Merge pull request #3522 from annando/1706-lock

Some more poller speed and lock functionality

boot.php

@@ -35,12 +35,13 @@ require_once 'include/features.php';
 require_once 'include/identity.php';
 require_once 'update.php';
 require_once 'include/dbstructure.php';
+require_once 'include/poller.php';
 
 define ( 'FRIENDICA_PLATFORM',     'Friendica');
 define ( 'FRIENDICA_CODENAME',     'Asparagus');
 define ( 'FRIENDICA_VERSION',      '3.5.3-dev' );
 define ( 'DFRN_PROTOCOL_VERSION',  '2.23'    );
-define ( 'DB_UPDATE_VERSION',      1227      );
+define ( 'DB_UPDATE_VERSION',      1228      );
 
 /**
  * @brief Constant with a HTML line break.
@@ -1095,18 +1096,8 @@ function proc_run($cmd) {
 		return;
 	}
 
-	// Checking number of workers
-	$workers = q("SELECT COUNT(*) AS `workers` FROM `workerqueue` WHERE `executed` > '%s'", dbesc(NULL_DATE));
-
-	// Get number of allowed number of worker threads
-	$queues = intval(get_config("system", "worker_queues"));
-
-	if ($queues == 0) {
-		$queues = 4;
-	}
-
 	// If there are already enough workers running, don't fork another one
-	if ($workers[0]["workers"] >= $queues) {
+	if (poller_too_much_workers()) {
 		return;
 	}
 

database.sql

@@ -1,6 +1,6 @@
 -- ------------------------------------------
--- Friendica 3.5.2-rc (Asparagus)
+-- Friendica 3.5.3dev (Asparagus)
--- DB_UPDATE_VERSION 1227
+-- DB_UPDATE_VERSION 1228
 -- ------------------------------------------
 
 
@@ -580,7 +580,7 @@ CREATE TABLE IF NOT EXISTS `locks` (
 	`id` int(11) NOT NULL auto_increment,
 	`name` varchar(128) NOT NULL DEFAULT '',
 	`locked` tinyint(1) NOT NULL DEFAULT 0,
-	`created` datetime DEFAULT '0001-01-01 00:00:00',
+	`pid` int(10) unsigned NOT NULL DEFAULT 0,
 	 PRIMARY KEY(`id`)
 ) DEFAULT COLLATE utf8mb4_general_ci;
 
@@ -1116,6 +1116,7 @@ CREATE TABLE IF NOT EXISTS `workerqueue` (
 	`executed` datetime NOT NULL DEFAULT '0001-01-01 00:00:00',
 	 PRIMARY KEY(`id`),
 	 INDEX `pid` (`pid`),
+	 INDEX `parameter` (`parameter`(192)),
 	 INDEX `priority_created` (`priority`,`created`)
 ) DEFAULT COLLATE utf8mb4_general_ci;
 

doc/database/db_locks.md

@@ -2,10 +2,10 @@ Table locks
 ===========
 
 | Field   | Description      | Type             | Null | Key | Default             | Extra          |
-|---------|------------------|--------------|------|-----|---------------------|----------------|
+|---------|------------------|------------------|------|-----|---------------------|----------------|
 | id      | sequential ID    | int(11)          | NO   | PRI | NULL                | auto_increment |
 | name    |                  | varchar(128)     | NO   |     |                     |                |
 | locked  |                  | tinyint(1)       | NO   |     | 0                   |                |
-| created |                  | datetime     | YES  |     | 0001-01-01 00:00:00 |                |
+| pid     | Process ID       | int(10) unsigned | NO   |     | 0                   |                |
 
