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2010-02-16Stomp queue restructuring for mass scalability:Brion Vibber
- Multiplexing queues into groups and for multiple sites. - Sharing vs breakout configurable per site and per queue via $config['queue']['breakout'] - Detect how many times a message is redelivered, discard if it's killed too many daemons - count configurable with $config['queue']['max_retries'] - can dump the items to files in $config['queue']['dead_letter_dir'] Queue daemon memory & resource leak fixes: - avoid unnecessary reconnections to memcached server (switch persistent connections back in on second initialization, assuming it's child process) - monkey-patch for leaky .ini loads in DB_DataObject::databaseStructure() - was leaking 200k per active switch - applied leak fixes to Status_network as well, using intermediate base Safe_DataObject for both it and Memcache_DataObject Misc queue fixes: - correct handling of child processes exiting due to signal termination instead of regular exit - shutdown instead of infinite respawn loop if we're already past the soft memory limit at startup - Added --all option for xmppdaemon... still opens one xmpp connection per site that has xmpp active Cache updates: - add Cache::increment() method with native support for memcached atomic increment
2010-01-12Major refactoring of queue handlers to support running multiple sites in one ↵Brion Vibber
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