. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 How do I choose between master vs. replica for queries? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 There . . . . . . . 175 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 Master starts up read-only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 Vitess sees the wrong tablet as master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 User Guides

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 How do I choose between master vs. replica for queries? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 There . . . . . . . 203 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 Master starts up read-only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 Vitess sees the wrong tablet as master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 User Guides

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 How do I choose between master vs. replica for queries? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 There . . . . . . . 167 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Master starts up read-only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Vitess sees the wrong tablet as master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 User Guides

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 How do I choose between master vs. replica for queries? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 There . . . . . . . 224 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 Master starts up read-only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 Vitess sees the wrong tablet as master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 User Guides

264 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 Master starts up read-only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 Master starts up read-only . . . . Vitess sees the wrong tablet as master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 Vitess sees the wrong tablet as master . . . . . . . . . . . . . . .

306 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 Master starts up read-only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 Master starts up read-only . . . . Vitess sees the wrong tablet as master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 Vitess sees the wrong tablet as master . . . . . . . . . . . . . . .

284 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 Elevated query latency on master . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 Master starts up read-only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 Master starts up read-only . . . . Vitess sees the wrong tablet as master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 Vitess sees the wrong tablet as master . . . . . . . . . . . . . . .

information. • primary - A replica tablet that happens to currently be the MySQL primary for its shard. • master - Same as primary. Deprecated. • replica - A MySQL replica that is eligible to be promoted to primary that has been created within the keyspace. For each shard that is active there is an attribute is_master_serving which is set to true. The other shards which have been created but are still not serving queries to this primary during the cutover or before it discovers the new serving graph. OR the is_master_serving parameter is set to false for that shard in the corresponding shard info object. Routing

downtime Vitess Resharding • shard0, shard1, origin master —> vttablet • prepare two spare shard0, shard1 • vtgate point to origin master • multi-snapshot : data & repl-pos • multi-restore shard1 read-only. • shard0, shard1 replication to orign master • set origin master read-only • wait until shard0, shard1 catch origin master. • update configure server, vtgate point to shard0, shard1 vtgate [a-z] [a-m] [n-z] Vitess Snapshot • prepare • set read-only • stop slave • get master position & slave position. • flush tables with read lock • select {.keyspaceIdColumnName}, {

Kings Architecture shard n shard 1 vtgate app server app server app server mysqld vttablet master vtgate big data Vitess lockserver mysqld vttablet mysqld vttablet replicas mysqld vttablet Blacklisting Growing with Vitess Vitess app server app server app server Master Replica Replica routing Load balancing Master promotion with Orchestrator Growing with Vitess Vitess app server app