A three-node cluster with Apache Kafka

Last update: July 28 2026

Apache Kafka is a distributed software message broker for real-time data stream processing from The Apache Software Foundation. The broker allows you to collect, store, and process large volumes of data from various sources and transfer them to data processing and analysis systems. Apache Kafka uses a three-node distributed cluster architecture for fault tolerance.

You can create a three-node cluster with a pre-installed Apache Kafka application. In Russia, the cluster nodes run on a cloud server with the SelectOS 1 64-bit operating system. In other countries — Ubuntu 24.04.

Before creating a cloud server with an application, review the software license agreements included in the image.

Minimum resource requirements

	Test environment	Production environment
Number of vCPUs	4	8
RAM	8 GB	32 GB
Boot volume	16 GB	from 16 GB *

* The boot volume size for a production environment depends on your needs.

Create a three-node cluster with Apache Kafka

In Selectel, to create a cluster, you must first create a temporary cloud server with Apache Kafka. Creating a temporary server initiates the creation of a three-node cluster. Each node is a cloud server with the configuration chosen when creating the temporary cloud server.

The name of each server in the cluster will be in the format cs-<server_name>-<cluster_number>, where <server_name> is the server name and <cluster_number> is the server number in the cluster from 1 to 3.

The three created cloud servers are in the same subnet as the temporary cloud server.

Next, a Kafka cluster will be configured on three cloud servers. If the cluster is configured successfully, the temporary cloud server is deleted. If the temporary cloud server was not deleted, there was a problem during the Kafka cluster configuration. To identify the problem, view the logs.

The cost of the cluster will be calculated based on the cost of three cloud servers.For more information about the cloud platform payment model, see the Payment model and prices article.

To configure Apache Kafka, you must specify user data during creation — custom configuration parameters used for connecting to the OpenStack API.

1. Create a service user.

2. Create a public floating IP address.

3. Create a cloud server with Apache Kafka.

1. Create a service user

Create a service user, select the member or reader role in the permissions and Projects as the access scope. Users can be created by the Account Owner or users with the iam.admin role.

2. Create a public floating IP address

Create a public floating IP address so the cloud server with Zabbix is accessible from the internet.

Use the Create a public floating IP address section of the Public floating IP addresses guide.

3. Create a cloud server with Apache Kafka

1. In the control panel, on the top menu, click Products and select Cloud Servers.

2. Click Create server.

3. Fill in the blocks:

   • Name and placement;
   • Source;
   • Configuration;
   • Volumes;
   • Internet;
   • Private network;
   • Security;
   • Access;
   • Additional settings.

4. Check the cloud server price. Note that after configuration, the price for a three-node cluster will be calculated using the formula: cloud server price * 3.

5. Click Create.

Name and placement

1. Enter the server name. It will be set as the hostname in the operating system.

2. Select a location where the server will be created. The available server configurations and resource costs depend on the location. You cannot change the location after the server is created.

Source

1. Open the Applications tab.

2. Select Cloud Kafka.

3. Optional: if you need a different current or archived application version, select it in the Version field.

Configuration

Choose a configuration with at least 2 vCPUs and at least 8 GB of RAM if the server is intended for development and testing. If the server is intended for moderate workloads in a production environment, choose a configuration with at least 8 vCPUs and at least 32 GB of RAM. The boot disk size for a production environment depends on your needs.

For all lines, except Shared and Dedicated, two types of server configurations are available:

• fixed configurations — configurations of lines with different specifications, in which the resource ratio is fixed;
• custom configurations — configurations in which you can specify any resource ratio.

Different processors are used in the configurations, depending on the line and pool segment. You can customize the selected configuration. After the server is created, you will be able to change the configuration.

Fixed configuration

1. Open the tab with the line.

2. Click Fixed.

3. Optional: you can adjust the configuration if you are creating a server in the ru-6 multi-zone pool or in the ru-3b, ru-7a, and ru-7b pool segments:

   3.1. Expand the block with the configuration settings description.

   3.2. Optional: select the processor vendor. Vendor selection is not available in all pools.

   3.3. Optional: if you do not want physical processor cores reserved for the cloud server vCPUs, uncheck the Dedicated cores checkbox. For more information, see the Dedicated cores instructions.

