+/**
+ * @brief Checks if the number of database connections has reached a critical limit.
+ *
+ * @return bool Are more than 3/4 of the maximum connections used?
+ */
+function poller_max_connections_reached() {
+
+ // Fetch the max value from the config. This is needed when the system cannot detect the correct value by itself.
+ $max = get_config("system", "max_connections");
+
+ if ($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)
+ $max = $r[0]["Value"];
+
+ // Or it can be granted. This overrides the system variable
+ $r = q("SHOW GRANTS");
+ if ($r)
+ foreach ($r AS $grants) {
+ $grant = array_pop($grants);
+ if (stristr($grant, "GRANT USAGE ON"))
+ 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) {
+ $r = q("SHOW PROCESSLIST");
+ if (!$r)
+ return false;
+
+ $used = count($r);
+
+ logger("Connection usage (user values): ".$used."/".$max, LOGGER_DEBUG);
+
+ $level = $used / $max;
+
+ if ($level >= (3/4)) {
+ logger("Maximum level (3/4) of user connections reached: ".$used."/".$max);
+ return true;
+ }
+ }
+
+ // 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)
+ return false;
+
+ $max = intval($r[0]["Value"]);
+ if ($max == 0)
+ return false;
+
+ $r = q("SHOW STATUS WHERE `variable_name` = 'Threads_connected'");
+ if (!$r)
+ return false;
+
+ $used = intval($r[0]["Value"]);
+ if ($used == 0)
+ return false;
+
+ logger("Connection usage (system values): ".$used."/".$max, LOGGER_DEBUG);
+
+ $level = $used / $max;
+
+ if ($level < (3/4))
+ return false;
+
+ logger("Maximum level (3/4) of system connections reached: ".$used."/".$max);
+ return true;
+}
+
+/**
+ * @brief fix the queue entry if the worker process died
+ *
+ */
+function poller_kill_stale_workers() {
+ $r = q("SELECT `pid`, `executed` FROM `workerqueue` WHERE `executed` != '0000-00-00 00:00:00'");
+
+ if (!is_array($r) || count($r) == 0) {
+ // No processing here needed
+ return;
+ }
+
+ foreach($r AS $pid)
+ if (!posix_kill($pid["pid"], 0))
+ q("UPDATE `workerqueue` SET `executed` = '0000-00-00 00:00:00', `pid` = 0 WHERE `pid` = %d",
+ intval($pid["pid"]));
+ else {
+ // Kill long running processes
+ $duration = (time() - strtotime($pid["executed"])) / 60;
+ if ($duration > 180) {
+ logger("Worker process ".$pid["pid"]." took more than 3 hours. It will be killed now.");
+ posix_kill($pid["pid"], SIGTERM);
+
+ // Question: If a process is stale: Should we remove it or should we reschedule it?
+ // By now we rescheduling it. It's maybe not the wisest decision?
+ q("UPDATE `workerqueue` SET `executed` = '0000-00-00 00:00:00', `pid` = 0 WHERE `pid` = %d",
+ intval($pid["pid"]));
+ } else
+ logger("Worker process ".$pid["pid"]." now runs for ".round($duration)." minutes. That's okay.", LOGGER_DEBUG);
+ }
+}
+