Add Reserve Nodes to Existing Deployment

This procedure describes how to add nodes to an existing deployment and define them as reserve nodes.

Before continuing, read the introduction in Add Reserve Nodes.

Prerequisites

  • A new Exasol 8 deployment

  • The parameter CCC_HOST_CLEANUP must be set to false in the configuration that was used to create the deployment. If you created the deployment with CCC_HOST_CLEANUP=true, you will not be able to add nodes using this method.

Setting the config path

When you make changes to an existing deployment you must run use the same configuration that was used when creating the deployment. Unless that configuration is in the current working directory (on the host where you run c4), you must prepend the c4 commands with the path to the configuration using CCC_CONFIG=<path-to-config>. For example:

CCC_CONFIG=./path_to_config/my_config c4 <command>

In the following examples, the default configuration file config is used.

Procedure

The following procedures use the c4 and confd_client command-line tools in a Linux terminal. For more information about these tools, see Exasol Deployment Tool (c4)Exasol Deployment Tool (c4)Exasol Deployment Tool (c4)Exasol Deployment Tool (c4) and ConfD.

Step 1: Prepare the hosts

Prepare the new host machines according to the hardware, network, and operating system requirements described in System Requirements.

To enable parallel IMPORT and EXPORT operations, the nodes must have consecutive and evenly spaced static IPv4 addresses in the same subnet.

Step 2: Reserve the nodes in the configuration

On a jump host that has SSH access to the cluster, run the c4 command c4 host reserve <PLAY_ID>. Add the following parameters as environment variables before the command:

Parameter Description
CCC_CONFIG

Path to the configuration file that was used when creating the deployment.

CCC_HOST_RESERVED_ADDRS

List of private IP addresses of the hosts to be reserved, separated by spaces.
CCC_HOST_RESERVED_EXTERNAL_ADDRS

List of public IP addresses of the hosts to be reserved, separated by spaces.

This parameter is only required if the existing data nodes were deployed with public IP addresses (if CCC_HOST_EXTERNAL_ADDRS was set at deploy time).

  • For more details about how to use environment variables in c4 commands, see Parameters in c4.

  • To find the PLAY_ID of the deployment, use c4 ps.

Example:
CCC_CONFIG=config c4 ps
      
      N  PLAY_ID   NODE  MEDIUM  INSTANCE     EXTERNAL_IP     INTERNAL_IP  STAGE  STATE      UPTIME    TTL
  ┌─  1  3a4a7d8d  11    host    c5d.2xlarge  203.0.113.11    10.0.0.11    d      running    04:35:16  +∞
  │   1  3a4a7d8d  12    host    c5d.2xlarge  203.0.113.12    10.0.0.12    d      running    04:35:16  +∞
  │   1  3a4a7d8d  13    host    c5d.2xlarge  203.0.113.13    10.0.0.13    d      running    04:35:16  +∞
  └─  1  3a4a7d8d  14    host    c5d.2xlarge  203.0.113.14    10.0.0.14    d      running    04:35:16  +∞
CCC_CONFIG=config CCC_HOST_RESERVED_ADDRS="10.0.0.15 10.0.0.16" CCC_HOST_RESERVED_EXTERNAL_ADDRS="203.0.113.15 203.0.113.16" c4 host reserve 3a4a7d8d
INFO[2024-06-18 08:53:46] Reserving new nodes for deployment: ****************************
INFO[2024-06-18 08:53:49] Done

The c4 host reserve command will overwrite any previously reserved IP addresses in CCC_HOST_RESERVED_ADDRS and CCC_HOST_RESERVED_EXTERNAL_ADDRS in the configuration file.

Step 3: Connect to COS

Connect to EXAClusterOS (COS) on the cluster using c4 connect -t <DEPLOYMENT>[.<NODE>]/cos. For example:

c4 connect -t 1.11/cos

If you do not specify a node, c4 will connect to the first active node in the deployment.

For more information about how to use c4 connect, see How to use c4.

The following examples use ConfD through the command-line tool confd_client, which is available on all database nodes. You can also access ConfD through XML-RPC in your own Python programs. For more information, see ConfD.

Placeholder values are indicated with UPPERCASE characters. Replace the placeholders with your own values.

Step 4: Add the nodes to the deployment

To add the nodes to the deployment, use the ConfD job infra_instances_add with the following parameters:

Parameter name Data type Description
nid integer ID of an existing node. The configuration of this node will be cloned to create the new nodes.
num_nodes integer The number of nodes that you want to create.
Example:

This example adds two nodes by cloning the node with ID 11.

confd_client infra_instances_add nid: 11 num_nodes: 2

The added nodes will automatically start up and reach deployment stage c (COS service running, database not running). At this point the nodes are not yet part of the cluster.

Step 5: Add the nodes to the cluster

To add the new nodes to the cluster as reserve nodes, use the ConfD job db_add_reserve_nodes with the following parameters:

Parameter Name Data type Description
db_name string The name of the database
node_list list List of node IDs (integers) to add as reserve nodes
Example:
confd_client db_add_reserve_nodes db_name: MY_DATABASE node_list: '[15, 16]'

Step 6: Verify that the nodes are added

To verify that the nodes have been added, use the ConfD job node_list. 

confd_client node_list