14.3 Replication

Note

MySQL Enterprise Monitor is available as part of the MySQL Enterprise subscription, learn more at http://www.mysql.com/products/.

Navigate to the Replication page by choosing Replication under Dashboards. This page summarizes the state of your replication servers; you can drill down to see details about any master or slave. Using this page helps you avoid running the SHOW SLAVE STATUS command over and over on multiple servers; for consistency, the Replication page uses some of the same keywords as the output from that command.

Note

Set up agents to monitor each master and slave server. Only servers that are monitored appear on this page.

The Replication page groups all master servers with their slaves. Masters and their slaves are autodiscovered and a grouping is created, based on the way that the servers are interconnected (known as the replication topology). Scans run on a five minute interval, so depending upon the order of discovery, it can take as long as 2 polling intervals to create a complete group.

Discovery events are logged to the Replication log. To view this log, navigate to the Settings page and choose the Logs link. View all replication-related events by clicking the Replication link. This log can be a useful tool for debugging the replication topology discovery process.

Warning

Auto-discovery with remote monitoring only functions with MySQL 5.6 and later. Earlier versions of MySQL server require the Agent to be installed on the same host as the monitored MySQL instance. This is because mysqld did not expose the master's uuid value via SHOW SLAVE STATUS until version 5.6.

You can manage replication groups from the MySQL Instances page in the same way as other groups. However, any slaves removed from a server group are automatically restored to that group. You can also add non-slaves to a replication grouping.

Note

The replication group name can also be edited from the Replication dashboard by clicking the drop-down menu for the group, and choosing Rename Group.

Replication Page Details

Choose a value from the Refresh drop-down list box to set the rate at which information is updated. This refresh rate applies only to the information presented on this page: It is independent of the rate set for the Monitor tab.

The following columns describe replication master and slave servers:

  • Servers: Displays the group name and any servers that are part of the group. Levels of indentation in this column show the relationship between master servers and their slaves. The icon next to each server indicates if the server is enabled for semi-synchronous replication or not. A gray disabled-style icon indicates that semi-synchronous replication is not available.

  • Type: Indicates the topology of a server group or in the case of individual servers, whether a server is a master, a combined master/slave, or a slave.

  • Threads: Displays information about the two dedicated replication threads that run on the slave server. Both threads must be running for the slave to work properly. IO reports the status of the slave I/O thread. SQL reports the status of the slave SQL thread.

  • Time Behind: The interval that the slave is behind the master, in hh:mm:ss format. This column is blank if a server is a master. Typically, you try to keep this value low.

  • Binary Logs: Displays information about the binary log file. Current File shows the binary log file name. Position shows the current position in the binary log file.

  • Master Position: Displays information about the binary log position from the master server. Binary Log shows the master binary log file name. Position shows the current position in the master binary log file.

  • Log Space: Displays the sizes of log files related to replication. Binary Logs shows size information for the binary log files. Relay Logs shows size information for the relay log files.

Most column headings are active links; click the header to change the display order. Sorting works differently for different column groupings. Click the Time Behind header to order servers by the number of seconds they are behind their master. The server topology is respected regardless of sort order. For example, in a TREE topology, ordering occurs within branches only.

If the Agent is down, instances show in bold red in the Servers column. The Slave IO and the Slave SQL columns display stopped in red text if these threads are not running. If an agent is down, the last know status of the IO or SQL threads is shown in italics.

Clicking a master server opens a dialog box that displays information about the server. The information shown includes:

  • The number of slave servers.

  • The binary log file name.

  • The binary log position.

  • Which databases are replicated and which not.

  • GTID values, for MySQL servers 5.6 and above.

The dialog box also includes a link to hide or show the slave servers.

Clicking a slave server opens a dialog window showing extensive information about the slave.

Deleted Replication Groups

This section describes the how replication groups are treated if the replication topology changes.

  • If all instances which make up a replication group are deleted, the replication group is deleted automatically.

    If a replication group is automatically deleted, an event is generated and a message is displayed in the MySQL Enterprise Monitor User Interface.

  • If the deleted replication group was associated with an event handler, the replication group is automatically removed from the event handler's definition.

    An event is generated and a message is displayed in the MySQL Enterprise Monitor User Interface stating that the group was removed.

  • If the deleted replication group was the only filter defined on the event handler, the event handler is suspended.

    An event is generated and a message is displayed in the MySQL Enterprise Monitor User Interface stating that the group was removed and the event handler suspended.

Usage Notes

For information on the kinds of problems you might find while monitoring replication, and how to solve them, see Troubleshooting Replication and Improving Replication Performance.