 Return to [database documentation](help/database)

include/cron.php

@@ -246,10 +246,11 @@ function cron_poll_contacts($argc, $argv) {
 			logger("Polling " . $contact["network"] . " " . $contact["id"] . " " . $contact["nick"] . " " . $contact["name"]);
 
 			if (($contact['network'] == NETWORK_FEED) AND ($contact['priority'] <= 3)) {
-				proc_run(PRIORITY_MEDIUM, 'include/onepoll.php', intval($contact['id']));
+				$priority = PRIORITY_MEDIUM;
 			} else {
-				proc_run(PRIORITY_LOW, 'include/onepoll.php', intval($contact['id']));
+				$priority = PRIORITY_LOW;
 			}
+			proc_run(array('priority' => $priority, 'dont_fork' => true), 'include/onepoll.php', intval($contact['id']));
 		}
 	}
 }

include/dba.php

@@ -806,6 +806,41 @@ class dba {
 		return self::e($sql, $param);
 	}
 
+	/**
+	 * @brief Locks a table for exclusive write access
+	 *
+	 * This function can be extended in the future to accept a table array as well.
+	 *
+	 * @param string $table Table name
+	 *
+	 * @return boolean was the lock successful?
+	 */
+	static public function lock($table) {
+		// See here: https://dev.mysql.com/doc/refman/5.7/en/lock-tables-and-transactions.html
+		self::e("SET autocommit=0");
+		$success = self::e("LOCK TABLES `".self::$dbo->escape($table)."` WRITE");
+		if (!$success) {
+			self::e("SET autocommit=1");
+		} else {
+			self::$in_transaction = true;
+		}
+		return $success;
+	}
+
+	/**
+	 * @brief Unlocks all locked tables
+	 *
+	 * @return boolean was the unlock successful?
+	 */
+	static public function unlock() {
+		// See here: https://dev.mysql.com/doc/refman/5.7/en/lock-tables-and-transactions.html
+		self::e("COMMIT");
+		$success = self::e("UNLOCK TABLES");
+		self::e("SET autocommit=1");
+		self::$in_transaction = false;
+		return $success;
+	}
+
 	/**
 	 * @brief Starts a transaction
 	 *

include/dbstructure.php

@@ -1205,7 +1205,7 @@ function db_definition() {
 					"id" => array("type" => "int(11)", "not null" => "1", "extra" => "auto_increment", "primary" => "1"),
 					"name" => array("type" => "varchar(128)", "not null" => "1", "default" => ""),
 					"locked" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
-					"created" => array("type" => "datetime", "default" => NULL_DATE),
+					"pid" => array("type" => "int(10) unsigned", "not null" => "1", "default" => "0"),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -1743,6 +1743,7 @@ function db_definition() {
 			"indexes" => array(
 					"PRIMARY" => array("id"),
 					"pid" => array("pid"),
+					"parameter" => array("parameter(192)"),
 					"priority_created" => array("priority", "created"),
 					)
 			);

include/lock.php

@@ -1,80 +0,0 @@
-<?php
-
-// Provide some ability to lock a PHP function so that multiple processes
-// can't run the function concurrently
-if (! function_exists('lock_function')) {
-function lock_function($fn_name, $block = true, $wait_sec = 2, $timeout = 30) {
-	if ( $wait_sec == 0 )
-		$wait_sec = 2;	// don't let the user pick a value that's likely to crash the system
-
-	$got_lock = false;
-	$start = time();
-
-	do {
-		q("LOCK TABLE `locks` WRITE");
-		$r = q("SELECT `locked`, `created` FROM `locks` WHERE `name` = '%s' LIMIT 1",
-			dbesc($fn_name)
-		);
-
-		if ((dbm::is_result($r)) AND (!$r[0]['locked'] OR (strtotime($r[0]['created']) < time() - 3600))) {
-			q("UPDATE `locks` SET `locked` = 1, `created` = '%s' WHERE `name` = '%s'",
-				dbesc(datetime_convert()),
-				dbesc($fn_name)
-			);
-			$got_lock = true;
-		}
-		elseif (! dbm::is_result($r)) {
-			/// @TODO the Boolean value for count($r) should be equivalent to the Boolean value of $r
-			q("INSERT INTO `locks` (`name`, `created`, `locked`) VALUES ('%s', '%s', 1)",
-				dbesc($fn_name),
-				dbesc(datetime_convert())
-			);
-			$got_lock = true;
-		}
-
-		q("UNLOCK TABLES");
-
-		if (($block) && (! $got_lock))
-			sleep($wait_sec);
-
-	} while (($block) && (! $got_lock) && ((time() - $start) < $timeout));
-
-	logger('lock_function: function ' . $fn_name . ' with blocking = ' . $block . ' got_lock = ' . $got_lock . ' time = ' . (time() - $start), LOGGER_DEBUG);
-
-	return $got_lock;
-}}
-
-
-if (! function_exists('block_on_function_lock')) {
-function block_on_function_lock($fn_name, $wait_sec = 2, $timeout = 30) {
-	if ( $wait_sec == 0 )
-		$wait_sec = 2;	// don't let the user pick a value that's likely to crash the system
-
-	$start = time();
-
-	do {
-		$r = q("SELECT locked FROM locks WHERE name = '%s' LIMIT 1",
-			dbesc($fn_name)
-		);
-
-		if (dbm::is_result($r) && $r[0]['locked']) {
-			sleep($wait_sec);
-		}
-
-	} while (dbm::is_result($r) && $r[0]['locked'] && ((time() - $start) < $timeout));
-
-	return;
-}}
-
-
-if (! function_exists('unlock_function')) {
-function unlock_function($fn_name) {
-	$r = q("UPDATE `locks` SET `locked` = 0, `created` = '%s' WHERE `name` = '%s'",
-			dbesc(NULL_DATE),
-			dbesc($fn_name)
-	     );
-
-	logger('unlock_function: released lock for function ' . $fn_name, LOGGER_DEBUG);
-
-	return;
-}}

