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

1 files changed, 23 insertions, 0 deletions

diff --git a/classes/Memcached_DataObject.php b/classes/Memcached_DataObject.php
index 9c9994cea..4ecab9db6 100644
--- a/classes/Memcached_DataObject.php
+++ b/classes/Memcached_DataObject.php
@@ -331,6 +331,29 @@ class Memcached_DataObject extends DB_DataObject
             $exists = false;
        }
 
+        // @fixme horrible evil hack!
+        //
+        // In multisite configuration we don't want to keep around a separate
+        // connection for every database; we could end up with thousands of
+        // connections open per thread. In an ideal world we might keep
+        // a connection per server and select different databases, but that'd
+        // be reliant on having the same db username/pass as well.
+        //
+        // MySQL connections are cheap enough we're going to try just
+        // closing out the old connection and reopening when we encounter
+        // a new DSN.
+        //
+        // WARNING WARNING if we end up actually using multiple DBs at a time
+        // we'll need some fancier logic here.
+        if (!$exists && !empty($_DB_DATAOBJECT['CONNECTIONS'])) {
+            foreach ($_DB_DATAOBJECT['CONNECTIONS'] as $index => $conn) {
+                if (!empty($conn)) {
+                    $conn->disconnect();
+                }
+                unset($_DB_DATAOBJECT['CONNECTIONS'][$index]);
+            }
+        }
+        
         $result = parent::_connect();
 
         if ($result && !$exists) {