How to Switch Snitches

This procedure describes the steps that need to be done when switching from one type of snitch to another. Such scenario can be when increasing the cluster and adding more data-centers in different locations. Snitches are responsible how Scylla will distribute the replicas, the procedure depends if there are any changes in the cluster topology.

Note - Switching a snitch require full cluster shutdown, so It is highly recommended to choose the right snitch for your needs at cluster setup phase.

Cluster Status Needed Procedure
No change in network topology Set the new snitch
Network topology was changed Set the new snitch and run repair

Changes in network topology mean that there are changes in the racks or data-centers where the nodes are located.

For example:

No topology changes

Original cluster: three nodes cluster on a single data-center with Simplesnitch or Ec2snitch.

Change to: three nodes in one datacenter and one rack using a GossipingPropertyFileSnitch or Ec2multiregionsnitch.

Topology changes

Original cluster: three nodes using the Simplesnitch or Ec2snitch in a single datacenter.

Change to: nine nodes in two data-centers using the GossipingPropertyFileSnitch or Ec2multiregionsnitch (add a new data-center).

Procedure

  1. Stop all the nodes in the cluster.

CentOS, RHEL or Ubuntu 16.04

sudo systemctl stop scylla-server

Ubuntu 14.04 or Debian

sudo service scylla-server stop
  1. 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

  1. 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.

  1. Start the nodes in the cluster one by one.

CentOS, RHEL or Ubuntu 16.04

sudo systemctl start scylla-server

Ubuntu 14.04 or Debian

sudo service scylla-server start
  1. Run full repair (consult with the table above if this action is needed).

Procedures