include/notifier.php

@@ -498,7 +498,7 @@ function notifier_run(&$argv, &$argc){
 			}
 			logger("Deliver ".$target_item["guid"]." to ".$contact['url']." via network ".$contact['network'], LOGGER_DEBUG);
 
-			proc_run($priority, 'include/delivery.php', $cmd, $item_id, $contact['id']);
+			proc_run(array('priority' => $priority, 'dont_fork' => true), 'include/delivery.php', $cmd, $item_id, $contact['id']);
 		}
 	}
 
@@ -563,7 +563,7 @@ function notifier_run(&$argv, &$argc){
 
 				if ((! $mail) && (! $fsuggest) && (! $followup)) {
 					logger('notifier: delivery agent: '.$rr['name'].' '.$rr['id'].' '.$rr['network'].' '.$target_item["guid"]);
-					proc_run($priority, 'include/delivery.php', $cmd, $item_id, $rr['id']);
+					proc_run(array('priority' => $priority, 'dont_fork' => true), 'include/delivery.php', $cmd, $item_id, $rr['id']);
 				}
 			}
 		}
@@ -603,7 +603,7 @@ function notifier_run(&$argv, &$argc){
 		}
 
 		// Handling the pubsubhubbub requests
-		proc_run(PRIORITY_HIGH, 'include/pubsubpublish.php');
+		proc_run(array('priority' => PRIORITY_HIGH, 'dont_fork' => true), 'include/pubsubpublish.php');
 	}
 
 	logger('notifier: calling hooks', LOGGER_DEBUG);

include/poller.php

@@ -2,13 +2,14 @@
 
 use Friendica\App;
 use Friendica\Core\Config;
+use Friendica\Util\Lock;
 
 if (!file_exists("boot.php") AND (sizeof($_SERVER["argv"]) != 0)) {
 	$directory = dirname($_SERVER["argv"][0]);
 
-	if (substr($directory, 0, 1) != "/")
+	if (substr($directory, 0, 1) != "/") {
 		$directory = $_SERVER["PWD"]."/".$directory;
-
+	}
 	$directory = realpath($directory."/..");
 
 	chdir($directory);
@@ -19,16 +20,12 @@ require_once("boot.php");
 function poller_run($argv, $argc){
 	global $a, $db;
 
-	if (is_null($a)) {
 	$a = new App(dirname(__DIR__));
-	}
 
-	if (is_null($db)) {
 	@include(".htconfig.php");
 	require_once("include/dba.php");
 	$db = new dba($db_host, $db_user, $db_pass, $db_data);
 	unset($db_host, $db_user, $db_pass, $db_data);
-	};
 
 	Config::load();
 
@@ -41,54 +38,74 @@ function poller_run($argv, $argc){
 
 	load_hooks();
 
+	// At first check the maximum load. We shouldn't continue with a high load
+	if ($a->maxload_reached()) {
+		logger('Pre check: maximum load reached, quitting.', LOGGER_DEBUG);
+		return;
+	}
+
+	// We now start the process. This is done after the load check since this could increase the load.
 	$a->start_process();
 
