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The Group Replication Flow Control Statistics component (component_group_replication_flow_control_stats) enables a number of global status variables which provide information on Group Replication flow control execution. This component is available in MySQL 9.1 and later as part of MySQL Enterprise Edition.

Prior to installing the Group Replication Flow Control Statistics component, the Group Replication plugin must be installed usingINSTALL PLUGIN or--plugin-load-add (seeSection 20.2.1.2, “Configuring an Instance for Group Replication”); otherwise, theINSTALL COMPONENT statement is rejected with the errorCannot satisfy dependency for service 'group_replication_flow_control_metrics_service' required by component 'mysql:group_replication_flow_control_stats'. If you attempt to uninstall the Group Replication plugin when the Group Replication Flow Control Statistics component is installed,UNINSTALL PLUGIN fails with the errorPlugin 'group_replication' cannot be uninstalled now. Please uninstall the component 'component_group_replication_flow_control_stats' and then UNINSTALL PLUGIN group_replication.

Provided that these conditions are met, The Group Replication Flow Control Statistics component can be installed and uninstalled usingINSTALL COMPONENT andUNINSTALL COMPONENT, respectively. See the descriptions of these statements, as well asSection 7.5.1, “Installing and Uninstalling Components”, for more information.

The Group Replication Flow Control Statistics component provides the global status variables listed here with their meanings:

The values of these variables can be obtained by querying the Performance Schemaglobal_status table, as shown here:

mysql> SELECT * FROM performance_schema.global_status    -> WHERE VARIABLE_NAME LIKE 'Gr_flow_control%';+--------------------------------------------------+---------------------+| VARIABLE_NAME                                  | VARIABLE_VALUE      |+--------------------------------------------------+---------------------+| Gr_flow_control_throttle_active_count          | 10                  |+--------------------------------------------------+---------------------+| Gr_flow_control_throttle_count                 | 10                  |+--------------------------------------------------+---------------------+| Gr_flow_control_throttle_last_throttle_timestamp | 2024-07-01 12:50:56 |+--------------------------------------------------+---------------------+| Gr_flow_control_throttle_time_sum              | 10                  |+--------------------------------------------------+---------------------+

You can also observe these values in the output ofSHOW GLOBAL STATUS, like this:

mysql> SHOW GLOBAL STATUS LIKE 'Gr\_flow\_control%';+--------------------------------------------------+---------------------+| Variable_Name                                  | Value               |+--------------------------------------------------+---------------------+| Gr_flow_control_throttle_active_count          | 10                  |+--------------------------------------------------+---------------------+| Gr_flow_control_throttle_count                 | 10                  |+--------------------------------------------------+---------------------+| Gr_flow_control_throttle_last_throttle_timestamp | 2024-07-01 12:50:56 |+--------------------------------------------------+---------------------+| Gr_flow_control_throttle_time_sum              | 10                  |+--------------------------------------------------+---------------------+

All of the status variables listed previously are reset whenever any of the following events occurs:

Since they reflect what what the local member observes, all of these status variables have member scope.