   3.4. Optional: if you want to disable Hyper-Threading for a server with dedicated cores, uncheck the Hyper-Threading (SMT) checkbox.

   3.5. Optional: if you are creating a server with dedicated cores and want to host a multiprocessor server on a single NUMA node, select the Mandatory placement on a single NUMA node checkbox. You can host a server with 4 vCPUs or more on one NUMA node. If the cloud server resources cannot be placed on one node, the server will not be created. For more information, see the Placement on a single NUMA node subsection of the Dedicated cores instructions.

4. Select a configuration.

5. If both local and network volumes are available in the selected configuration, select the volume to be used as the boot volume:

   • local volume — check the Local SSD NVMe volume checkbox. A server with a local volume can only be created from images and applications;
   • network volume — do not check the Local SSD NVMe disk checkbox.

   The amount of RAM allocated to the server may be less than specified in the configuration — the operating system kernel reserves a portion of RAM depending on the kernel version and distribution. You can check the allocated amount on the server using the sudo dmesg | grep Memory command.

Custom configuration

1. Open the tab with the line.

2. Click Custom.

3. Optional: you can adjust the configuration if you are creating a server in the ru-6 multi-zone pool or in the ru-3b, ru-7a, and ru-7b pool segments:

   3.1. Expand the block with the configuration settings description.

   3.2. Optional: select the processor vendor. Vendor selection is not available in all pools.

   3.3. Optional: if you do not want physical processor cores reserved for the cloud server vCPUs, uncheck the Dedicated cores checkbox. For more information, see the Dedicated cores instructions.

   3.4. Optional: if you want to disable Hyper-Threading for a cloud server with dedicated cores, uncheck the Hyper-Threading (SMT) checkbox.

   3.5. Optional: if you are creating a cloud server with dedicated cores and want to host a multiprocessor server on a single NUMA node, select the Mandatory placement on a single NUMA node checkbox. You can host a cloud server with 4 vCPUs or more on one NUMA node. If the cloud server resources cannot be placed on one node, the server will not be created. For more information, see the Placement on a single NUMA node subsection of the Dedicated cores instructions.

4. Specify the number of vCPUs.

5. Specify the RAM size.

6. If you need to add graphics processors to the server, click Add GPU, select the GPU type, and specify the number of GPUs. The selected line will change to the GPU line. If you selected an image without GPU optimization in the Source block and the Auto-select GPU image toggle is on, the selected image will automatically change to a GPU-optimized image.

7. If both local and network volumes are available in the selected configuration, select the volume to be used as the boot volume:

   • local volume — check the Local SSD NVMe volume checkbox. A server with a local volume can only be created from images and applications;
   • network volume — do not check the Local SSD NVMe disk checkbox.

   The amount of RAM allocated to the server may be less than specified in the configuration — the operating system kernel reserves a portion of RAM depending on the kernel version and distribution. You can check the allocated amount on the server using the sudo dmesg | grep Memory command.

Volumes

1. If you did not check the Local SSD NVMe disk checkbox when configuring, the first specified network volume will be used as the server boot disk. To configure it:

   1.1. Select the network boot volume type.

   1.2. Specify the network boot volume size in GB or TB. Take into account the maximum size limits for network volumes.

   1.3. If you chose the Universal v2 or SSD Fast v2 disk type, specify the total number of read and write operations in IOPS. After creating the disk, you can change the number of IOPS — increase or decrease. You can change IOPS an unlimited number of times.

2. Optional: add an additional server network volume:

   2.1. Click Add.

   2.2. Select the network volume type.

   2.3. Specify the network volume size in GB or TB. Take into account the maximum size limits for network volumes.

   2.4. If you selected the Universal v2 or Fast SSD v2 volume type, specify the total IOPS for read and write operations. After the volume is created, you can change the IOPS value — increase or decrease it. There is no limit to the number of IOPS changes.

   After the server is created, you will be able to attach new additional volumes.

Internet

Configure public access to the server.