+	// At first we check the number of workers and quit if there are too much of them
+	// This is done at the top to avoid that too much code is executed without a need to do so,
+	// since the poller mostly quits here.
+	if (poller_too_much_workers()) {
+		poller_kill_stale_workers();
+		logger('Pre check: Active worker limit reached, quitting.', LOGGER_DEBUG);
+		return;
+	}
+
+	// Do we have too few memory?
 	if ($a->min_memory_reached()) {
+		logger('Pre check: Memory limit reached, quitting.', LOGGER_DEBUG);
 		return;
 	}
 
+	// Possibly there are too much database connections
 	if (poller_max_connections_reached()) {
+		logger('Pre check: maximum connections reached, quitting.', LOGGER_DEBUG);
 		return;
 	}
 
-	if ($a->maxload_reached()) {
+	// Possibly there are too much database processes that block the system
+	if ($a->max_processes_reached()) {
+		logger('Pre check: maximum processes reached, quitting.', LOGGER_DEBUG);
 		return;
 	}
 
+	// Now we start additional cron processes if we should do so
 	if (($argc <= 1) OR ($argv[1] != "no_cron")) {
 		poller_run_cron();
 	}
 
-	if ($a->max_processes_reached()) {
-		return;
-	}
-
-	// Checking the number of workers
-	if (poller_too_much_workers()) {
-		poller_kill_stale_workers();
-		return;
-	}
-
 	$starttime = time();
 
+	// We fetch the next queue entry that is about to be executed
 	while ($r = poller_worker_process()) {
 
+		// If we got that queue entry we claim it for us
 		if (!poller_claim_process($r[0])) {
 			continue;
 		}
 
+		// To avoid the quitting of multiple pollers only one poller at a time will execute the check
+		if (Lock::set('poller_worker', 0)) {
+			// Count active workers and compare them with a maximum value that depends on the load
+			if (poller_too_much_workers()) {
+				logger('Active worker limit reached, quitting.', LOGGER_DEBUG);
+				return;
+			}
+
 			// Check free memory
 			if ($a->min_memory_reached()) {
 				logger('Memory limit reached, quitting.', LOGGER_DEBUG);
 				return;
 			}
-
+			Lock::remove('poller_worker');
-		// Count active workers and compare them with a maximum value that depends on the load
-		if (poller_too_much_workers()) {
-			logger('Active worker limit reached, quitting.', LOGGER_DEBUG);
-			return;
 		}
 
+		// finally the work will be done
 		if (!poller_execute($r[0])) {
 			logger('Process execution failed, quitting.', LOGGER_DEBUG);
 			return;
@@ -96,7 +113,7 @@ function poller_run($argv, $argc){
 
 		// Quit the poller once every hour
 		if (time() > ($starttime + 3600)) {
-			logger('Process lifetime reachted, quitting.', LOGGER_DEBUG);
+			logger('Process lifetime reached, quitting.', LOGGER_DEBUG);
 			return;
 		}
 	}
@@ -150,7 +167,6 @@ function poller_execute($queue) {
 	$funcname = str_replace(".php", "", basename($argv[0]))."_run";
 
