Switch traffic from source to target

Experimental #

This documentation is for a new (v2) set of vtctld commands. See RFC for more details.

Command #

MoveTables/Reshard -v2 [-tablet_types=<tablet_types>] [-cells=<cells>]
  [-timeout=timeoutDuration] [-reverse_replication] [-dry_run]
  SwitchTraffic <targetKs.workflow>

Description #

SwitchTraffic switches traffic forward for the tablet_types specified. This replaces the previous SwitchReads and SwitchWrites commands with a single one. It is also possible now to switch all traffic with just one command. Also, you can now switch replica, rdonly and primary traffic in any order: earlier you needed to first SwitchReads (for replicas and rdonly tablets) first before SwitchWrites.

Parameters #

-cells #

default all cells

A comma-separated list of cell names or cell aliases. Traffic will be switched only in these cells for the specified tablet types.

-tablet_types #

default all (replica,rdonly,master)

A comma-separated list of tablet types for which traffic is to be switched. One or more from master,replica,rdonly.

-timeout #

default 30s

For master tablets, SwitchTraffic first stops writes on the source master and waits for the replication to the target to catchup with the point where the writes were stopped. If the wait time is longer than timeout the command will error out. For setups with high write qps you may need to increase this value.

-reverse_replication #

default true

SwitchTraffic for master tablet types, by default, starts a reverse replication stream with the current target as the source, replicating back to the original source. This enables a quick and simple rollback using ReverseTraffic. This reverse workflow name is that of the original workflow concatenated with _reverse.

If set to false these reverse replication streams will not be created and you will not be able to rollback once you have switched write traffic over to the target.

-dry-run #

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 SwitchTraffic.