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

3 files changed, 49 insertions, 6 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) {
diff --git a/classes/Queue_item.php b/classes/Queue_item.php
index 9c673540d..cf805a606 100644
--- a/classes/Queue_item.php
+++ b/classes/Queue_item.php
@@ -25,10 +25,12 @@ class Queue_item extends Memcached_DataObject
     function sequenceKey()
     { return array(false, false); }
 
-    static function top($transport) {
+    static function top($transport=null) {
 
         $qi = new Queue_item();
-        $qi->transport = $transport;
+        if ($transport) {
+            $qi->transport = $transport;
+        }
         $qi->orderBy('created');
         $qi->whereAdd('claimed is null');
 
@@ -40,7 +42,8 @@ class Queue_item extends Memcached_DataObject
             # XXX: potential race condition
             # can we force it to only update if claimed is still null
             # (or old)?
-            common_log(LOG_INFO, 'claiming queue item = ' . $qi->notice_id . ' for transport ' . $transport);
+            common_log(LOG_INFO, 'claiming queue item = ' . $qi->notice_id .
+                ' for transport ' . $qi->transport);
             $orig = clone($qi);
             $qi->claimed = common_sql_now();
             $result = $qi->update($orig);
diff --git a/classes/Status_network.php b/classes/Status_network.php
index 776f6abb0..ef8e1ed43 100644
--- a/classes/Status_network.php
+++ b/classes/Status_network.php
@@ -49,6 +49,13 @@ class Status_network extends DB_DataObject
     static $cache = null;
     static $base = null;
 
+    /**
+     * @param string $dbhost
+     * @param string $dbuser
+     * @param string $dbpass
+     * @param string $dbname
+     * @param array $servers memcached servers to use for caching config info
+     */
     static function setupDB($dbhost, $dbuser, $dbpass, $dbname, $servers)
     {
         global $config;
@@ -60,12 +67,17 @@ class Status_network extends DB_DataObject
         if (class_exists('Memcache')) {
             self::$cache = new Memcache();
 
+            // Can't close persistent connections, making forking painful.
+            //
+            // @fixme only do this in *parent* CLI processes.
+            // single-process and child-processes *should* use persistent.
+            $persist = php_sapi_name() != 'cli';
             if (is_array($servers)) {
                 foreach($servers as $server) {
-                    self::$cache->addServer($server);
+                    self::$cache->addServer($server, 11211, $persist);
                 }
             } else {
-                self::$cache->addServer($servers);
+                self::$cache->addServer($servers, 11211, $persist);
             }
         }
 
@@ -89,7 +101,7 @@ class Status_network extends DB_DataObject
         if (empty($sn)) {
             $sn = self::staticGet($k, $v);
             if (!empty($sn)) {
-                self::$cache->set($ck, $sn);
+                self::$cache->set($ck, clone($sn));
             }
         }
 
@@ -121,6 +133,11 @@ class Status_network extends DB_DataObject
         return parent::delete();
     }
 
+    /**
+     * @param string $servername hostname
+     * @param string $pathname URL base path
+     * @param string $wildcard hostname suffix to match wildcard config
+     */
     static function setupSite($servername, $pathname, $wildcard)
     {
         global $config;