The cloud server will be added to a private subnet that is connected to a cloud router with 1:1 NAT and internet access. Access to and from the internet will be through the cloud router. The server will be accessible from the internet via a public floating IP address.

1. In the Internet access field, select the Public floating IP address access type.

2. Select the public floating IP address you created in step 2.

Private network

The cloud server can be added to an existing or new private subnet.

Existing private subnet

1. In the Subnet field, select a private subnet.

2. Optional: in the IP address field, change the default IP address.

3. In the Router field, select an existing router or create a new one.

   If the router is not connected to the internet, it will be automatically connected after the server is created.

New private subnet

1. In the Subnet field, select New private subnet.

2. In the Network field, select an existing network or create a new one.

3. Optional: change the subnet CIDR.

4. Optional: in the IP address field, change the default IP address.

5. In the Router field, select an existing router or create a new one.

   If the router is not connected to the internet, it will be automatically connected after the server is created.

Security

Select security groups to filter traffic on server ports. Without security groups, all traffic is denied. If this block is missing, traffic filtering (port security) is disabled in the server network. With filtering disabled, all traffic is permitted.

Access

1. Place an SSH key for the project on the server for secure connection:

   1.1. If an SSH key for the project has not been added to the cloud platform, click Add SSH key, enter the key name, paste the public key in OpenSSH format, and click Add.

   1.2. If a project SSH key has been added to the cloud platform, select an existing key in the SSH key field. The SSH key is available only in the pool where it is hosted.

2. Optional: in the Password for root field:

   2.1. Copy the password for the root user—a user with unrestricted privileges for any system action.

   2.2. Save the password in a secure place and do not share it in plain text.

Additional settings

1. Optional: if you plan to create multiple servers and want to increase infrastructure reliability, add the server to a placement group:

   1.1. To create a new group, click Create in the Placement group field.

   1.2. Select New group and enter the group name.

   1.3. Select the placement policy for different hosts:

   • preferred — soft-anti-affinity. The system will try to place servers on different hosts. If there is no suitable host when creating the server, it will be created on the same host;
   • mandatory — anti-affinity. Servers in the group must be placed on different hosts. If there is no suitable host when creating the server, the server will not be created.

   1.4. If the group has been created, select the required placement group in the Placement group field.

2. Optional: to add additional information or filter servers in the list, add server tags. OS and configuration tags are added automatically. To add a new tag, enter it in the Tags field.

3. To add a script to be executed by the cloud-init agent on the first boot of the operating system, in the Automation block, in the User data field:

   • open the Text tab and paste the script as text;
   • or open the File tab and upload the script file.

   #cloud-config
   
   write_files:
   - path: "/opt/gomplate/values/user-values.yaml"
     permissions: "0644"
     content: |
       ServiceUsername: <username>
       ServicePassword: <password>
       ProjectId: <project_id>
       CloudRegion: <pool>
       CloudZone: <pool_segment>
       AccountNumber: <account_id>

   Specify:

   • <username> — service user name. You can view it in the control panel: in the top menu, click IAM and go to the Service Users section (this section is only available to the account owner and users with the iam.admin role);
   • <password> — service user password. You can view it when creating the user or change it to a new one.
   • <project_id> — project ID. You can copy it in the control panel: in the top menu, click Products → Cloud Servers → open the projects menu → in the project line, click ;
   • <pool> — the pool where the cloud server will be created, for example, ru-3;
   • <pool_segment> — the pool segment where the cloud server will be created, for example, ru-3b;
   • <account_id> — account number in the control panel. You can view it in the control panel in the top right corner.

View logs

If the temporary cloud server was not deleted, an issue occurred during the Apache Kafka cluster configuration. For example, the service user may have insufficient permissions, a wrong password was entered, or the user data settings contain errors.

1. Connect to the server that you created earlier.

2. To view the error log, open the cloud-init-output.log file in the vi text editor.

   vi /var/log/cloud-init-output.log

3. Depending on the error log, grant access to the service user or change the user data settings.

4. Recreate the server.

5. If you cannot fix the issue yourself, create a ticket and attach the logs with errors.