Replace Node
This section explains how to replace a failed node in an on-premises installation.
This procedure is carried out using ConfD and Exasol Deployment Tool (c4).
Prerequisites
The database must be stopped.
Procedure
The following examples use ConfD through the command-line tool confd_client, which is available on all database nodes.
Placeholder values are indicated with UPPERCASE characters. Replace the placeholders with your own values.
Step 1: Connect to COS
Connect to EXAClusterOS (COS) on the cluster using c4 connect -t <DEPLOYMENT>[.<NODE>]/cos
. For example:
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.
Step 2: Stop the database
If the database is running, stop it now using the ConfD job db_stop:
Step 3: Prepare the new nodes
Prepare the new node and assign it exactly the same IP addresses that belonged to the failed node. For information about the system requirements for the new node, see System Requirements.
Step 4: Update the configuration
In the same configuration file that you used for the initial deployment, add the IP addresses of the node that will be replaced in a new c4 config parameter CCC_HOST_SETUP_ADDRS
.
For example, with the following configuration only the node with IP address 10.10.10.12
will be replaced:
CCC_HOST_ADDRS="10.10.10.11 10.10.10.12 10.10.10.13"
CCC_HOST_SETUP_ADDRS=10.10.10.12
CCC_HOST_IMAGE_USER=exasol
CCC_HOST_IMAGE_PASSWORD=exasol123
CCC_HOST_KEY_PAIR_FILE=id_rsa
CCC_HOST_DATADISK=/dev/nvme2n1,/dev/nvme3n1
CCC_PLAY_WORKING_COPY=@exasol-8.27.0
The IP addresses that you specify in CCC_HOST_SETUP_ADDRS
must be the same as the failed nodes, and must be present in either CCC_HOST_ADDRS
or CCC_HOST_EXTERNAL_ADDRS
.
The value in CCC_PLAY_WORKING_COPY
must be exactly the same as the currently installed
Exasol package. If you have updated Exasol, make sure that the value corresponds to the package used in the latest update.
Step 5: Deploy the nodes
To deploy the replaced nodes, use c4 host play -i CONFIG_FILE
with the updated configuration file. For example:
or:
You can monitor the deployment using c4 ps
to verify that the nodes start up. For more information, see Install Exasol 8.
Step 6: Start the database
Start the database using the ConfD job db_start: