gnu-social/lib/cache.php

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<?php
/**
* StatusNet, the distributed open-source microblogging tool
*
* Cache interface plus default in-memory cache implementation
*
* PHP version 5
*
* LICENCE: 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/
*/
/**
* Interface for caching
*
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* An abstract interface for caching. Because we originally used the
* Memcache plugin directly, the interface uses a small subset of the
* Memcache interface.
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*
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* @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 AGPL 3.0
* @link http://status.net/
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*/
class Cache
{
/**
* @var array additional in-process cache for web requests;
* disabled on CLI, unsafe for long-running daemons
*/
var $_items = array();
var $_inlineCache = true;
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static $_inst = null;
const COMPRESSED = 1;
private function __construct() {
// Potentially long-running daemons or maintenance scripts
// should not use an in-process cache as it becomes out of
// date.
$this->_inlineCache = (php_sapi_name() != 'cli');
}
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/**
* Singleton constructor
*
* Use this to get the singleton instance of Cache.
*
* @return Cache cache object
*/
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static function instance()
{
if (is_null(self::$_inst)) {
self::$_inst = new Cache();
}
return self::$_inst;
}
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/**
* Create a cache key from input text
*
* Builds a cache key from input text. Helps to namespace
* the cache area (if shared with other applications or sites)
* and prevent conflicts.
*
* @param string $extra the real part of the key
*
* @return string full key
*/
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static function key($extra)
{
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$base_key = common_config('cache', 'base');
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if (empty($base_key)) {
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$base_key = self::keyize(common_config('site', 'name'));
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}
return 'statusnet:' . $base_key . ':' . $extra;
}
/**
* Create a cache key for data dependent on code
*
* For cache elements that are dependent on changes in code, this creates
* a more-or-less fingerprint of the current running code and adds it to
* the cache key. In the case of an upgrade of core, or addition or
* removal of plugins, a new unique fingerprint is generated and used.
*
* There can still be problems with a) differences in versions of the
* plugins and b) people running code between official versions. This is
* usually a problem only for experienced users like developers, who know
* how to clear their cache.
*
* For sites that run code between versions (like the status.net cloud),
* there's an additional build number configuration setting.
*
* @param string $extra the real part of the key
*
* @return string full key
*/
static function codeKey($extra)
{
static $prefix = null;
if (empty($prefix)) {
$plugins = StatusNet::getActivePlugins();
$names = array();
foreach ($plugins as $plugin) {
$names[] = $plugin[0];
}
$names = array_unique($names);
asort($names);
// Unique enough.
$uniq = crc32(implode(',', $names));
$build = common_config('site', 'build');
$prefix = STATUSNET_VERSION.':'.$build.':'.$uniq;
}
return Cache::key($prefix.':'.$extra);
}
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/**
* Make a string suitable for use as a key
*
* Useful for turning primary keys of tables into cache keys.
*
* @param string $str string to turn into a key
*
* @return string keyized string
*/
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static function keyize($str)
{
$str = strtolower($str);
$str = preg_replace('/\s/', '_', $str);
return $str;
}
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/**
* Get a value associated with a key
*
* The value should have been set previously.
*
* @param string $key Lookup key
*
* @return string retrieved value or null if unfound
*/
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function get($key)
{
$value = false;
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common_perf_counter('Cache::get', $key);
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if (Event::handle('StartCacheGet', array(&$key, &$value))) {
if ($this->_inlineCache && array_key_exists($key, $this->_items)) {
$value = unserialize($this->_items[$key]);
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}
Event::handle('EndCacheGet', array($key, &$value));
}
return $value;
}
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/**
* Set the value associated with a key
*
* @param string $key The key to use for lookups
* @param string $value The value to store
* @param integer $flag Flags to use, may include Cache::COMPRESSED
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* @param integer $expiry Expiry value, mostly ignored
*
* @return boolean success flag
*/
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function set($key, $value, $flag=null, $expiry=null)
{
$success = false;
common_perf_counter('Cache::set', $key);
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if (Event::handle('StartCacheSet', array(&$key, &$value, &$flag,
&$expiry, &$success))) {
if ($this->_inlineCache) {
$this->_items[$key] = serialize($value);
}
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$success = true;
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Event::handle('EndCacheSet', array($key, $value, $flag,
$expiry));
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}
return $success;
}
/**
* Atomically increment an existing numeric value.
* Existing expiration time should remain unchanged, if any.
*
* @param string $key The key to use for lookups
* @param int $step Amount to increment (default 1)
*
* @return mixed incremented value, or false if not set.
*/
function increment($key, $step=1)
{
$value = false;
common_perf_counter('Cache::increment', $key);
if (Event::handle('StartCacheIncrement', array(&$key, &$step, &$value))) {
// Fallback is not guaranteed to be atomic,
// and may original expiry value.
$value = $this->get($key);
if ($value !== false) {
$value += $step;
$ok = $this->set($key, $value);
$got = $this->get($key);
}
Event::handle('EndCacheIncrement', array($key, $step, $value));
}
return $value;
}
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/**
* Delete the value associated with a key
*
* @param string $key Key to delete
*
* @return boolean success flag
*/
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function delete($key)
{
$success = false;
common_perf_counter('Cache::delete', $key);
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if (Event::handle('StartCacheDelete', array(&$key, &$success))) {
if ($this->_inlineCache && array_key_exists($key, $this->_items)) {
unset($this->_items[$key]);
}
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$success = true;
Event::handle('EndCacheDelete', array($key));
}
return $success;
}
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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/**
* Close or reconnect any remote connections, such as to give
* daemon processes a chance to reconnect on a fresh socket.
*
* @return boolean success flag
*/
function reconnect()
{
$success = false;
if (Event::handle('StartCacheReconnect', array(&$success))) {
$success = true;
Event::handle('EndCacheReconnect', array());
}
return $success;
}
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}