A VTTablet is the Vitess component that both front-ends and, optionally, controls a running MySQL server. It accepts queries over gRPC and translates the queries back to MySQL, as well as speaking to MySQL to issue commands to control replication, take backups, etc.
Things to note about VTTablet are:
- There needs to be a one to one mapping of MySQLd and each VTTablet.
- VTTablet will track long running queries and for how long they have run. It also will kill the long running queries itself.
- VTTablet will create a sidecar database when running to store the local state of the cluster.
- The combination of a VTTablet process and a MySQL process is called a Tablet.
Please do note that in some cases VTTablets may be deployed as unmanaged/remote or partially managed. You can read about that here.