkey . ';last', $windowstr);
}
// Return just the slice that was requested
return array_slice($window, $offset, $limit);
}
}