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17.4.1.16 Replication of Invoked Features

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Replication of invoked features such as user-defined functions (UDFs) and stored programs (stored procedures and functions, triggers, and events) provides the following characteristics:

  • The effects of the feature are always replicated.

  • The following statements are replicated using statement-based replication:

    However, the effects of features created, modified, or dropped using these statements are replicated using row-based replication.

    Note

    Attempting to replicate invoked features using statement-based replication produces the warning Statement is not safe to log in statement format. For example, trying to replicate a UDF with statement-based replication generates this warning because it currently cannot be determined by the MySQL server whether the UDF is deterministic. If you are absolutely certain that the invoked feature's effects are deterministic, you can safely disregard such warnings.

  • In the case of CREATE EVENT and ALTER EVENT:

  • The feature implementation resides on the slave in a renewable state so that if the master fails, the slave can be used as the master without loss of event processing.

To determine whether there are any scheduled events on a MySQL server that were created on a different server (that was acting as a replication master), query the INFORMATION_SCHEMA.EVENTS table in a manner similar to what is shown here:

  1. SELECT EVENT_SCHEMA, EVENT_NAME
  2.     FROM INFORMATION_SCHEMA.EVENTS
  3.     WHERE STATUS = 'SLAVESIDE_DISABLED';

Alternatively, you can use the SHOW EVENTS statement, like this:

  1. SHOW EVENTS
  2.     WHERE STATUS = 'SLAVESIDE_DISABLED';

When promoting a replication slave having such events to a replication master, you must enable each event using ALTER EVENT event_name ENABLE, where event_name is the name of the event.

If more than one master was involved in creating events on this slave, and you wish to identify events that were created only on a given master having the server ID master_id, modify the previous query on the EVENTS table to include the ORIGINATOR column, as shown here:

  1. SELECT EVENT_SCHEMA, EVENT_NAME, ORIGINATOR
  2.     FROM INFORMATION_SCHEMA.EVENTS
  3.     WHERE STATUS = 'SLAVESIDE_DISABLED'
  4.     AND   ORIGINATOR = 'master_id'

You can employ ORIGINATOR with the SHOW EVENTS statement in a similar fashion:

  1. SHOW EVENTS
  2.     WHERE STATUS = 'SLAVESIDE_DISABLED'
  3.     AND   ORIGINATOR = 'master_id'

Before enabling events that were replicated from the master, you should disable the MySQL Event Scheduler on the slave (using a statement such as SET GLOBAL event_scheduler = OFF;), run any necessary ALTER EVENT statements, restart the server, then re-enable the Event Scheduler on the slave afterward (using a statement such as SET GLOBAL event_scheduler = ON;)-

If you later demote the new master back to being a replication slave, you must disable manually all events enabled by the ALTER EVENT statements. You can do this by storing in a separate table the event names from the SELECT statement shown previously, or using ALTER EVENT statements to rename the events with a common prefix such as replicated_ to identify them.

If you rename the events, then when demoting this server back to being a replication slave, you can identify the events by querying the EVENTS table, as shown here:

  1. SELECT CONCAT(EVENT_SCHEMA, '.', EVENT_NAME) AS 'Db.Event'
  2.       FROM INFORMATION_SCHEMA.EVENTS
  3.       WHERE INSTR(EVENT_NAME, 'replicated_') = 1;

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Document created the 26/06/2006, last modified the 26/10/2018
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