<a id="ansible-scale"></a>

# Scale Confluent Platform Clusters using Ansible

<a id="ansible-scale-up"></a>

## Scale up Confluent Platform

Ansible Playbooks for Confluent Platform supports scaling up Confluent clusters. This use-case scenario
demonstrates how to scale up Kafka, ksqlDB, and Connect using Ansible
playbooks.

1. The below example `hosts.yaml` file configures:
   * 3 KRaft nodes
   * 3 Kafka broker nodes
   * 2 ksqlDB clusters, named `ksql1` and `ksql2`, with each cluster having 1
     node
   * 2 Connect clusters, named `elastic` and `syslog`, with each cluster
     having 1 node
   * 1 Control Center node

   ```yaml
   kafka_controller:
     hosts:
       ec2-34-219-110-48.us-west-2.compute.amazonaws.com:
       ec2-18-237-72-224.us-west-2.compute.amazonaws.com:
       ec2-35-161-39-212.us-west-2.compute.amazonaws.com:

   kafka_broker:
     hosts:
       ec2-34-219-110-48.us-west-2.compute.amazonaws.com:
       ec2-34-211-33-32.us-west-2.compute.amazonaws.com:
       ec2-35-89-77-112.us-west-2.compute.amazonaws.com:

   ksql:
     children:
       ksql1:
       ksql2:

   ksql1:
     vars:
       ksql_service_id: ksql1_
     hosts:
       ec2-34-219-110-48.us-west-2.compute.amazonaws.com:

   ksql2:
     vars:
       ksql_service_id: ksql2_
     hosts:
       ec2-35-89-77-112.us-west-2.compute.amazonaws.com:

   kafka_connect:
     children:
       syslog:
       elastic:

   syslog:
     vars:
       kafka_connect_group_id: connect_syslog
     hosts:
       ec2-35-89-77-112.us-west-2.compute.amazonaws.com:

   elastic:
     vars:
       kafka_connect_group_id: connect-elastic
     hosts:
       ec2-35-89-77-112.us-west-2.compute.amazonaws.com:

   control_center_next_gen:
     hosts:
       ec2-35-163-80-4.us-west-2.compute.amazonaws.com:
   ```
2. Update the `hosts.yaml` file to scale up the clusters:
   ```yaml
   kafka_controller:
     hosts:
       ec2-34-219-110-48.us-west-2.compute.amazonaws.com:
       ec2-34-211-33-32.us-west-2.compute.amazonaws.com:
       ec2-35-89-77-112.us-west-2.compute.amazonaws.com:

   kafka_broker:
     hosts:
       ec2-34-219-110-48.us-west-2.compute.amazonaws.com:
       ec2-34-211-33-32.us-west-2.compute.amazonaws.com:
       ec2-35-89-77-112.us-west-2.compute.amazonaws.com:
       ec2-35-89-77-113.us-west-2.compute.amazonaws.com:--- [1]
       ec2-35-89-77-114.us-west-2.compute.amazonaws.com:--- [2]

   ksql:
     children:
       ksql1:
       ksql2:

   ksql1:
     vars:
       ksql_service_id: ksql1_
     hosts:
       ec2-34-219-110-48.us-west-2.compute.amazonaws.com:
       ec2-35-89-77-116.us-west-2.compute.amazonaws.com:--- [3]

   ksql2:
     vars:
       ksql_service_id: ksql2_
     hosts:
       ec2-34-219-110-48.us-west-2.compute.amazonaws.com:
       ec2-34-219-110-50.us-west-2.compute.amazonaws.com:--- [4]

   kafka_connect:
     children:
       syslog:
       elastic:

   syslog:
     vars:
       kafka_connect_group_id: connect_syslog
     hosts:
       ec2-35-89-77-112.us-west-2.compute.amazonaws.com:

   elastic:
     vars:
       kafka_connect_group_id: connect-elastic
     hosts:
       ec2-35-89-77-112.us-west-2.compute.amazonaws.com:
       ec2-35-89-77-113.us-west-2.compute.amazonaws.com:--- [5]

   control_center_next_gen:
     hosts:
       ec2-35-163-80-4.us-west-2.compute.amazonaws.com:
   ```

   * [1] [2] Add 2 new nodes to the Kafka broker cluster.
   * [3] Add 1 new node to the `ksql1` ksqlDB cluster.
   * [4] Add 1 new node to the `ksql2` ksqlDB cluster.
   * [5] Add 1 new node to the `elastic` Connect cluster.
3. Re-run the playbook to scale up the clusters:
   ```bash
   ansible-playbook -i hosts.yml confluent.platform.all
   ```

   The clusters are scaled up with:
   * 5 Kafka broker nodes (scaled up)
   * 2 ksqlDB clusters, `ksql1` and `ksql2` with 2 nodes each (scaled up)
   * The `syslog` Connect cluster with 1 node
   * The `elastic` Connect cluster with 2 nodes (scaled up)
   * 1 Control Center node
4. To distribute existing loads to new nodes, make sure that you enable the
   Self-Balancing feature using the Ansible [custom properties](ansible-configure.md#ansible-custom-properties). For the list of configuration options, see
   [Self-Balancing Configurations on the Brokers](https://docs.confluent.io/platform/current/kafka/sbc/configuration_options.html#sbc-configurations-on-the-brokers).