Stomp queue restructuring for mass scalability:

- 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

plugins/MemcachePlugin.php

@@ -51,6 +51,8 @@ if (!defined('STATUSNET')) {
 
 class MemcachePlugin extends Plugin
 {
+    static $cacheInitialized = false;
+
     private $_conn  = null;
     public $servers = array('127.0.0.1;11211');
 
@@ -71,10 +73,21 @@ class MemcachePlugin extends Plugin
 
     function onInitializePlugin()
     {
-        if (is_null($this->persistent)) {
+        if (self::$cacheInitialized) {
+            $this->persistent = true;
+        } else {
+            // If we're a parent command-line process we need
+            // to be able to close out the connection after
+            // forking, so disable persistence.
+            //
+            // We'll turn it back on again the second time
+            // through which will either be in a child process,
+            // or a single-process script which is switching
+            // configurations.
             $this->persistent = (php_sapi_name() == 'cli') ? false : true;
         }
         $this->_ensureConn();
+        self::$cacheInitialized = true;
         return true;
     }
 
@@ -121,6 +134,24 @@ class MemcachePlugin extends Plugin
         return false;
     }
 
+    /**
+     * Atomically increment an existing numeric key value.
+     * Existing expiration time will not be changed.
+     *
+     * @param string &$key    in; Key to use for lookups
+     * @param int    &$step   in; Amount to increment (default 1)
+     * @param mixed  &$value  out; Incremented value, or false if key not set.
+     *
+     * @return boolean hook success
+     */
+    function onStartCacheIncrement(&$key, &$step, &$value)
+    {
+        $this->_ensureConn();
+        $value = $this->_conn->increment($key, $step);
+        Event::handle('EndCacheIncrement', array($key, $step, $value));
+        return false;
+    }
+
     /**
      * Delete a value associated with a key
      *