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Diffstat (limited to 'lib/spawningdaemon.php')
| -rw-r--r-- | lib/spawningdaemon.php | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/lib/spawningdaemon.php b/lib/spawningdaemon.php new file mode 100644 index 000000000..8baefe88e --- /dev/null +++ b/lib/spawningdaemon.php @@ -0,0 +1,159 @@ +<?php +/* + * StatusNet - the distributed open-source microblogging tool + * Copyright (C) 2010, StatusNet, Inc. + * + * 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/>. + */ + +/** + * Base class for daemon that can launch one or more processing threads, + * respawning them if they exit. + * + * This is mainly intended for indefinite workloads such as monitoring + * a queue or maintaining an IM channel. + * + * Child classes should implement the + * + * We can then pass individual items through the QueueHandler subclasses + * they belong to. We additionally can handle queues for multiple sites. + * + * @package QueueHandler + * @author Brion Vibber <brion@status.net> + */ +abstract class SpawningDaemon extends Daemon +{ + protected $threads=1; + + function __construct($id=null, $daemonize=true, $threads=1) + { + parent::__construct($daemonize); + + if ($id) { + $this->set_id($id); + } + $this->threads = $threads; + } + + /** + * Perform some actual work! + * + * @return boolean true on success, false on failure + */ + public abstract function runThread(); + + /** + * Spawn one or more background processes and let them start running. + * Each individual process will execute whatever's in the runThread() + * method, which should be overridden. + * + * Child processes will be automatically respawned when they exit. + * + * @todo possibly allow for not respawning on "normal" exits... + * though ParallelizingDaemon is probably better for workloads + * that have forseeable endpoints. + */ + function run() + { + $children = array(); + for ($i = 1; $i <= $this->threads; $i++) { + $pid = pcntl_fork(); + if ($pid < 0) { + $this->log(LOG_ERROR, "Couldn't fork for thread $i; aborting\n"); + exit(1); + } else if ($pid == 0) { + $this->initAndRunChild($i); + } else { + $this->log(LOG_INFO, "Spawned thread $i as pid $pid"); + $children[$i] = $pid; + } + } + + $this->log(LOG_INFO, "Waiting for children to complete."); + while (count($children) > 0) { + $status = null; + $pid = pcntl_wait($status); + if ($pid > 0) { + $i = array_search($pid, $children); + if ($i === false) { + $this->log(LOG_ERR, "Unrecognized child pid $pid exited!"); + continue; + } + unset($children[$i]); + $this->log(LOG_INFO, "Thread $i pid $pid exited."); + + $pid = pcntl_fork(); + if ($pid < 0) { + $this->log(LOG_ERROR, "Couldn't fork to respawn thread $i; aborting thread.\n"); + } else if ($pid == 0) { + $this->initAndRunChild($i); + } else { + $this->log(LOG_INFO, "Respawned thread $i as pid $pid"); + $children[$i] = $pid; + } + } + } + $this->log(LOG_INFO, "All child processes complete."); + return true; + } + + /** + * Initialize things for a fresh thread, call runThread(), and + * exit at completion with appropriate return value. + */ + protected function initAndRunChild($thread) + { + $this->set_id($this->get_id() . "." . $thread); + $this->resetDb(); + $ok = $this->runThread(); + exit($ok ? 0 : 1); + } + + /** + * Reconnect to the database for each child process, + * or they'll get very confused trying to use the + * same socket. + */ + protected function resetDb() + { + // @fixme do we need to explicitly open the db too + // or is this implied? + global $_DB_DATAOBJECT; + unset($_DB_DATAOBJECT['CONNECTIONS']); + + // Reconnect main memcached, or threads will stomp on + // each other and corrupt their requests. + $cache = common_memcache(); + if ($cache) { + $cache->reconnect(); + } + + // Also reconnect memcached for status_network table. + if (!empty(Status_network::$cache)) { + Status_network::$cache->close(); + Status_network::$cache = null; + } + } + + function log($level, $msg) + { + common_log($level, get_class($this) . ' ('. $this->get_id() .'): '.$msg); + } + + function name() + { + return strtolower(get_class($this).'.'.$this->get_id()); + } +} + |