Configuration of 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.

The default parameters associated with this test are:

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

• In the HOST text box, specify the IP address of the host for which the test is to be configured.

• In the PORT text box, specify the port at which the specified host listens.

• 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.

• The DETAILED DIAGNOSIS makes diagnosis more efficient and accurate, the eG Enterprise embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option. The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability

  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0

• If multiple components of the same component type are awaiting configuration, then an APPLY TO OTHER COMPONENTS check box will appear in this page. Clicking on this check box will allow you to apply the configuration to all/selected components of that type.

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

When changing the configuration for specific servers, a “*” beside the text box corresponding to the parameter signifies that these values have to be manually configured by the user. The parameter values that require to be configured will typically be prefixed with a “$” or contain a series of “*”. A value of "none" in the parameter value indicates that the corresponding parameter value can be changed if required.