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MySQL 5.7 Reference Manual  /  ...  /  Replication_group_member_stats

17.3.1 Replication_group_member_stats

Each member in a replication group certifies and applies transactions committed by the group. Statistics regarding the certifier and applier procedures are useful to understand how the applier queue is growing, how many conflicts have been found, how many transactions were checked, which transactions are committed everywhere, and so on. The table performance_schema.replication_group_member_stats provides the following information related to the certification process.

Table 17.1 replication_group_member_stats

Field

Description

Channel_name

The name of the Group Replication channel.

Member_id

This gives the member server UUID to which we are currently connected to. This has a different value for each member in the group. This also serves a key since it is unique to each member.

Count_Transactions_in_queue

Number of transactions in queue pending conflict detection checks. Once checked for conflicts, and if they pass the check, they are queued to be applied as well.

Count_transactions_checked

Indicates the number of transactions that were checked for conflicts.

Count_conflicts_detected

Indicates the number of transactions that did not pass the conflict detection check.

Count_transactions_validating

Indicates the current size of the conflict detection database (against which each transaction is certified).

Transactions_committed_all_members

Indicates those transactions that have been successfully committed on all members of the current view. This is updated at a fixed time interval.

Last_conflict_free_transaction

Shows the transaction identifier of the last conflict free transaction checked.


These fields are important for monitoring the performance of the members connected in the group. For example, suppose that one of the group’s members is delayed and is not able to keep up to date with the other members of the group. In this case you might see a large number of transactions in the queue. Based on this information, you could decide to either remove the member from the group or delay the processing of transactions on the other members of the group thus reducing the number of queued transactions. This information can can also help you to decide how to adjust the flow control of the Group Replication plugin.


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