Initializing single-token architecture datacenters 

Steps for deploying when you are not using virtual nodes (vnodes).

In most circumstances, each workload type, such as search, analytics, and transactional, should be organized into separate virtual datacenters. Workload segregation avoids contention for resources. However, workloads can be combined in SearchAnalytics nodes when there is not a large demand for analytics, as combining transactional (OLTP) and analytics (OLAP) workloads result in decreases performance. You can enable DSE Graph only on the nodes you want to query.

When you create a keyspace using CQL, Cassandra creates a virtual datacenter for a cluster, even a one-node cluster, automatically. You assign nodes that run the same type of workload to the same datacenter. The separate, virtual datacenters for different types of nodes segregate workloads that run DSE Search from those nodes that run other workload types.

In this scenario, a mixed workload cluster has only one datacenter for each type of workload. For example, if the cluster has 3 analytics nodes, 3 Cassandra nodes, and 2 DSE Search nodes, the cluster would have 3 datacenters, one for each type of workload. In contrast, a multiple data-center cluster has more than one datacenter for each type of workload.

Prerequisites

Procedure

These steps provide information about setting up a having one or more datacenters.

  1. Suppose you install DataStax Enterprise on these nodes:
    • node0 10.168.66.41 (seed1)
    • node1 10.176.43.66
    • node2 10.168.247.41
    • node3 10.176.170.59 (seed2)
    • node4 10.169.61.170
    • node5 10.169.30.138
  2. Calculate the token assignments as described in Calculating tokens for single-token architecture nodes.

    Tokens for a 6 node cluster with a single datacenter or two datacenters.

    Single Datacenter
    Node Token
    node0 0
    node1 21267647932558653966460912964485513216
    node2 42535295865117307932921825928971026432
    node3 63802943797675961899382738893456539648
    node4 85070591730234615865843651857942052864
    node5 106338239662793269832304564822427566080
    Multiple Datacenters
    Node Token Offset Datacenter
    node0 0 NA DC1
    node1 56713727820156410577229101238628035242 NA DC1
    node2 113427455640312821154458202477256070485 NA DC1
    node3 100 100 DC2
    node4 56713727820156410577229101238628035342 100 DC2
    node5 113427455640312821154458202477256070585 100 DC2
  3. If the nodes are behind a firewall, open the required ports for internal/external communication.
  4. If DataStax Enterprise is running, stop the nodes and clear the data:
    • Installer-Services and Package installations:
      $ sudo service dse stop
      $ sudo rm -rf /var/lib/cassandra/*  # Clears the data from the  default directories
    • Installer-No Services and Tarball installations:

      From the install directory:

      $ sudo bin/dse cassandra-stop
      $ sudo rm -rf /var/lib/cassandra/*  # Clears the data from the  default directories 
  5. Set the properties in the cassandra.yaml file for each node.

    If the nodes in the cluster are identical in terms of disk layout, shared libraries, and so on, you can use the same copy of the cassandra.yaml file on all of the nodes.

    The default location of the cassandra-topology.properties file depends on the type of installation:
    Installer-Services and Package installations /etc/dse/cassandra/cassandra-topology.properties
    Installer-No Services and Tarball installations install_location/resources/cassandra/conf/cassandra-topology.properties
    The location of the cassandra.yaml file depends on the type of installation:
    Installer-Services /etc/dse/cassandra/cassandra.yaml
    Package installations /etc/dse/cassandra/cassandra.yaml
    Installer-No Services install_location/resources/cassandra/conf/cassandra.yaml
    Tarball installations install_location/resources/cassandra/conf/cassandra.yaml
    The default location of the cassandra-rackdc.properties file depends on the type of installation:
    Installer-Services and Package installations /etc/dse/cassandra/cassandra-rackdc.properties
    Installer-No Services and Tarball installations install_location/resources/cassandra/conf/cassandra-rackdc.properties
    The location of the dse.yaml file depends on the type of installation:
    Installer-Services /etc/dse/dse.yaml
    Package installations /etc/dse/dse.yaml
    Installer-No Services install_location/resources/dse/conf/dse.yaml
    Tarball installations install_location/resources/dse/conf/dse.yaml

    Properties to set:

    • initial_token: token_value_from_calculation
    • num_tokens: 1
    • -seeds: internal_IP_address of each seed node
    • listen_address: empty

      If not set, Cassandra asks the system for the local address, the one associated with its hostname. In some cases Cassandra doesn't produce the correct address and you must specify the list_address.

    • endpoint_snitch: snitch

      See endpoint_snitch and About Snitches. If you are changing snitches, see Switching snitches.

    • auto_bootstrap: false

      Add the bootstrap setting only when initializing a fresh cluster with no data.

    • If you are using a cassandra.yaml or dse.yaml file from a previous version, be sure to check the Upgrade guide for removed settings:

    You must include at least one seed node from each datacenter. DataStax recommends that you have more than one seed node per datacenter. Do not make all nodes seed nodes.

    cluster_name: 'MyDemoCluster'
    initial_token: 21267647932558653966460912964485513216
    num_tokens: 1
    seed_provider:
      - class_name: org.apache.cassandra.locator.SimpleSeedProvider
        parameters:
             - seeds: "10.168.66.41,10.176.170.59"
    listen_address:
    endpoint_snitch: GossipingPropertyFileSnitch
  6. Set the properties in the dse.yaml file as required by your use case.
  7. In the cassandra-rackdc.properties (GossipingPropertyFileSnitch) or cassandra-topology.properties (PropertyFileSnitch) file, use your naming convention to assign datacenter and rack names to the IP addresses of each node, and assign a default datacenter name and rack name for unknown nodes.
    Note: The GossipingPropertyFileSnitch always loads cassandra-topology.properties when that file is present. Remove the file from each node on any new cluster, or any cluster migrated from the PropertyFileSnitch.

    Example:

    # Cassandra Node IP=Datacenter:Rack
    10.168.66.41=DC1:RAC1
    10.176.43.66=DC2:RAC1
    10.168.247.41=DC1:RAC1
    10.176.170.59=DC2:RAC1
    10.169.61.170=DC1:RAC1
    10.169.30.138=DC2:RAC1
    
    # default for unknown nodes
    default=DC1:RAC1
  8. After you have installed and configured DataStax Enterprise on all nodes, start the seed nodes one at a time, and then start the rest of the nodes:
  9. Check that your cluster is up and running:
    • Installer-Services and Package installations: $ nodetool status
    • Installer-No Services and Tarball installations: $ install_location/bin/nodetool status

Results

Datacenter: Cassandra
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address         Load        Tokens    Owns    Host ID             Rack
UN 110.82.155.0    21.33 KB    256       33.3%   a9fa31c7-f3c0-...   RAC1
UN 110.82.155.1    21.33 KB    256       33.3%   f5bb416c-db51-...   RAC1
UN 110.82.155.2    21.33 KB    256       16.7%   b836748f-c94f-...   RAC1