SwitchReads

Route reads to target keyspace

Command

SwitchReads  [-cells=<cells>] [-reverse] [-dry-run] 
             -tablet_type={replica|rdonly} <keyspace.workflow>

Description

SwitchReads is used to switch reads for tables in a MoveTables workflow or for entire keyspace to the target keyspace in a Reshard workflow.

Parameters

-cells

optional
default all

Comma separated list of cells or cell aliases in which reads should be switched in the target keyspace

-reverse

optional
default false

When a workflow is setup the routing rules are setup so that reads/writes to the target shards still go to the source shard since the target is not yet setup. If SwitchReads is called without -reverse then the routing rules for the target keyspace are setup to actually use it. It is assumed that the workflow was successful and user is ready to use the target keyspace now.

However if, for any reason, we want to abort this workflow using the -reverse flag deletes the rules that were setup and vtgate will route the queries to this table to the the source table. There is no way to reverse the use of the -reverse flag other than by recreating the routing rules again using the vtctl ApplyRoutingRules command.

-dry-run

optional
default false

You can do a dry run where no actual action is taken but the command logs all the actions that would be taken by SwitchReads.

-tablet_type

mandatory

On which type of tablets should be reads be switched to the target keyspace. One of replica or rdonly. rdonly tables should be switched first before replica tablets.

keyspace.workflow

mandatory

Name of target keyspace and the associated workflow to SwitchReads for.