Switching snitches
Steps for switching snitches.
Because snitches determine how
Cassandra distributes replicas, the procedure to switch snitches depends on whether
or not the topology of the cluster will change:
- If data has not been inserted into the cluster, there is no change in the network topology. This means that you only need to set the snitch; no other steps are necessary.
- If data has been inserted into the cluster, it's possible that the topology has changed and you will need to perform additional steps.
A change in topology means that there is a change in the data centers and/or racks
where the nodes are placed. Topology changes may occur when the replicas are placed
in different places by the new snitch. Specifically,
the replication strategy places the replicas based on the information provided by the new
snitch. The following examples
demonstrate the differences:
- No topology change
Suppose you have 5 nodes using the SimpleSnitch in a single data center and you change to 5 nodes in 1 data center and 1 rack using a network snitch such as the GossipingPropertyFileSnitch.
- Topology changes
- Suppose you have 5 nodes using the SimpleSnitch in a single data
center and you change to 5 nodes in 2 data centers using the PropertyFileSnitch.Note: If splitting from one data center to two, you need to change the schema for the keyspace that are splitting. Additionally, the data center names must change accordingly.
- Changing the name of a data center is a topology change.
- Suppose you have 5 nodes using the SimpleSnitch in a single data
center and you change to 5 nodes in 2 data centers using the PropertyFileSnitch.
- Topology change
Suppose you have 5 nodes using the SimpleSnitch in a single data center and you change to 5 nodes in 1 data center and 2 racks using the RackInferringSnitch.