Book Image

Cassandra High Availability

By : Robbie Strickland
Book Image

Cassandra High Availability

By: Robbie Strickland

Overview of this book

Table of Contents (16 chapters)
Cassandra High Availability
About the Author
About the Reviewers

Token assignment

In Cassandra terminology, the start of the hash range is called a token, and until version 1.2, each node was assigned a single token in the manner discussed in the previous section. Version 1.2 introduced the option to use vnodes, as the feature is officially termed. vnodes became the default option in the 2.0 release.

Cassandra determines where to place data using the tokens assigned to each node. Nodes learn about these token assignments via gossip. Additional replicas are then placed based on the configured replication strategy and snitch. More details about replica placement can be found in Chapter 3, Replication.

Manually assigned tokens

If you're running a version prior to 1.2 or if you have chosen not to use vnodes, you will have to assign tokens manually. This is accomplished by setting the initial_token in cassandra.yaml.

Manual token assignment introduces a number of potential issues:

  • Adding and removing nodes: When the size of the ring changes, all tokens must be...