Apache Cassandra™ 2.0

Generating tokens

If not using virtual nodes (vnodes), you still need to calculate tokens for your cluster.

The following topics in the Cassandra 1.1 documentation provide conceptual information about tokens:

About calculating tokens for single or multiple data centers in Cassandra 1.2 and later

  • Single data center deployments: calculate tokens by dividing the hash range by the number of nodes in the cluster.
  • Multiple data center deployments: calculate the tokens for each data center so that the hash range is evenly divided for the nodes in each data center.

For more explanation, see be sure to read the conceptual information mentioned above.

The method used for calculating tokens depends on the type of partitioner:

Calculating tokens for the Murmur3Partitioner

Use this method for generating tokens when you are not using virtual nodes (vnodes) and using the Murmur3Partitioner (default). This partitioner uses a maximum possible range of hash values from -2 63 to +2 63 -1. To calculate tokens for this partitioner:

python -c 'print [str(((2**64 / number_of_tokens) * i) - 2**63) for i in range(number_of_tokens)]'

For example, to generate tokens for 6 nodes:

python -c 'print [str(((2**64 / 6) * i) - 2**63) for i in range(6)]'

The command displays the token for each node:

[ '-9223372036854775808', '-6148914691236517206', '-3074457345618258604', 
  '-2', '3074457345618258600', '6148914691236517202' ]

Calculating tokens for the RandomPartitioner

To calculate tokens when using the RandomPartitioner in Cassandra 1.2 clusters, use the Cassandra 1.1 Token Generating Tool.