 	if (function_exists($funcname)) {
-
 		poller_exec_function($queue, $funcname, $argv);
 		dba::delete('workerqueue', array('id' => $queue["id"]));
 	} else {
@@ -226,26 +242,29 @@ function poller_exec_function($queue, $funcname, $argv) {
 				$o = "\nDatabase Read:\n";
 				foreach ($a->callstack["database"] AS $func => $time) {
 					$time = round($time, 3);
-					if ($time > 0)
+					if ($time > 0) {
 						$o .= $func.": ".$time."\n";
 					}
 				}
+			}
 			if (isset($a->callstack["database_write"])) {
 				$o .= "\nDatabase Write:\n";
 				foreach ($a->callstack["database_write"] AS $func => $time) {
 					$time = round($time, 3);
-					if ($time > 0)
+					if ($time > 0) {
 						$o .= $func.": ".$time."\n";
 					}
 				}
+			}
 			if (isset($a->callstack["network"])) {
 				$o .= "\nNetwork:\n";
 				foreach ($a->callstack["network"] AS $func => $time) {
 					$time = round($time, 3);
-					if ($time > 0)
+					if ($time > 0) {
 						$o .= $func.": ".$time."\n";
 					}
 				}
+			}
 		} else {
 			$o = '';
 		}
@@ -284,27 +303,30 @@ function poller_max_connections_reached() {
 	if ($max == 0) {
 		// the maximum number of possible user connections can be a system variable
 		$r = q("SHOW VARIABLES WHERE `variable_name` = 'max_user_connections'");
-		if ($r)
+		if (dbm::is_result($r)) {
 			$max = $r[0]["Value"];
-
+		}
 		// Or it can be granted. This overrides the system variable
 		$r = q("SHOW GRANTS");
-		if ($r)
+		if (dbm::is_result($r)) {
 			foreach ($r AS $grants) {
 				$grant = array_pop($grants);
-				if (stristr($grant, "GRANT USAGE ON"))
+				if (stristr($grant, "GRANT USAGE ON")) {
-					if (preg_match("/WITH MAX_USER_CONNECTIONS (\d*)/", $grant, $match))
+					if (preg_match("/WITH MAX_USER_CONNECTIONS (\d*)/", $grant, $match)) {
 						$max = $match[1];
 					}
 				}
+			}
+		}
+	}
 
 	// If $max is set we will use the processlist to determine the current number of connections
 	// The processlist only shows entries of the current user
 	if ($max != 0) {
 		$r = q("SHOW PROCESSLIST");
-		if (!dbm::is_result($r))
+		if (!dbm::is_result($r)) {
 			return false;
-
+		}
 		$used = count($r);
 
 		logger("Connection usage (user values): ".$used."/".$max, LOGGER_DEBUG);
@@ -320,28 +342,28 @@ function poller_max_connections_reached() {
 	// We will now check for the system values.
 	// This limit could be reached although the user limits are fine.
 	$r = q("SHOW VARIABLES WHERE `variable_name` = 'max_connections'");
-	if (!$r)
+	if (!dbm::is_result($r)) {
 		return false;
-
+	}
 	$max = intval($r[0]["Value"]);
-	if ($max == 0)
+	if ($max == 0) {
 		return false;
-
+	}
 	$r = q("SHOW STATUS WHERE `variable_name` = 'Threads_connected'");
-	if (!$r)
+	if (!dbm::is_result($r)) {
 		return false;
-
+	}
 	$used = intval($r[0]["Value"]);
-	if ($used == 0)
+	if ($used == 0) {
 		return false;
-
+	}
 	logger("Connection usage (system values): ".$used."/".$max, LOGGER_DEBUG);
 
 	$level = $used / $max * 100;
 
-	if ($level < $maxlevel)
+	if ($level < $maxlevel) {
 		return false;
-
+	}
 	logger("Maximum level (".$level."%) of system connections reached: ".$used."/".$max);
 	return true;
 }
@@ -440,8 +462,7 @@ function poller_too_much_workers() {
 			dba::close($processes);
 		}
 		dba::close($entries);
-
+		$processlist = ' ('.implode(', ', $listitem).')';
-		$processlist = implode(', ', $listitem);
 
 		$s = q("SELECT COUNT(*) AS `total` FROM `workerqueue` WHERE `executed` <= '%s'", dbesc(NULL_DATE));
 		$entries = $s[0]["total"];
@@ -460,7 +481,7 @@ function poller_too_much_workers() {
 			}
 		}
 
-		logger("Load: ".$load."/".$maxsysload." - processes: ".$active."/".$entries." (".$processlist.") - maximum: ".$queues."/".$maxqueues, LOGGER_DEBUG);
+		logger("Load: ".$load."/".$maxsysload." - processes: ".$active."/".$entries.$processlist." - maximum: ".$queues."/".$maxqueues, LOGGER_DEBUG);
 
 		// Are there fewer workers running as possible? Then fork a new one.
 		if (!Config::get("system", "worker_dont_fork") AND ($queues > ($active + 1)) AND ($entries > 1)) {
@@ -471,7 +492,7 @@ function poller_too_much_workers() {
 		}
 	}
 
