MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4
This section describes the status variables providing information about Group Replication.
The status variables and their meanings are listed here:
          Gr_all_consensus_proposals_count
        
Sum of all proposals that were initiated and terminated on this node.
          The total elapsed time for all consensus rounds started and
          finished on this node. By comparing this value with
          Gr_all_consensus_proposals_count,
          we can determine whether a given consensus time has an upward
          trend, which may signal a problem.
        
          Gr_certification_garbage_collector_count
        
The number of times certification garbage collection has been run.
          Gr_certification_garbage_collector_time_sum
        
Sum of the times in microseconds taken by certification garbage collection.
          Gr_consensus_bytes_received_sum
        
The sum of all socket-level bytes received from group nodes having this node as a destination.
Sum of all socket-level bytes originating on this node that were sent to all (other) group nodes. More data is reported here than for sent messages, since they are multiplexed and sent to each member.
For example, if we have a group with three members and we send a 100-byte message, this value accounts for 300 bytes, since we send 100 bytes to each node.
          Gr_control_messages_sent_count
        
Number of control messages sent by this member.
          Gr_control_messages_sent_bytes_sum
        
Sum of the number of bytes used in control messages sent by this member; this is the on-the-wire size.
          Gr_control_messages_sent_roundtrip_time_sum
        
Sum of the round-trip times in microseconds for control messages sent by this member; a round trip is measured between the sending and the delivery of the message on the sender. This should provide the time between sending and delivery of control messages for the majority of the members of the group, including the sender.
          Gr_data_messages_sent_bytes_sum
        
Sum in bytes used by data messages sent by this member; this is the on-the-wire size.
This is the nmber of transaction data messages sent by this member.
          Gr_data_messages_sent_roundtrip_time_sum
        
Sum of the round-trip times in microseconds for data messages sent by this member; a round trip is measured between the sending and the delivery of the message on the sender. This should provide the time between sending and delivery of data messages for the majority of the members of the group, including the sender.
          Gr_empty_consensus_proposals_count
        
Sum of all empty proposal rounds that were initiated and terminated on this node.
          The number of full 3-phase rounds that this node has
          initiated. If this number grows over time, it means that at
          least one node is having problems answering to proposals,
          either due to something it to run slowly, or to network
          issues. Use this value together with the
          count_member_failure_suspicions column of
          the Performance Schema
          replication_group_communication_information
          table when diagnosing such issues.
        
          Gr_last_consensus_end_timestamp
        
The time when the last consensus proposal was approved, in a timestamp format. This can be an indicator whether the group is making slow progress, or has halted.
The number of high-level messages sent by this node to the group. These are the messages received from the API for proposing to the group. The XCom batching mechanism batches these messages and proposes them all together. The value shown for this variable reflects the number of messages prior to batching.
          Gr_transactions_consistency_after_sync_count
        
          Number of transactions on secondaries that waited to start,
          while waiting for transactions from the primary with
          group_replication_consistency
          equal to AFTER or
          BEFORE_AND_AFTER to be committed.
        
          Gr_transactions_consistency_after_sync_time_sum
        
          Sum of the times in microseconds that transactions on
          secondaries waited on transactions from the primary with
          group_replication_consistency
          equal to AFTER or
          BEFORE_AND_AFTER to be committed, before
          starting.
        
          Gr_transactions_consistency_after_termination_count
        
          The number of transactions executed with
          group_replication_consistency
          equal to AFTER or
          BEFORE_AND_AFTER.
        
          Gr_transactions_consistency_after_termination_time_sum
        
          Sum of the time in microseconds between delivery of the
          transaction executed with
          group_replication_consistency
          equal to AFTER or
          BEFORE_AND_AFTER, and acknowledgement by
          the other group members that the transaction is prepared.
        
This value does not include transaction send roundtrip time.
          Gr_transactions_consistency_before_begin_count
        
          Number of transactions executed with
          group_replication_consistency
          equal to BEFORE or
          BEFORE_AND_AFTER.
        
          Gr_transactions_consistency_before_begin_time_sum
        
          Sum of the time in microseconds that the member waited until
          its group replication applier channel was consumed before
          executing the transaction with
          group_replication_consistency
          equal to BEFORE or
          BEFORE_AND_AFTER.
        
These status variables all have member scope since they reflect what the local member observes. They are reset on group bootstrap, joining of a new member, automatic rejoin of an existing member, and server restart.