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, 6 insertions, 3 deletions

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);