-	return($active >= $queues);
+	return $active >= $queues;
 }
 
 /**
@@ -482,7 +503,7 @@ function poller_too_much_workers() {
 function poller_active_workers() {
 	$workers = q("SELECT COUNT(*) AS `processes` FROM `process` WHERE `command` = 'poller.php'");
 
-	return($workers[0]["processes"]);
+	return $workers[0]["processes"];
 }
 
 /**
@@ -503,36 +524,37 @@ function poller_passing_slow(&$highest_priority) {
 		INNER JOIN `workerqueue` ON `workerqueue`.`pid` = `process`.`pid`");
 
 	// No active processes at all? Fine
-	if (!dbm::is_result($r))
+	if (!dbm::is_result($r)) {
-		return(false);
+		return false;
-
+	}
 	$priorities = array();
-	foreach ($r AS $line)
+	foreach ($r AS $line) {
 		$priorities[] = $line["priority"];
-
+	}
 	// Should not happen
-	if (count($priorities) == 0)
+	if (count($priorities) == 0) {
-		return(false);
+		return false;
-
+	}
 	$highest_priority = min($priorities);
 
 	// The highest process is already the slowest one?
 	// Then we quit
-	if ($highest_priority == PRIORITY_NEGLIGIBLE)
+	if ($highest_priority == PRIORITY_NEGLIGIBLE) {
-		return(false);
+		return false;
-
+	}
 	$high = 0;
-	foreach ($priorities AS $priority)
+	foreach ($priorities AS $priority) {
-		if ($priority == $highest_priority)
+		if ($priority == $highest_priority) {
 			++$high;
-
+		}
+	}
 	logger("Highest priority: ".$highest_priority." Total processes: ".count($priorities)." Count high priority processes: ".$high, LOGGER_DEBUG);
 	$passing_slow = (($high/count($priorities)) > (2/3));
 
-	if ($passing_slow)
+	if ($passing_slow) {
 		logger("Passing slower processes than priority ".$highest_priority, LOGGER_DEBUG);
-
+	}
-	return($passing_slow);
+	return $passing_slow;
 }
 
 /**
@@ -546,7 +568,7 @@ function poller_worker_process() {
 	$highest_priority = 0;
 
 	if (poller_passing_slow($highest_priority)) {
-		dba::e('LOCK TABLES `workerqueue` WRITE');
+		dba::lock('workerqueue');
 
 		// Are there waiting processes with a higher priority than the currently highest?
 		$r = q("SELECT * FROM `workerqueue`
@@ -568,7 +590,7 @@ function poller_worker_process() {
 			return $r;
 		}
 	} else {
-		dba::e('LOCK TABLES `workerqueue` WRITE');
+		dba::lock('workerqueue');
 	}
 
 	// If there is no result (or we shouldn't pass lower processes) we check without priority limit
@@ -578,7 +600,7 @@ function poller_worker_process() {
 
 	// We only unlock the tables here, when we got no data
 	if (!dbm::is_result($r)) {
-		dba::e('UNLOCK TABLES');
+		dba::unlock();
 	}
 
 	return $r;
@@ -598,7 +620,7 @@ function poller_claim_process($queue) {
 
 	$success = dba::update('workerqueue', array('executed' => datetime_convert(), 'pid' => $mypid),
 			array('id' => $queue["id"], 'pid' => 0));
-	dba::e('UNLOCK TABLES');
+	dba::unlock();
 
 	if (!$success) {
 		logger("Couldn't update queue entry ".$queue["id"]." - skip this execution", LOGGER_DEBUG);
@@ -729,5 +751,7 @@ if (array_search(__file__,get_included_files())===0){
 
 	get_app()->end_process();
 
+	Lock::remove('poller_worker');
+
 	killme();
 }

include/pubsubpublish.php

@@ -17,7 +17,7 @@ function pubsubpublish_run(&$argv, &$argc){
 
 		foreach ($r as $rr) {
 			logger("Publish feed to ".$rr["callback_url"], LOGGER_DEBUG);
-			proc_run(PRIORITY_HIGH, 'include/pubsubpublish.php', $rr["id"]);
+			proc_run(array('priority' => PRIORITY_HIGH, 'dont_fork' => true), 'include/pubsubpublish.php', $rr["id"]);
 		}
 	}
 

include/queue.php

@@ -27,7 +27,7 @@ function queue_run(&$argv, &$argc){
 		logger('queue: start');
 
