rhsummit-2024

Related content for Garmin's presentations at RedHat Summit 2024

Scaling OpenShift at Garmin: Leveraging Jsonnet, Tekton & ArgoCD

Openshift Commons Gathering

The examples below are designed to offer a quick bootstrap for using Jsonnet to templatize your configuration and automation. See Installing Jsonnet if needed.

Example 1 - Hierarchical Data Structures

Use Jsonnet to render a complete cluster configuration file from multiple hierarchically structured configuration files.

• reduce duplication using object orientation to define cluster data
• minimize the amount of information needed to build a cluster

A few things to notice as you run this example:

• Imports tie each file together with its parent. The bottom-up approach makes adding new clusters very easy.
• Hidden items - any keys with :: after them will be hidden from the output, but are available to Jsonnet during the rendering process
• Late binding / lazy language - fields like self.environments and self.environment aren't declared until the datacenter and cluster files, but are referenced in the all-clusters file.
• Notice the name attribute in the rendered output. When combining multiple objects, the right-most one wins. Both all-clusters and cluster01 have a name attribute.

Configuration Files

• 01-data-hierarchy/all-clusters.libsonnet
• 01-data-hierarchy/dc1/datacenter.libsonnet
• 01-data-hierarchy/dc1/clusters/cluster01.libsonnet

Rendering Output

Execute Jsonnet against the cluster file to see the rendered results:

• jsonnet -J ./01-data-hierarchy 01-data-hierarchy/dc1/clusters/cluster01.libsonnet

Example 2 - Openshift ConsoleNotification (Banner)

This example builds on the previous example.

• The rendered cluster configuration is passed as a top-level argument to the Jsonnet interpreter.
• The template uses data from the cluster object to populate of the consoleNotification object.
• The rendered output is a kubernetes object; it can be applied manually or via automation to configure the cluster.

Template File

• 02-kube-object/consolenotification.jsonnet

Rendering Output

Execute Jsonnet to see the rendered results:

• jsonnet -y -J ./01-data-hierarchy --tla-code-file cluster="01-data-hierarchy/dc1/clusters/cluster01.libsonnet" 02-kube-object/consolenotification.jsonnet

Jsonnet Rust Implementation

There is a Rust implementation of Jsonnet as well as the de facto Go implementation. If you want to use the rust implementation, use these commands to execute jrsonnet instead of jsonnet.

• jrsonnet -J ./01-data-hierarchy 01-data-hierarchy/dc1/clusters/cluster01.libsonnet
• jrsonnet -y -f json -J ./01-data-hierarchy --tla-code-file cluster="01-data-hierarchy/dc1/clusters/cluster01.libsonnet" 02-kube-object/consolenotification.jsonnet

Links & References

• jsonnet.org
• Jsonnet tutorial - learn most of Jsonnet in an hour or two
• Jsonnet Standard Library Reference - this is where Jsonnet puts the fun in function. :)
• Jsonnet on the Kubernetes Slack - join the #jsonnet channel.
• jrsonnet - Jsonnet Rust implementation
• Installing Jsonnet