How to build a high-availability cluster in RedHat Fuse 7.x on Karaf?

Question

RedHat Fuse 7.x is offered both on OpenShift and Karaf. While OpenShift version supports containerization of RedHat Fuse application, it inherently makes it highly available I believe. But I am wondering if load balanced and highly available cluster can be formed for RedHat Fuse Karaf version. Earlier till version 6.x, they used to support Fuse Fabric for clustering. The documentation of version 7.x says they have discontinued Fuse Fabric support. If anyone has deployed RedHat Fuse on Karaf in a clustered environment, please let me know how it was achieved.

Answer 1

For my understanding Red Hat Fuse on karaf is just Red Hat supported version of Karaf with bunch of Red Hat Flavored features installed like Camel and Hawtio. OpenShift and Apache Karaf offer two very different levels of containerization. one could say you use OpenShift to run microservices and Apache karaf to run nanoservices.

While you can install and run multiple applications inside Apache Karaf they're still running on the same virtual machine and operating system. You can however create docker image and run Apache karaf on container(s) in Docker, Kubernetes, OpenShift etc like any other application.

This can be useful if you want to group bunch of applications/services together to save resources, share dependencies or just to reduce the amount of different docker containers or deployments.

There's official docker image available for Apache Karaf one can use for reference to create docker image(s) for Red hat fuse on Karaf.

• Apache karaf docker - DockerHub
• Apache karaf docker - Github

Generally you probably want to create image from a custom karaf assemply that includes all the features and bundles you need to run your applications so when things get added updated you can just swap the image.

Technically you could also use CD/CI pipelines or something like Karaf Cellar to manage multiple karaf instances. This would allow you to add, remove and update functionality of karaf instance even while its running. This however sounds quite complex to pull off and maintain.

As a disclaimer I would like to add that I've not used Apache Karaf or Red Hat Fuse on Karaf with Kubernetes or OpenShift yet. Most of my experience is with running karaf using docker/podman compose or RHEL VM.