Bugfix: The poller often couldn't store the pid in the workerqueue

diff --git a/include/poller.php b/include/poller.php
index 839e5c11bbdb36c9f027d57542fa19b269bb474d..0c5bebbda57f911de9e82da7ff326cd28dc372b2 100644 (file)
--- a/include/poller.php
+++ b/include/poller.php
@@ -73,6 +73,10 @@ function poller_run($argv, $argc){
 
        while ($r = poller_worker_process()) {
 
+               if (!poller_claim_process($r[0])) {
+                       continue;
+               }
+
                // Check free memory
                if ($a->min_memory_reached()) {
                        return;
@@ -108,43 +112,22 @@ function poller_execute($queue) {
 
        // Quit when in maintenance
        if (Config::get('system', 'maintenance', true)) {
+               logger("Maintenance mode - quit process ".$mypid, LOGGER_DEBUG);
                return false;
        }
 
        // Constantly check the number of parallel database processes
        if ($a->max_processes_reached()) {
+               logger("Max processes reached for process ".$mypid, LOGGER_DEBUG);
                return false;
        }
 
        // Constantly check the number of available database connections to let the frontend be accessible at any time
        if (poller_max_connections_reached()) {
+               logger("Max connection reached for process ".$mypid, LOGGER_DEBUG);
                return false;
        }
 
-       if (!dba::update('workerqueue', array('executed' => datetime_convert(), 'pid' => $mypid),
-                       array('id' => $queue["id"], 'pid' => 0))) {
-               logger("Couldn't update queue entry ".$queue["id"]." - skip this execution", LOGGER_DEBUG);
-               dba::commit();
-               return true;
-       }
-
-       // Assure that there are no tasks executed twice
-       $id = q("SELECT `pid`, `executed` FROM `workerqueue` WHERE `id` = %d", intval($queue["id"]));
-       if (!$id) {
-               logger("Queue item ".$queue["id"]." vanished - skip this execution", LOGGER_DEBUG);
-               dba::commit();
-               return true;
-       } elseif ((strtotime($id[0]["executed"]) <= 0) OR ($id[0]["pid"] == 0)) {
-               logger("Entry for queue item ".$queue["id"]." wasn't stored - skip this execution", LOGGER_DEBUG);
-               dba::commit();
-               return true;
-       } elseif ($id[0]["pid"] != $mypid) {
-               logger("Queue item ".$queue["id"]." is to be executed by process ".$id[0]["pid"]." and not by me (".$mypid.") - skip this execution", LOGGER_DEBUG);
-               dba::commit();
-               return true;
-       }
-       dba::commit();
-
        $argv = json_decode($queue["parameter"]);
 
        // Check for existance and validity of the include file
@@ -566,7 +549,7 @@ function poller_worker_process() {
                // Are there waiting processes with a higher priority than the currently highest?
                $r = q("SELECT * FROM `workerqueue`
                                WHERE `executed` <= '%s' AND `priority` < %d
-                               ORDER BY `priority`, `created` LIMIT 1",
+                               ORDER BY `priority`, `created` LIMIT 1 FOR UPDATE",
                                dbesc(NULL_DATE),
                                intval($highest_priority));
                if (dbm::is_result($r)) {
@@ -575,18 +558,70 @@ function poller_worker_process() {
                // Give slower processes some processing time
                $r = q("SELECT * FROM `workerqueue`
                                WHERE `executed` <= '%s' AND `priority` > %d
-                               ORDER BY `priority`, `created` LIMIT 1",
+                               ORDER BY `priority`, `created` LIMIT 1 FOR UPDATE",
                                dbesc(NULL_DATE),
                                intval($highest_priority));
+
+               if (dbm::is_result($r)) {
+                       return $r;
+               }
        }
 
        // If there is no result (or we shouldn't pass lower processes) we check without priority limit
-       if (($highest_priority == 0) OR !dbm::is_result($r)) {
-               $r = q("SELECT * FROM `workerqueue` WHERE `executed` <= '%s' ORDER BY `priority`, `created` LIMIT 1", dbesc(NULL_DATE));
+       if (!dbm::is_result($r)) {
+               $r = q("SELECT * FROM `workerqueue` WHERE `executed` <= '%s' ORDER BY `priority`, `created` LIMIT 1 FOR UPDATE", dbesc(NULL_DATE));
        }
+
        return $r;
 }
 
+/**
+ * @brief Assigns a workerqueue entry to the current process
+ *
+ * All the checks after the update are only needed with MyISAM.
+ *
+ * @param array $queue Workerqueue entry
+ *
+ * @return boolean "true" if the claiming was successful
+ */
+function poller_claim_process($queue) {
+       $mypid = getmypid();
+
+       if (!dba::update('workerqueue', array('executed' => datetime_convert(), 'pid' => $mypid),
+                       array('id' => $queue["id"], 'pid' => 0))) {
+               logger("Couldn't update queue entry ".$queue["id"]." - skip this execution", LOGGER_DEBUG);
+               dba::commit();
+               return false;
+       }
+
+       // Assure that there are no tasks executed twice
+       $id = q("SELECT `pid`, `executed` FROM `workerqueue` WHERE `id` = %d", intval($queue["id"]));
+       if (!$id) {
+               logger("Queue item ".$queue["id"]." vanished - skip this execution", LOGGER_DEBUG);
+               dba::commit();
+               return false;
+       } elseif ((strtotime($id[0]["executed"]) <= 0) OR ($id[0]["pid"] == 0)) {
+               logger("Entry for queue item ".$queue["id"]." wasn't stored - skip this execution", LOGGER_DEBUG);
+               dba::commit();
+               return false;
+       } elseif ($id[0]["pid"] != $mypid) {
+               logger("Queue item ".$queue["id"]." is to be executed by process ".$id[0]["pid"]." and not by me (".$mypid.") - skip this execution", LOGGER_DEBUG);
+               dba::commit();
+               return false;
+       }
+       dba::commit();
+       return true;
+}
+
+/**
+ * @brief Removes a workerqueue entry from the current process
+ */
+function poller_unclaim_process() {
+       $mypid = getmypid();
+
+       dba::update('workerqueue', array('executed' => NULL_DATE, 'pid' => 0), array('pid' => $mypid));
+}
+
 /**
  * @brief Call the front end worker
  */
@@ -683,6 +718,8 @@ function poller_run_cron() {
 if (array_search(__file__,get_included_files())===0){
        poller_run($_SERVER["argv"],$_SERVER["argc"]);
 
+       poller_unclaim_process();
+
        get_app()->end_process();
 
        killme();

diff --git a/mod/worker.php b/mod/worker.php
index 62f9bd3dde232d8611a150101b41a78adccd1e0c..947656ab7c2eebd4bab04384b906c939544ede6d 100644 (file)
--- a/mod/worker.php
+++ b/mod/worker.php
@@ -41,11 +41,15 @@ function worker_init($a){
                // But since it doesn't destroy anything, we just try to get more execution time in any way.
                set_time_limit(0);
 
-               poller_execute($r[0]);
+               if (poller_claim_process($r[0])) {
+                       poller_execute($r[0]);
+               }
        }
 
        call_worker();
 
+       poller_unclaim_process();
+
        $a->end_process();
 
        logger("Front end worker ended: ".getmypid());