MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
The following functions enable you to inspect and configure the Group Replication communication protocol version that is used by a replication group.
group_replication_get_communication_protocol()
Inspect the Group Replication communication protocol version that is currently in use for a group.
Syntax:
STRING group_replication_get_communication_protocol()
This function has no parameters.
Return value:
The oldest MySQL Server version that can join this group and
use the group's communication protocol. Versions from MySQL
5.7.14 allow compression of messages, and versions from
MySQL 8.0.16 also allow fragmentation of messages. Note that
the
group_replication_get_communication_protocol()
UDF returns the minimum MySQL version that the group
supports, which might differ from the version number that
was passed to the
group_replication_set_communication_protocol()
UDF, and from the MySQL Server version that is installed on
the member where you use the UDF.
If the protocol cannot be inspected because this server instance does not belong to a replication group, an error is returned as a string.
Example:
SELECT group_replication_get_communication_protocol();
+------------------------------------------------+
| group_replication_get_communication_protocol() |
+------------------------------------------------+
| 8.0.16 |
+------------------------------------------------+
For more information, see Section 18.4.1.4, “Setting a Group's Communication Protocol Version”.
group_replication_set_communication_protocol()
Downgrade the Group Replication communication protocol
version of a group so that members at earlier releases can
join, or upgrade the Group Replication communication
protocol version of a group after upgrading MySQL Server on
all members. The
GROUP_REPLICATION_ADMIN
privilege is required to use this UDF, and all existing
group members must be online when you issue the statement,
with no loss of majority.
For MySQL InnoDB cluster, the communication protocol version is managed automatically whenever the cluster topology is changed using AdminAPI operations. You do not have to use these UDFs yourself for an InnoDB cluster.
Syntax:
STRING group_replication_set_communication_protocol(version
)
Arguments:
version
: For a downgrade,
specify the MySQL Server version of the prospective
group member that has the oldest installed server
version. In this case, the command makes the group fall
back to a communication protocol compatible with that
server version if possible. The minimum server version
that you can specify is MySQL 5.7.14. For an upgrade,
specify the new MySQL Server version to which the
existing group members have been upgraded.
Return value:
A string containing the result of the operation, for example whether it was successful or not.
Example:
SELECT group_replication_set_communication_protocol("5.7.25");
For more information, see Section 18.4.1.4, “Setting a Group's Communication Protocol Version”.