Default Parameters for MySQLDeadLckTest

A deadlock is a situation where different transactions are unable to proceed because each holds a lock that the other needs. Because both transactions are waiting for a resource to become available, neither ever release the locks it holds. A deadlock can occur when transactions lock rows in multiple tables (through statements such as UPDATE or SELECT ... FOR UPDATE), but in the opposite order. A deadlock can also occur when such statements lock ranges of index records and gaps, with each transaction acquiring some locks but not others due to a timing issue. When deadlock detection is enabled (the default) and a deadlock does occur, InnoDB (the default MySQL Storage engine) detects the condition and rolls back one of the transactions.

If deadlock detection is disabled, InnoDB relies on the innodb_lock_wait_timeout setting to roll back transactions in case of a deadlock. Though the transactions can be rolled back after the time specified against the innodb_lock_wait_timeout setting, administrators have to patiently wait for the roll back to happen. To avoid such wait time, administrators need to constantly keep a vigil on whether the deadlock detection is enabled or not. The MySQLDeadLckTest test helps administrators in this regard!

This test reports whether/not the deadlock detection is enabled and reports the count of deadlocks that occurred on the target MySQL database server.

This page depicts the default parameters that need to be configured for the MySQLDeadLckTest.

• The TEST PERIOD list box helps the user to choose how often should the test be executed.

• In the DATABASE text box, specify the name of a database on the target MySQL database server being monitored.

• The eG agent has to be configured with the credentials of a user who has server-wide Process and Select privileges on the monitored MySQL server. Specify the credentials of such a user in the USERNAME and PASSWORD text boxes. To know how to create such a user, refer to Configuring the eG Agent with Access Privileges topic in the Monitoring MySQL Server document.

• Confirm the password by retyping it in the CONFIRM PASSWORD text box.

• Once the above values are provided, click on the UPDATE button to register the changes made.

When changing default configurations of tests, the values with “$” indicate variables that will be replaced by the eG system according to the specific server being managed - for instance, $hostName is the host/nickname of the target host, $port is the port number of the server being monitored. E.g., for a server xyz:80, $hostName will be changed automatically by the eG manager to “xyz” and $port will be changed to “80” when configuring a test.