MySQL 9.3 Reference Manual Including MySQL NDB Cluster 9.3
This table shows group configuration options for the whole replication group. The table is available only when Group Replication is installed.
The
replication_group_communication_information
table has these columns:
WRITE_CONCURRENCY
The maximum number of consensus instances that the group can execute in parallel. The default value is 10. See Section 20.5.1.3, “Using Group Replication Group Write Consensus”.
PROTOCOL_VERSION
The Group Replication communication protocol version, which determines what messaging capabilities are used. This is set to accommodate the oldest MySQL Server version that you want the group to support. See Section 20.5.1.4, “Setting a Group's Communication Protocol Version”.
WRITE_CONSENSUS_LEADERS_PREFERRED
The leader or leaders that Group Replication has
instructed the group communication engine to use to drive
consensus. For a group in single-primary mode with the
group_replication_paxos_single_leader
system variable set to ON
and the
communication protocol version set to 8.0.27 or later, the
single consensus leader is the group's primary.
Otherwise, all group members are used as leaders, so they
are all shown here. See
Section 20.7.3, “Single Consensus Leader”.
WRITE_CONSENSUS_LEADERS_ACTUAL
The actual leader or leader that the group communication engine is using to drive consensus. If a single consensus leader is in use for the group, and the primary is currently unhealthy, the group communication selects an alternative consensus leader. In this situation, the group member specified here can differ from the preferred group member.
WRITE_CONSENSUS_SINGLE_LEADER_CAPABLE
Whether the replication group is capable of using a single
consensus leader. 1 means that the group was started with
the use of a single leader enabled
(group_replication_paxos_single_leader
= ON
), and this is still shown if the value of
group_replication_paxos_single_leader
has since been changed on this group member. 0 means that
the group was started with single leader mode disabled
(group_replication_paxos_single_leader
= OFF
), or has a Group Replication communication
protocol version that does not support the use of a single
consensus leader (prior to 8.0.27). This information is
only returned for group members in
ONLINE
or RECOVERING
state.
MEMBER_FAILURE_SUSPICIONS_COUNT
The address of each group member paired with the number of times this member has been seen as suspect by the local node. This information is displayed in JSON format. For a group with three members, the value of this column should appear similar to what is shown here:
{ "d57da302-e404-4395-83b5-ff7cf9b7e055": 0, "6ace9d39-a093-4fe0-b24d-bacbaa34c339": 10, "9689c7c5-c71c-402a-a3a1-2f57bfc2ca62": 0 }
The
replication_group_communication_information
table has no indexes.
TRUNCATE TABLE
is not permitted
for the
replication_group_communication_information
table.