Goal

The Denodo Platform can be containerized to be run in a container platform such as Docker. The usage of containers eases the adoption of modern architectures, for instance, microservices, which can be orchestrated with Kubernetes.

This document explains how to deploy Denodo containers using Kubernetes.

Content

Kubernetes is an orchestration system for containers, it allows the IT teams not only to manage the deployment of containerized applications but also to scale deployments by increasing the number of replicas for the deployment. Kubernetes allows also to perform other actions, for instance, to update the current containers with its new version released.

This document will make use of the Kubernetes command-line tool (kubectl) that interacts with the Kubernetes cluster via the Kubernetes API. This article assumes that Kubernetes and Docker are already installed and working in your local environment and that Kubernetes is enabled on Docker, as this enables a single-node cluster when Docker is started. It is also recommended to follow the Denodo Platform Container QuickStart Guide as a prerequisite for this article, as it serves to check that the Denodo container is working successfully in the Docker installation. The Denodo users that are new to Kubernetes can also check the Kubernetes Basics tutorial to learn the basic concepts and usage of Kubernetes. The “kubectl” command-line tool that communicates with Kubernetes to execute commands in the cluster.

The Denodo Platform 8.0 introduced a new RMI implementation which eases the network configuration of the Virtual DataPort servers, requiring only one single port for establishing the connection with the Virtual DataPort Administration Tool and JDBC clients, but for JMX connections it still needs the two standard RMI Registry and RMI Factory ports. Due to these configuration differences between Denodo 8.0 and Denodo 7.0, we are providing one YAML file per version.

The following YAML configuration file defines a Kubernetes Service and Deployment that will deploy the Denodo Platform 8.0 container generated by Denodo  in the Kubernetes cluster:

denodo-services.yaml for Denodo 8.0

The following YAML configuration file defines a similar Kubernetes Service and Deployment than the previous one but for a Denodo Platform 7.0 container:

denodo-services.yaml for Denodo 7.0

If you are using your own custom Denodo containers, you need to change both the “command:” and “agrs:” lines in the previous YAML files to match the requirements from your containers.

To create both elements, service, and deployment, in the Kubernetes environment save the script to a file and name it to something like denodo_service.yaml. Then, execute the following Kubernetes command in a console:

> kubectl create -f denodo_service.yaml

Execution of the denodo-service.yaml

Although this article does not try to explain how Kubernetes works or how YAML files are created, it is interesting to outline the following from the YAML file definition:

• The service for Denodo 8.0 exposes five ports: 8999, 8997, 8996, 8995 and 8090. These are the ports published in the service that are mapped to ports in the container. This mapping allows the use of the port 9090 in the container but publishes it as 8090 in the service. This is also done with other ports, however, the RMI factory port, in the example 8995, has to be the same in both the Pod and the Service because due to the internal workings of RMI connections this port cannot be mapped. If the RMI factory port has to be changed, it must be done at the Pod level (with appropriate container options).
• The configuration of the YAML file is assuming that a standalone license (like evaluation or denodo express licenses) is used and available locally, so the host license file C:/Denodo/Licenses/denodo_8_0.lic is mapped to the container /opt/denodo/denodo.lic file to be used as the Pod license file. Please update the host path to point to your actual license file or read the following sections for instructions on how to use a Solution Manager licensing.
• All the Denodo pods will share the hostname denodo-hostname, as this is the selected solution to configure RMI appropriately with the standard Denodo container. The RMI configuration will be made automatically by the startup script that is included in the container using the hostname. Notice that the field hostname cannot include dots, but If needed, Kubernetes also provides a subdomain field so you can assign a FQDN to the pod.

After the Service deployment is completed, it will be possible to connect to the new Denodo instance from a Virtual DataPort client such as the Virtual DataPort Administration Tool with the following URL:

//denodo-hostname:8999/admin

In addition, notice that for using denodo-hostname as the connection host in your client computers, it will be necessary that the client computer is able to resolve that hostname to the IP address of the denodo-service, either by defining the denodo-hostname in the DNS server or in the hosts file of the client computer. Please, ensure that you have network connectivity from the client computer to the Kubernetes Service, by configuring the network routes appropriately.

Connecting to the Virtual DataPort Server within the Kubernetes cluster

The following command will provide all the information required regarding the Kubernetes Service that is deployed:

kubectl describe denodo-service output

Finally, in case that it is needed to clean the environment, the following command can be executed to delete the Denodo service deployed in Kubernetes.

> kubectl delete -f denodo-service.yaml

Kubernetes and CPUs

By default, the pods running in Kubernetes are able to view as available all the cores from the node where the pod is running. If you are using a Denodo license with core restrictions, you might find that a server cannot start because the cores available in the pod exceeds the license restriction.

You can check the number of cores in your nodes with the following command:

In the case that you can not adjust the capacity of the nodes in your cluster, the KB Article How to limit the number of CPUs in Kubernetes explains how to reconfigure your nodes to allow you to limit the number of cores por a pod in Kubernetes, so you can start Denodo in nodes that have more cores than those allowed by the license.

Licenses Managed by a Denodo Solution Manager

The Denodo Solution Manager helps large organizations to manage the Denodo licensing in an easy way, for instance, it can serve licenses to the servers running on Kubernetes. However, due to the containers and Kubernetes architecture, we will not use it for deploying new revisions directly on running containers, instead, we will follow the Kubernetes best practices by creating new images and updating the deployments accordingly. If desired, the Solution Manager features around revisions can still be used to generate these images from non containerized environments.

In order to get the license from the Solution Manager, we need to apply some changes to the pod configuration. The script provided above to create the Kubernetes deployment makes use of a standalone license. However, it is possible to apply some changes to it in order to retrieve the license information from a License Server instead of pointing to a license file. To do this, just make the following replacements in the script file:

Replace the last part of the file:

with

The Solution Manager configuration file SolutionManager.properties should point to the Solution Manager server, with a configuration like the one shown here:

The hostname solutionmanager-hostname points to the Solution Manager server and it has to be resolved by the pods. Also, in the Solution Manager side, it will be required to create the Kubernetes environment with the Virtual DataPort servers setting the Host parameter as denodo-hostname.

References

Denodo Platform Container QuickStart Guide

Kubernetes Documentation

Learn Kubernetes Basics

Kubernetes on Docker