gnu-social/plugins/MemcachePlugin.php

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<?php
/**
* StatusNet - the distributed open-source microblogging tool
* Copyright (C) 2009, StatusNet, Inc.
*
* Plugin to implement cache interface for memcache
*
* 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 Cache
* @package StatusNet
* @author Evan Prodromou <evan@status.net>
* @copyright 2009 StatusNet, Inc.
* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 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);
}
/**
* A plugin to use memcache for the cache interface
*
* This used to be encoded as config-variable options in the core code;
* it's now broken out to a separate plugin. The same interface can be
* implemented by other plugins.
*
* @category Cache
* @package StatusNet
* @author Evan Prodromou <evan@status.net>
* @copyright 2009 StatusNet, Inc.
* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
* @link http://status.net/
*/
class MemcachePlugin extends Plugin
{
static $cacheInitialized = false;
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private $_conn = null;
public $servers = array('127.0.0.1;11211');
public $compressThreshold = 20480;
public $compressMinSaving = 0.2;
public $persistent = null;
public $defaultExpiry = 86400; // 24h
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/**
* Initialize the plugin
*
* Note that onStartCacheGet() may have been called before this!
*
* @return boolean flag value
*/
function onInitializePlugin()
{
if (self::$cacheInitialized) {
$this->persistent = true;
} else {
// If we're a parent command-line process we need
// to be able to close out the connection after
// forking, so disable persistence.
//
// We'll turn it back on again the second time
// through which will either be in a child process,
// or a single-process script which is switching
// configurations.
$this->persistent = (php_sapi_name() == 'cli') ? false : true;
}
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$this->_ensureConn();
self::$cacheInitialized = true;
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return true;
}
/**
* Get a value associated with a key
*
* The value should have been set previously.
*
* @param string &$key in; Lookup key
* @param mixed &$value out; value associated with key
*
* @return boolean hook success
*/
function onStartCacheGet(&$key, &$value)
{
$this->_ensureConn();
$value = $this->_conn->get($key);
Event::handle('EndCacheGet', array($key, &$value));
return false;
}
/**
* Associate a value with a key
*
* @param string &$key in; Key to use for lookups
* @param mixed &$value in; Value to associate
* @param integer &$flag in; Flag empty or Cache::COMPRESSED
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* @param integer &$expiry in; Expiry (passed through to Memcache)
* @param boolean &$success out; Whether the set was successful
*
* @return boolean hook success
*/
function onStartCacheSet(&$key, &$value, &$flag, &$expiry, &$success)
{
$this->_ensureConn();
if ($expiry === null) {
$expiry = $this->defaultExpiry;
}
$success = $this->_conn->set($key, $value, $this->flag(intval($flag)), $expiry);
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Event::handle('EndCacheSet', array($key, $value, $flag,
$expiry));
return false;
}
/**
* Atomically increment an existing numeric key value.
* Existing expiration time will not be changed.
*
* @param string &$key in; Key to use for lookups
* @param int &$step in; Amount to increment (default 1)
* @param mixed &$value out; Incremented value, or false if key not set.
*
* @return boolean hook success
*/
function onStartCacheIncrement(&$key, &$step, &$value)
{
$this->_ensureConn();
$value = $this->_conn->increment($key, $step);
Event::handle('EndCacheIncrement', array($key, $step, $value));
return false;
}
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/**
* Delete a value associated with a key
*
* @param string &$key in; Key to lookup
* @param boolean &$success out; whether it worked
*
* @return boolean hook success
*/
function onStartCacheDelete(&$key, &$success)
{
$this->_ensureConn();
$success = $this->_conn->delete($key);
Event::handle('EndCacheDelete', array($key));
return false;
}
Major refactoring of queue handlers to support running multiple sites in one daemon. Key changes: * Initialization code moved from common.php to StatusNet class; can now switch configurations during runtime. * As a consequence, configuration files must now be idempotent... Be careful with constant, function or class definitions. * Control structure for daemons/QueueManager/QueueHandler has been refactored; the run loop is now managed by IoMaster run via scripts/queuedaemon.php IoManager subclasses are woken to handle socket input or polling, and may cover multiple sites. * Plugins can implement notice queue handlers more easily by registering a QueueHandler class; no more need to add a daemon. The new QueueDaemon runs from scripts/queuedaemon.php: * This replaces most of the old *handler.php scripts; they've been refactored to the bare handler classes. * Spawns multiple child processes to spread load; defaults to CPU count on Linux and Mac OS X systems, or override with --threads=N * When multithreaded, child processes are automatically respawned on failure. * Threads gracefully shut down and restart when passing a soft memory limit (defaults to 90% of memory_limit), limiting damage from memory leaks. * Support for UDP-based monitoring: http://www.gitorious.org/snqmon Rough control flow diagram: QueueDaemon -> IoMaster -> IoManager QueueManager [listen or poll] -> QueueHandler XmppManager [ping & keepalive] XmppConfirmManager [poll updates] Todo: * Respawning features not currently available running single-threaded. * When running single-site, configuration changes aren't picked up. * New sites or config changes affecting queue subscriptions are not yet handled without a daemon restart. * SNMP monitoring output to integrate with general tools (nagios, ganglia) * Convert XMPP confirmation message sends to use stomp queue instead of polling * Convert xmppdaemon.php to IoManager? * Convert Twitter status, friends import polling daemons to IoManager * Clean up some error reporting and failure modes * May need to adjust queue priorities for best perf in backlog/flood cases Detailed code history available in my daemon-work branch: http://www.gitorious.org/~brion/statusnet/brion-fixes/commits/daemon-work
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function onStartCacheReconnect(&$success)
{
if (empty($this->_conn)) {
// nothing to do
return true;
}
if ($this->persistent) {
common_log(LOG_ERR, "Cannot close persistent memcached connection");
$success = false;
} else {
common_log(LOG_INFO, "Closing memcached connection");
$success = $this->_conn->close();
$this->_conn = null;
}
return false;
}
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/**
* Ensure that a connection exists
*
* Checks the instance $_conn variable and connects
* if it is empty.
*
* @return void
*/
private function _ensureConn()
{
if (empty($this->_conn)) {
$this->_conn = new Memcache();
if (is_array($this->servers)) {
$servers = $this->servers;
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} else {
$servers = array($this->servers);
}
foreach ($servers as $server) {
if (strpos($server, ';') !== false) {
list($host, $port) = explode(';', $server);
} else {
$host = $server;
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$port = 11211;
}
$this->_conn->addServer($host, $port, $this->persistent);
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}
// Compress items stored in the cache if they're over threshold in size
// (default 2KiB) and the compression would save more than min savings
// ratio (default 0.2).
// Allows the cache to store objects larger than 1MB (if they
// compress to less than 1MB), and improves cache memory efficiency.
$this->_conn->setCompressThreshold($this->compressThreshold,
$this->compressMinSaving);
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}
}
/**
* Translate general flags to Memcached-specific flags
* @param int $flag
* @return int
*/
protected function flag($flag)
{
$out = 0;
if ($flag & Cache::COMPRESSED == Cache::COMPRESSED) {
$out |= MEMCACHE_COMPRESSED;
}
return $out;
}
function onPluginVersion(&$versions)
{
$versions[] = array('name' => 'Memcache',
'version' => STATUSNET_VERSION,
'author' => 'Evan Prodromou, Craig Andrews',
'homepage' => 'http://status.net/wiki/Plugin:Memcache',
'rawdescription' =>
_m('Use <a href="http://memcached.org/">Memcached</a> to cache query results.'));
return true;
}
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}