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Deploy a High Available Cluster Using Eloqctl

Previously, we covered how to deploy a single node EloqSQL cluster using eloqctl. In this document, we will focus on deploying a highly available cluster.

1. Prerequisites​

Please ensure you've reviewed the following document:

2. Deploy Eloqctl on the control machine​

For step-by-step guidance, please check out the previous document:

3. Initialize the cluster topology file​

Example cluster topology files can be found in the .eloqctl/config/examples/ directory.

To deploy a highly available cluster, use eloqsql_cassandra.yaml as the default configuration template.

# example yaml file
.eloqctl/config/examples/eloqsql_cassandra.yaml

To enable high availability, edit the eloqsql_cassandra.yaml file. High availability is achieved through two key configurations:

  1. The log cluster must be distributed and replicated.
  2. The Cassandra cluster must be distributed and replicated.
connection:
  username: "${USER}"
  auth_type: "keypair"
  auth:
    keypair: "/home/${USER}/.ssh/id_rsa"
deployment:
  cluster_name: "eloqsql-cluster"
  product: "EloqSQL"
  version: "latest"
  install_dir: "/home/${USER}"
  tx_service:
    tx_host_ports: [10.0.0.1:6379, 10.0.0.2:6379, 10.0.0.3:6379]
  log_service:
    nodes:
      - host: 10.0.0.1
        port: 9000
        data_dir:
          - "/home/${USER}/eloqsql-cluster/wal_EloqSql"
      - host: 10.0.0.2
        port: 9000
        data_dir:
          - "/home/${USER}/eloqsql-cluster/wal_EloqSql"
      - host: 10.0.0.3
        port: 9000
        data_dir:
          - "/home/${USER}/eloqsql-cluster/wal_EloqSql"
    replica: 3
  storage_service:
    cassandra:
      host: [10.0.0.4, 10.0.0.5, 10.0.0.6]
      kind: !Internal
        mirror: "https://download.eloqdata.com"
        version: "4.1.3"
  monitor:
    data_dir: ""
    eloq_metrics:
      path: "/eloq_metrics"
      port: 18081
    prometheus:
      download_url: "https://github.com/prometheus/prometheus/releases/download/v2.42.0/prometheus-2.42.0.linux-amd64.tar.gz"
      port: 9500
      host: 10.0.0.7
    grafana:
      download_url: "https://dl.grafana.com/oss/release/grafana-9.3.6.linux-amd64.tar.gz"
      port: 3301
      host: 10.0.0.7
    node_exporter:
      url: "https://github.com/prometheus/node_exporter/releases/download/v1.5.0/node_exporter-1.5.0.linux-amd64.tar.gz"
      port: 9200
    cassandra_collector:
      mcac_agent: "https://github.com/datastax/metric-collector-for-apache-cassandra/releases/download/v0.3.4/datastax-mcac-agent-0.3.4-4.1-beta1.tar.gz"
      mcac_port: 9103

For detailed explanations for each configuration option in the YAML file, please refer to the previous document Deploy Single Node Cluster. In this document, we will focus specifically on the high availability aspects of the configuration file.

  • tx_service.tx_host_ports:
    Type: List of Strings
    The transaction cluster is deployed across three nodes: 10.0.0.1:6379, 10.0.0.2:6379, and 10.0.0.3:6379. Data is sharded among these nodes, with each node responsible for a portion of the data. If one node fails, the remaining nodes will take over the data from the failed node and continue to serve client requests seamlessly.

  • log_service.nodes:
    Type: Composite
    Here, we specify three nodes for the log service cluster, which are co-located with the transaction cluster. Alternatively, you can deploy the log service on separate machines if preferred.

  • log_service.replica:
    Type: Integer
    Set the number of replicas for the log service to 3. This ensures that each WAL log record is replicated across three log nodes. With this setup, the logs will be preserved even in the event of a node failure or disk crash.

  • storage_service.cassandra.host:
    Type: List of Strings
    When deploying EloqSQL with Cassandra as the persistent storage engine, the compute and storage components are fully decoupled. In this example, Cassandra is deployed on three separate machines: 10.0.0.4, 10.0.0.5, and 10.0.0.6.

  • monitor
    Prometheus and grafana are installed on a separate host at 10.0.0.7.

5. Run the deployment command​

After you modified the eloqsql_cassandra.yaml. Use the eloqctl launch command to provision an EloqSQL cluster

eloqctl launch ${HOME}/.eloqctl/config/examples/eloqsql_cassandra.yaml -s

The command will installed the EloqSQL componnets in the specified cluster.

If you see the following message, the EloqSQL cluster has been successfully provisioned:

Launch cluster finished, Enjoy!

Feel free to use /home/eloq/eloqsql-cluster/EloqSQL/bin/mariadb or any other Mariadb/Mysql client to connect to EloqSQL and enjoy exploring its features.