vtgr is a stateless orchestration component that integrates Vitess with MySQL group replication: it is responsible to bootstrap MySQL group and reconcile between the group and Vitess. It is available as an experimental feature. It still needs thorough testing, and more features need to be added.

In order to configure vtgr, you have to make the following changes to vttablet:

• Add -db_flavor=MysqlGR: This will allow vttablet to understand stats in group replication.
• Add -disable_active_reparents=true: This part will prevent vttablet from fixing replication, and will rely on vtgr instead.

vtgr requires two config files vtgr_config and db_config to be launched:

• vtgr_config: controls desired group parameters. A sample is available here.

BootstrapGroupSize configs the desired size of group. vtgr will only bootstrap a mysql group for a shard when it discovers desired number of healthy node from topology.

• db_config: controls connection parameters that vtgr uses. As an example:

{
  "MySQLTopologyUser": "vtgr_user",
  "MySQLTopologyPassword": "vtgr_password",
  "MySQLReplicaUser": "vtgr_user",
  "MySQLReplicaPassword": "vtgr_password",
}

You can bring vtgr using the following invocation:

vtgr <topo_flags> \
  -log_dir=${VTDATAROOT}/tmp \
  -vtgr_config vtgr.json \
  -db_config db.json \
  -clusters_to_watch ks/0 \

Bringing up vtgr should immediately cause a primary to be elected among the vttablets that have come up.

You can optionally add a clusters_to_watch flag that contains a comma separated list of keyspaces or keyspace/shard values. If specified, vtgr will manage only those clusters.