Initializing single-token architecture datacenters

Follow these steps only when 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, or when analytics queries must use a DSE Search index. Generally, combining transactional (OLTP) and analytics (OLAP) workloads results in decreased performance.

When creating a keyspace using CQL, DataStax Enterprise 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.

Configuration file locations

The location of the cassandra-topology.properties file depends on the type of installation:

  • Package installations and Installer-Services installations: /etc/dse/cassandra/cassandra-topology.properties

  • Tarball installations and Installer-No Services installations: <installation_location>/resources/cassandra/conf/cassandra-topology.properties

The location of the cassandra.yaml file depends on the type of installation:

  • Package installations and Installer-Services installations: /etc/dse/cassandra/cassandra.yaml

  • Tarball installations and Installer-No Services installations: <installation_location>/resources/cassandra/conf/cassandra.yaml

The location of the dse.yaml file depends on the type of installation:

  • Package installations and Installer-Services installations: /etc/dse/dse.yaml

  • Tarball installations and Installer-No Services installations: <installation_location>/resources/dse/conf/dse.yaml

The location of the cassandra-rackdc.properties depends on the type of installation:

  • Package installations and Installer-Services installations: /etc/dse/cassandra/cassandra-rackdc.properties

  • Tarball installations and Installer-No Services: installation_location/resources/cassandra/conf/cassandra-rackdc.properties

Procedure

Complete the tasks outlined in Initializing a DataStax Enterprise cluster to prepare the environment.

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

  1. Suppose you install DataStax Enterprise (DSE) 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.

    For example, the tokens for a six-node cluster with a single datacenter:

    Node Token

    node0

    0

    node1

    21267647932558653966460912964485513216

    node2

    42535295865117307932921825928971026432

    node3

    63802943797675961899382738893456539648

    node4

    85070591730234615865843651857942052864

    node5

    106338239662793269832304564822427566080

    Or a six-node cluster with two 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 node and clear the data:

    Package installations

    To stop DSE:

    sudo service dse stop

    To remove data from the default directories:

    sudo rm -rf /var/lib/cassandra/*
    Tarball installations

    From the installation location, stop the database:

    bin/dse cassandra-stop

    Remove all data:

    cd /var/lib/cassandra/data &&
sudo rm -rf data/* commitlog/* saved_caches/* hints/*

  5. Configure properties in cassandra.yaml on each new node, following the configuration of the other nodes in the cluster.

    Use the yaml_diff tool to review and make appropriate changes to the cassandra.yaml and dse.yaml configuration files.

    1. Configure node properties.

  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, assign datacenter and rack names to the IP addresses of each node, and assign a default datacenter name and rack name for unknown nodes.

    For migrations from PropertyFileSnitch: The GossipingPropertyFileSnitch always loads cassandra-topology.properties when the file is present. Remove the file from each node on any new cluster or any cluster migrated from the PropertyFileSnitch.

    		 
    # Transactional Node IP=Datacenter:Rack
110.82.155.0=DC_Transactional:RAC1
110.82.155.1=DC_Transactional:RAC1
110.54.125.1=DC_Transactional:RAC2
110.54.125.2=DC_Analytics:RAC1
110.54.155.2=DC_Analytics:RAC2
110.82.155.3=DC_Analytics:RAC1
110.54.125.3=DC_Search:RAC1
110.82.155.4=DC_Search:RAC2

# default for unknown nodes
default=DC1:RAC1

  8. After you have installed and configured DSE on all nodes, start the seed nodes one at a time, and then start the rest of the nodes:

    After making changes to the configuration files, you must restart the nodes for the changes to take effect.

  9. Check that your cluster is up and running:

    dsetool status

    Make sure all nodes are in Up/Normal status:

    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

    If the cluster has problems starting, visit IBM Support.

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