Tuesday, 16 July 2019

Weblogic under Kubernetes: the weblogic topology of the future

Already 4 months ago I attended the PaaSForum 2019 in Mallorca. As every year it was great to meet members of the big EMEA Oracle Partner family.

And of course a lot of interesting talks and workshops. This year I was especially interested in announcements around SOA Suite and Project Helidon as a Microservice framework. But certainly also Weblogic under Kubernetes.
And actually, to me, the Kubernetes Weblogic Operator that was this years most enthusing subject.

With his WebLogic on Kubernetes talk Maciej Gruszka, Director Product Management, enlightened the future Oracle envisions for WebLogic. He started with stating that 'Weblogic is not dead!'. Well, he got me with that already!

The road ahead is making WebLogic fit to run in Docker and managed by Kubernetes. It might not be exactly what I had in mind, but it is certainly great news to learn that WebLogic will be around and alive for a future ahead. Oracle thrives to make future releases of Weblogic available as Docker images.

Today already, WebLogic is fully supported to run in a Docker container. And according to Marciej, the team is busy with the SOA and OSB teams to get those products fit and available for Docker too. It might even be possible that future releases are going to be delivered as a Docker image.

What is the Weblogic Operator?

To run in a Kubernetes managed cluster, Kubernetes needs to be able to perform lifecycle operation on a Weblogic Managed server. For that  the Weblogic Operator for Kubernetes is created and introduced. A Kubernetes Operator is a sort of Adapter on top of a non-Kubernetes system that translates Kubernetes lifecycle commands to operations within the specific application.

The Weblogic Operator  uses Kubernetes API to implement operations like:
  • Provisioning
  • Life cycle maangement
  • Updates
  • Scaling
  • Security
Besides the Weblogic Operator, Oracle also provides an Exporter for Prometheus and Elastic Stack, for monitoring and logging. Since the managed servers are within a container, you'll need to export events and logfiles to have them accessible and introspectible, even when the container is down or recreated from an updated image.

Some interesting links


There are actually two topologies to choose from:
  • Domain within the Docker Image
  • Domain on a Persistent Volume
With the first one the container is actually stateless. All it needs to know is within the container. The Admin Console can be used for diagnostic and monitoring purposes, but not for updating the domain. Because spinning a new container will have it read the domain from the internal container image.

With the persistent volume topology the domain is stored outside the container. Changes are persisted. This topology is more in line with an On Premises installation of Weblogic. However, High Availability and Disaster Recovery is limited, because Persistent Volume needs to be shared and the domain configuration needs to be synced across datacenters. With 'In Image' Domains, things get simpler, because the domain is transported within the container. Downside is that changes in the domain require creating a new image through the CI/CD pipeline.

Most customers seem to choose for the 'Domain in Image' topology. In practice, domains don't change that much.

You can  adapt specific artifacts like data source connections, urls and username/passwords using Configuration Overrides.


At the PaaSForum we got the chance to play around with Kubernetes and Weblogic. The workshop is described here: https://github.com/nagypeter/weblogic-operator-tutorial. You should fork this to a repository with your own Github account, because it contains the files and scripts to create an image, the tutorial works you through configuring Oracle Container Pipelines (Worker) and for that it needs a Github repo.

There is a Domain In Image variant and  a persistent volume variant of the tutorial.

Steps to follow for the Domain In Image variant

  1. Setup Oracle Kubernetes Engine instance on Oracle Cloud Infrastructure. You'll need a trial accound on cloud.oracle.com. It will then guide you through the setup of an Kubernetes cluster on OCI.
  2. Build WebLogic container image using Oracle Container Pipelines (Wercker). The second time I did the workshop I decided to change all the labels, namespaces and the domain name. Every where there is a reference to 'sample', I entered 'makker'. In this step the image is created from your fork of the github repo. If you change the name of the domain, there are two files to edit:
    1. The Dockerfile.create is called at the initial creation of the image. If there is a base image, the Dockerfile.update is called, to update the image. The Dockerfile.create creates an image with a complete domain, including the application. But the Dockerfile.update only updates the application. So you need to update the Dockerfile.create to change the domain name in the DOMAIN_NAME environment variable in the top of the file. 
    2. The Dockerfile.create copies the scripts folder into the image. That folder contains a wlst script, called model.py. At the top, a variable domain_name is declared with the same domain name assigned to it.
    If you do not change it, and want rename the domain to start it with a different name using Kubernetes later on, then you need to remove the image from the image repository, and then run the Oracle Container Pipelines-pipeline again.
  3.  Install WebLogic Operator: installs the Weblogic Operator.
  4.  Install and configure Traefik: this installs a Traefik loadbalancer on your environment. It will loadbalance over your Weblogic managed servers.
  5. Deploy WebLogic domain: this step lets you prepare your Kubernetes cluster to run the Weblogic domain. Reuse the same domain name as explained in step 2.
  6. Scaling WebLogic cluster: This one I found particularly cool. In this step you update the domain resource yaml file, to update the number of managed servers in the domain. After that, automagically a new Kubernetes pod is spawned that starts a new Managed Server. By the way, the domain will have a dynamic cluster with predefined Managed Servers based on Server Templates.
  7. Override domain configuration:  this will show you how to perform domain configuration overrides to update the datasource.
  8. Update the appliation: The whole point of this exercise is to show you how to setup a CI/CD chain that when you update your application, the image is updated and the domain can be restarted through Kubernetes, with the new image.
  9. Assing the Weblogic Pods to specific nodes or licenced nodes. The latter is important because Weblogic is licensed, so you can't just run it on any number of nodes.
The tutorial is quite elaborate and descriptive. If you stick to the naming, it will guide you through the proces ending up with a running environment. The fun is in being self-wise and choose your own naming. That's how I tripped at step 5  Deploy Weblogic Domain. I could have stuck with the given name. But I didn't feel like it, it was more fun to understand where it was used. Now you can take advantage of it.


I refrained discussing why you would want to run Weblogic under Docker. I have thoughts and had discussions about it. However, it made me enthousiastic that this way Weblogic can be taken with us into the containerized future.

For me the next things to explore are:
  • Create a database on another OCI image, and create a new domain, with a sample application that actually uses that database. It would be fun to create an actuall application on it.
  • Try the same with a persistent volume. A few months ago I was busy with creating java classes to start Kafka. The goal was to create Weblogic Startup classes to have Kafka started at startup of a Weblogic server. Now, it may not seem logical to you, but wouldn't it be great to combine the two and have Kafka embedded in a Weblogic cluster on a Kubernetes Cluster? Well, at least it seems fun to me. Since Kafka needs to log it's messages in a persistent log, we need to do this with a Persistent Volume.
  • Check out other topologies and related technologies. Like accessing the logs. I really would like to be able to  inspect the Weblogic log files within the container.
Have fun with the tutorial.