Set up Operational Rules

You can set up operational rules in the AppConfiguration model with the opsrule accessory and corresponding platform configurations in the workspace directory. The opsrule is the collection of operational rule requirements for the application that are used as a preemptive measure to police and stop any unwanted changes.

Prerequisites

Please refer to the prerequisites in the guide for deploying an application.

The example below also requires you to have initialized the project using the kusion workspace create and kusion init command, which will create a workspace and also generate a kcl.mod file under the stack directory.

Managing Workspace Configuration

In the first guide in this series, we introduced a step to initialize a workspace with an empty configuration. The same empty configuration will still work in this guide, no changes are required there.

However, if you (or the platform team) would like to set default values for the opsrule to standardize the behavior of applications, you can do so by updating the ~/dev.yaml. Note that the platform engineers should set the default workload to Kusion Operation CollaSet and installed the Kusion Operation controllers properly, the opsrules module will generate a PodTransitionRule instead of updating the maxUnavailable value in the deployment:

modules:
  service:
    default:
      type: CollaSet
  kusionstack/opsrule@0.1.0:
    default:
      maxUnavailable: 30%

Please note that the maxUnavailable in the workspace configuration only works as a default value and will be overridden by the value set in the application configuration.

The workspace configuration need to be updated with the command:

kusion workspace update dev -f ~/dev.yaml

Example

Add the opsrule module dependency to kcl.mod:

[package]
name = "simple-service"
version = "0.1.0"

[dependencies]
kam = { git = "https://github.com/KusionStack/kam.git", tag = "0.1.0" }
network = { oci = "oci://ghcr.io/kusionstack/network", tag = "0.1.0" }
opsrule = { oci = "oci://ghcr.io/kusionstack/opsrule", tag = "0.1.0" }

[profile]
entries = ["main.k"]

Add the opsrule snippet to the AppConfiguration in simple-service/dev/main.k:

import kam.v1.app_configuration as ac
import kam.v1.workload as wl
import kam.v1.workload.container as c
import opsrule

helloworld: ac.AppConfiguration {
    workload: wl.Service {
        ...
    }
    # Configure the maxUnavailable rule
    accessories: {
        "opsrule": opsrule.OpsRule {
            "maxUnavailable": 50%
        }
    }
}

Applying

Re-run steps in Applying, resource scaling is completed.

Validation

We can verify the application deployment strategy now has the updated attributes maxUnavailable: 50% in the container configuration.