 		// Handling the pubsubhubbub requests
-		proc_run(PRIORITY_HIGH,'include/pubsubpublish.php');
+		proc_run(array('priority' => PRIORITY_HIGH, 'dont_fork' => true), 'include/pubsubpublish.php');
 
 		$r = q("SELECT `queue`.*, `contact`.`name`, `contact`.`uid` FROM `queue`
 			INNER JOIN `contact` ON `queue`.`cid` = `contact`.`id`
@@ -51,7 +51,7 @@ function queue_run(&$argv, &$argc){
 		if (dbm::is_result($r)) {
 			foreach ($r as $q_item) {
 				logger('Call queue for id '.$q_item['id']);
-				proc_run(PRIORITY_LOW, "include/queue.php", $q_item['id']);
+				proc_run(array('priority' => PRIORITY_LOW, 'dont_fork' => true), "include/queue.php", $q_item['id']);
 			}
 		}
 		return;

include/socgraph.php

@@ -1995,10 +1995,11 @@ function get_gcontact_id($contact) {
 	if (in_array($contact["network"], array(NETWORK_DFRN, NETWORK_DIASPORA, NETWORK_OSTATUS)))
 		$contact["url"] = clean_contact_url($contact["url"]);
 
-	$r = q("SELECT `id`, `last_contact`, `last_failure`, `network` FROM `gcontact` WHERE `nurl` = '%s' LIMIT 2",
+	dba::lock('gcontact');
+	$r = q("SELECT `id`, `last_contact`, `last_failure`, `network` FROM `gcontact` WHERE `nurl` = '%s' LIMIT 1",
 		dbesc(normalise_link($contact["url"])));
 
-	if ($r) {
+	if (dbm::is_result($r)) {
 		$gcontact_id = $r[0]["id"];
 
 		// Update every 90 days
@@ -2036,17 +2037,13 @@ function get_gcontact_id($contact) {
 			$doprobing = in_array($r[0]["network"], array(NETWORK_DFRN, NETWORK_DIASPORA, NETWORK_OSTATUS, ""));
 		}
 	}
+	dba::unlock();
 
 	if ($doprobing) {
 		logger("Last Contact: ". $last_contact_str." - Last Failure: ".$last_failure_str." - Checking: ".$contact["url"], LOGGER_DEBUG);
 		proc_run(PRIORITY_LOW, 'include/gprobe.php', bin2hex($contact["url"]));
 	}
 
-	if ((dbm::is_result($r)) AND (count($r) > 1) AND ($gcontact_id > 0) AND ($contact["url"] != ""))
-	 q("DELETE FROM `gcontact` WHERE `nurl` = '%s' AND `id` != %d",
-		dbesc(normalise_link($contact["url"])),
-		intval($gcontact_id));
-
 	return $gcontact_id;
 }
 

src/App.php

@@ -797,6 +797,8 @@ class App {
 	 * @return bool Is the limit reached?
 	 */
 	function max_processes_reached() {
+		// Deactivated, needs more investigating if this check really makes sense
+		return false;
 
 		if ($this->is_backend()) {
 			$process = 'backend';

