while ($r = q("SELECT * FROM `workerqueue` WHERE `executed` = '0000-00-00 00:00:00' ORDER BY `created` LIMIT 1")) {
+ // Constantly check the number of available database connections to let the frontend be accessible at any time
+ if (poller_max_connections_reached())
+ return;
+
// Count active workers and compare them with a maximum value that depends on the load
if (poller_too_much_workers(3))
return;
* @return bool Are more than 3/4 of the maximum connections used?
*/
function poller_max_connections_reached() {
- $r = q("SHOW VARIABLES WHERE `variable_name` = 'max_connections'");
- if (!$r)
- return false;
// 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) {
- $max = intval($r[0]["Value"]);
- 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;
- $connected = intval($r[0]["Value"]);
- if ($connected == 0)
+ $used = intval($r[0]["Value"]);
+ if ($used == 0)
return false;
- $level = $connected / $max;
+ logger("Connection usage (system values): ".$used."/".$max, LOGGER_DEBUG);
- logger("Connection usage: ".$connected."/".$max, LOGGER_DEBUG);
+ $level = $used / $max;
if ($level < (3/4))
return false;
- logger("Maximum level (3/4) of connections reached: ".$connected."/".$max);
+ logger("Maximum level (3/4) of system connections reached: ".$used."/".$max);
return true;
-
}
/**