19.1.5.8 Monitoring Multi-Source Replication

To monitor the status of replication channels the following options exist:

• Using the replication Performance Schema tables. The first column of these tables is Channel_Name. This enables you to write complex queries based on Channel_Name as a key. See Section 29.12.11, “Performance Schema Replication Tables”.

• Using SHOW REPLICA STATUS FOR CHANNEL channel. By default, if the FOR CHANNEL channel clause is not used, this statement shows the replica status for all channels with one row per channel. The identifier Channel_name is added as a column in the result set. If a FOR CHANNEL channel clause is provided, the results show the status of only the named replication channel.

Note

The SHOW VARIABLES statement does not work with multiple replication channels. The information that was available through these variables has been migrated to the replication performance tables. Using a SHOW VARIABLES statement in a topology with multiple channels shows the status of only the default channel.

The error codes and messages that are issued when multi-source replication is enabled specify the channel that generated the error.

19.1.5.8.1 Monitoring Channels Using Performance Schema Tables

This section explains how to use the replication Performance Schema tables to monitor channels. You can choose to monitor all channels, or a subset of the existing channels.

To monitor the connection status of all channels:

mysql> SELECT * FROM replication_connection_status\G;
*************************** 1. row ***************************
CHANNEL_NAME: source_1
GROUP_NAME:
SOURCE_UUID: 046e41f8-a223-11e4-a975-0811960cc264
THREAD_ID: 24
SERVICE_STATE: ON
COUNT_RECEIVED_HEARTBEATS: 0
LAST_HEARTBEAT_TIMESTAMP: 0000-00-00 00:00:00
RECEIVED_TRANSACTION_SET: 046e41f8-a223-11e4-a975-0811960cc264:4-37
LAST_ERROR_NUMBER: 0
LAST_ERROR_MESSAGE:
LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00
*************************** 2. row ***************************
CHANNEL_NAME: source_2
GROUP_NAME:
SOURCE_UUID: 7475e474-a223-11e4-a978-0811960cc264
THREAD_ID: 26
SERVICE_STATE: ON
COUNT_RECEIVED_HEARTBEATS: 0
LAST_HEARTBEAT_TIMESTAMP: 0000-00-00 00:00:00
RECEIVED_TRANSACTION_SET: 7475e474-a223-11e4-a978-0811960cc264:4-6
LAST_ERROR_NUMBER: 0
LAST_ERROR_MESSAGE:
LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00
2 rows in set (0.00 sec)

In the above output there are two channels enabled, and as shown by the CHANNEL_NAME field they are called source_1 and source_2.

The addition of the CHANNEL_NAME field enables you to query the Performance Schema tables for a specific channel. To monitor the connection status of a named channel, use a WHERE CHANNEL_NAME=channel clause:

mysql> SELECT * FROM replication_connection_status WHERE CHANNEL_NAME='source_1'\G
*************************** 1. row ***************************
CHANNEL_NAME: source_1
GROUP_NAME:
SOURCE_UUID: 046e41f8-a223-11e4-a975-0811960cc264
THREAD_ID: 24
SERVICE_STATE: ON
COUNT_RECEIVED_HEARTBEATS: 0
LAST_HEARTBEAT_TIMESTAMP: 0000-00-00 00:00:00
RECEIVED_TRANSACTION_SET: 046e41f8-a223-11e4-a975-0811960cc264:4-37
LAST_ERROR_NUMBER: 0
LAST_ERROR_MESSAGE:
LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00
1 row in set (0.00 sec)

Similarly, the WHERE CHANNEL_NAME=channel clause can be used to monitor the other replication Performance Schema tables for a specific channel. For more information, see Section 29.12.11, “Performance Schema Replication Tables”.