src/Util/Lock.php

@@ -0,0 +1,159 @@
+<?php
+
+namespace Friendica\Util;
+
+/**
+ * @file src/Util/Lock.php
+ * @brief Functions for preventing parallel execution of functions
+ *
+ */
+
+use Friendica\Core\Config;
+use Memcache;
+use dba;
+use dbm;
+
+/**
+ * @brief This class contain Functions for preventing parallel execution of functions
+ */
+class Lock {
+       /**
+	 * @brief Check for memcache and open a connection if configured
+	 *
+	 * @return object|boolean The memcache object - or "false" if not successful
+	 */
+	private static function connectMemcache() {
+		if (!function_exists('memcache_connect')) {
+			return false;
+		}
+
+		if (!Config::get('system', 'memcache')) {
+			return false;
+		}
+
+		$memcache_host = Config::get('system', 'memcache_host', '127.0.0.1');
+		$memcache_port = Config::get('system', 'memcache_port', 11211);
+
+		$memcache = new Memcache;
+
+		if (!$memcache->connect($memcache_host, $memcache_port)) {
+			return false;
+		}
+
+		return $memcache;
+	}
+
+	/**
+	 * @brief Sets a lock for a given name
+	 *
+	 * @param string $fn_name Name of the lock
+	 * @param integer $timeout Seconds until we give up
+	 *
+	 * @return boolean Was the lock successful?
+	 */
+	public static function set($fn_name, $timeout = 120) {
+		$got_lock = false;
+		$start = time();
+
+		$memcache = self::connectMemcache();
+		if (is_object($memcache)) {
+			$wait_sec = 0.2;
+			$cachekey = get_app()->get_hostname().";lock:".$fn_name;
+
+			do {
+				$lock = $memcache->get($cachekey);
+
+				if (!is_bool($lock)) {
+					$pid = (int)$lock;
+
+					// When the process id isn't used anymore, we can safely claim the lock for us.
+					// Or we do want to lock something that was already locked by us.
+					if (!posix_kill($pid, 0) OR ($pid == getmypid())) {
+						$lock = false;
+					}
+				}
+				if (is_bool($lock)) {
+					$memcache->set($cachekey, getmypid(), MEMCACHE_COMPRESSED, 300);
+					$got_lock = true;
+				}
+				if (!$got_lock AND ($timeout > 0)) {
+					usleep($wait_sec * 1000000);
+				}
+			} while (!$got_lock AND ((time() - $start) < $timeout));
+
+			return $got_lock;
+		}
+
+		$wait_sec = 2;
+
+		do {
+			dba::lock('locks');
+			$lock = dba::select('locks', array('locked', 'pid'), array('name' => $fn_name), array('limit' => 1));
+
+			if (dbm::is_result($lock)) {
+				if ($lock['locked']) {
+					// When the process id isn't used anymore, we can safely claim the lock for us.
+					if (!posix_kill($lock['pid'], 0)) {
+						$lock['locked'] = false;
+					}
+					// We want to lock something that was already locked by us? So we got the lock.
+					if ($lock['pid'] == getmypid()) {
+						$got_lock = true;
+					}
+				}
+				if (!$lock['locked']) {
+					dba::update('locks', array('locked' => true, 'pid' => getmypid()), array('name' => $fn_name));
+					$got_lock = true;
+				}
+			} elseif (!dbm::is_result($lock)) {
+				dba::insert('locks', array('name' => $fn_name, 'locked' => true, 'pid' => getmypid()));
+				$got_lock = true;
+			}
+
+			dba::unlock();
+
+			if (!$got_lock AND ($timeout > 0)) {
+				sleep($wait_sec);
+			}
+		} while (!$got_lock AND ((time() - $start) < $timeout));
+
+		return $got_lock;
+	}
+
+	/**
+	 * @brief Removes a lock if it was set by us
+	 *
+	 * @param string $fn_name Name of the lock
+	 */
+	public static function remove($fn_name) {
+		$memcache = self::connectMemcache();
+		if (is_object($memcache)) {
+			$cachekey = get_app()->get_hostname().";lock:".$fn_name;
+			$lock = $memcache->get($cachekey);
+
+			if (!is_bool($lock)) {
+				if ((int)$lock == getmypid()) {
+					$memcache->delete($cachekey);
+				}
+			}
+			return;
+		}
+
+		dba::update('locks', array('locked' => false, 'pid' => 0), array('name' => $fn_name, 'pid' => getmypid()));
+		return;
+	}
+
+	/**
+	 * @brief Removes all lock that were set by us
+	 */
+	public static function removeAll() {
+		$memcache = self::connectMemcache();
+		if (is_object($memcache)) {
+			// We cannot delete all cache entries, but this doesn't matter with memcache
+			return;
+		}
+
+		dba::update('locks', array('locked' => false, 'pid' => 0), array('pid' => getmypid()));
+		return;
+	}
+}

update.php

@@ -1,6 +1,6 @@
 <?php
 
-define('UPDATE_VERSION' , 1227);
+define('UPDATE_VERSION' , 1228);
 
 /**
  *