Generating tokens¶

Calculating tokens for single or multiple data centers¶

When calculating tokens for single data center deployments, you calculate tokens by dividing the hash range by the number of nodes in the cluster. For 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 RandomPartitioner¶

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

Calculating tokens for the Murmur3Partitioner¶

Use this method for generating tokens when you are not using virtual nodes and using the Murmur3Partitioner (default). This partitioner uses a maximum possible range of hash values from -2⁶³ to +2⁶³-1. 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']