gnu-social/lib/cachingnoticestream.php

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<?php
/**
* StatusNet - the distributed open-source microblogging tool
* Copyright (C) 2011, StatusNet, Inc.
*
* A stream of notices
*
* PHP version 5
*
* This program 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.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*
* @category Stream
* @package StatusNet
* @author Evan Prodromou <evan@status.net>
* @copyright 2011 StatusNet, Inc.
* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
* @link http://status.net/
*/
if (!defined('STATUSNET')) {
// This check helps protect against security problems;
// your code file can't be executed directly from the web.
exit(1);
}
/**
* Class for notice streams
*
* @category Stream
* @package StatusNet
* @author Evan Prodromou <evan@status.net>
* @copyright 2011 StatusNet, Inc.
* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
* @link http://status.net/
*/
class CachingNoticeStream extends NoticeStream
{
const CACHE_WINDOW = 200;
public $stream = null;
public $cachekey = null;
public $useLast = true;
function __construct($stream, $cachekey, $useLast = true)
{
$this->stream = $stream;
$this->cachekey = $cachekey;
$this->useLast = $useLast;
}
function getNoticeIds($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);
$idstr = $cache->get($idkey);
if ($idstr !== false) {
// Cache hit! Woohoo!
$window = explode(',', $idstr);
$ids = array_slice($window, $offset, $limit);
return $ids;
}
if ($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.
$laststr = $cache->get($idkey.';last');
if ($laststr !== false) {
$window = explode(',', $laststr);
$last_id = $window[0];
$new_ids = $this->stream->getNoticeIds(0, self::CACHE_WINDOW, $last_id, 0);
$new_window = array_merge($new_ids, $window);
$new_windowstr = implode(',', $new_window);
$result = $cache->set($idkey, $new_windowstr);
$result = $cache->set($idkey . ';last', $new_windowstr);
$ids = array_slice($new_window, $offset, $limit);
return $ids;
}
}
// 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, 0, 0);
$windowstr = implode(',', $window);
$result = $cache->set($idkey, $windowstr);
if ($this->useLast) {
$result = $cache->set($idkey . ';last', $windowstr);
}
// Return just the slice that was requested
$ids = array_slice($window, $offset, $limit);
return $ids;
}
}