From 6d29592ec7a37f907256c18aff4afe9cab74d987 Mon Sep 17 00:00:00 2001
From: Zach Copley <zach@controlyourself.ca>
Date: Thu, 6 Aug 2009 01:15:08 +0000
Subject: [PATCH] Abstract out the parallelizing daemon stuff

---
 lib/parallelizingdaemon.php | 225 ++++++++++++++++++++++++++++++++++++
 1 file changed, 225 insertions(+)
 create mode 100644 lib/parallelizingdaemon.php

diff --git a/lib/parallelizingdaemon.php b/lib/parallelizingdaemon.php
new file mode 100644
index 0000000000..5ecfd98f33
--- /dev/null
+++ b/lib/parallelizingdaemon.php
@@ -0,0 +1,225 @@
+<?php
+/**
+ * Laconica, the distributed open-source microblogging tool
+ *
+ * Base class for making daemons that can do several tasks in parallel.
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  Daemon
+ * @package   Laconica
+ * @author    Zach Copley <zach@controlyourself.ca>
+ * @author    Evan Prodromou <evan@controlyourself.ca>
+ * @copyright 2009 Control Yourself, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link      http://laconi.ca/
+ */
+
+if (!defined('LACONICA')) {
+    exit(1);
+}
+
+declare(ticks = 1);
+
+/**
+ * Daemon able to spawn multiple child processes to do work in parallel
+ *
+ * @category Daemon
+ * @package  Laconica
+ * @author   Zach Copley <zach@controlyourself.ca>
+ * @author   Evan Prodromou <evan@controlyourself.ca>
+ * @license  http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link     http://laconi.ca/
+ */
+
+class ParallelizingDaemon extends Daemon
+{
+    private $_children     = array();
+    private $_interval     = 0; // seconds
+    private $_max_children = 0; // maximum number of children
+    private $_debug        = false;
+
+    /**
+     *  Constructor
+     *
+     * @param string  $id           the name/id of this daemon
+     * @param int     $interval     sleep this long before doing everything again
+     * @param int     $max_children maximum number of child processes at a time
+     * @param boolean $debug        debug output flag
+     *
+     * @return void
+     *
+     **/
+
+    function __construct($id = null, $interval = 60, $max_children = 2,
+                         $debug = null)
+    {
+        parent::__construct(true); // daemonize
+
+        $this->_interval     = $interval;
+        $this->_max_children = $max_children;
+        $this->_debug        = $debug;
+
+        if (isset($id)) {
+            $this->set_id($id);
+        }
+    }
+
+    /**
+     * Run the daemon
+     *
+     * @return void
+     */
+
+    function run()
+    {
+        if (isset($this->_debug)) {
+            echo $this->name() . " - debugging output enabled.\n";
+        }
+
+        do {
+
+            $objects = $this->getObjects();
+
+            foreach ($objects as $o) {
+
+                // Fork a child for each object
+
+                $pid = pcntl_fork();
+
+                if ($pid == -1) {
+                    die ($this->name() . ' - Couldn\'t fork!');
+                }
+
+                if ($pid) {
+
+                    // Parent
+                    if (isset($this->_debug)) {
+                        echo $this->name() .
+                          " (parent) forked new child - pid $pid.\n";
+
+                    }
+
+                    $this->_children[] = $pid;
+
+                } else {
+
+                    // Child
+
+                    // Do something with each object
+                    $this->childTask($o);
+
+                    exit();
+                }
+
+                // Remove child from ps list as it finishes
+                while (($c = pcntl_wait($status, WNOHANG OR WUNTRACED)) > 0) {
+
+                    if (isset($this->_debug)) {
+                        echo $this->name() . " child $c finished.\n";
+                    }
+
+                    $this->removePs($this->_children, $c);
+                }
+
+                // Wait! We have too many damn kids.
+                if (sizeof($this->_children) >= $this->_max_children) {
+
+                    if (isset($this->_debug)) {
+                        echo $this->name() . " - Too many children. Waiting...\n";
+                    }
+
+                    if (($c = pcntl_wait($status, WUNTRACED)) > 0) {
+
+                        if (isset($this->_debug)) {
+                            echo $this->name() .
+                              " - Finished waiting for child $c.\n";
+                        }
+
+                        $this->removePs($this->_children, $c);
+                    }
+                }
+            }
+
+            // Remove all children from the process list before restarting
+            while (($c = pcntl_wait($status, WUNTRACED)) > 0) {
+
+                if (isset($this->_debug)) {
+                    echo $this->name() . " child $c finished.\n";
+                }
+
+                $this->removePs($this->_children, $c);
+            }
+
+            // Rest for a bit
+
+            if (isset($this->_debug)) {
+                echo $this->name() . ' - Waiting ' . $this->_interval .
+                  " secs before running again.\n";
+            }
+
+            if ($this->_interval > 0) {
+                sleep($this->_interval);
+            }
+
+        } while (true);
+    }
+
+    /**
+     * Remove a child process from the list of children
+     *
+     * @param array &$plist array of processes
+     * @param int   $ps     process id
+     *
+     * @return void
+     */
+
+    function removePs(&$plist, $ps)
+    {
+        for ($i = 0; $i < sizeof($plist); $i++) {
+            if ($plist[$i] == $ps) {
+                unset($plist[$i]);
+                $plist = array_values($plist);
+                break;
+            }
+        }
+    }
+
+    /**
+     * Get a list of objects to work on in parallel
+     *
+     * @return array An array of objects to work on
+     */
+
+    function getObjects()
+    {
+        die('Implement ParallelizingDaemon::getObjects().');
+    }
+
+    /**
+     * Do something with each object in parallel
+     *
+     * @param mixed $object data to work on
+     *
+     * @return void
+     */
+
+    function childTask($object)
+    {
+        die("Implement ParallelizingDaemon::childTask($object).");
+    }
+
+}
\ No newline at end of file