How to Switch Snitches

.. note::

Changing the network topology by switching to another type of snitch
is no longer supported. The new snitch must specify the same DC and rack
as the previous one.

This procedure describes the steps that need to be done when switching from one type of snitch to another. Such a scenario can be when increasing the cluster and adding more data-centers in different locations. Snitches are responsible for specifying how ScyllaDB distributes the replicas. The procedure is dependent on any changes in the cluster topology.

Note - Switching a snitch requires a full cluster shutdown, so It is highly recommended to choose the :doc:right snitch </operating-scylla/system-configuration/snitch> for your needs at the cluster setup phase.

For example:

Original cluster: three nodes cluster on a single data-center with :ref:Simplesnitch <snitch-simple-snitch> or :ref:Ec2snitch <snitch-ec2-snitch>.

Change to: three nodes in one data-center and one rack using a :ref:GossipingPropertyFileSnitch <snitch-gossiping-property-file-snitch> or :ref:Ec2multiregionsnitch <snitch-ec2-multi-region-snitch>.

Procedure

Stop all the nodes in the cluster.

.. include:: /rst_include/scylla-commands-stop-index.rst

In the scylla.yaml file edit the endpoint_snitch. The file can be found under /etc/scylla/. Change the endpoint_snitch to all the nodes in the cluster.

For example:

endpoint_snitch: GossipingPropertyFileSnitch

In the cassandra-rackdc.properties file edit the rack and data-center information.

For example, Ec2MultiRegionSnitch:

A node in the us-east-1 region, us-east is the data center name, and 1 is the rack location.

Start all the nodes in the cluster in parallel.

.. include:: /rst_include/scylla-commands-start-index.rst

Run full repair (consult with the table above if this action is needed).