Resource Health

Overview

Argo CD provides built-in health assessment for several standard Kubernetes types, which is then surfaced to the overall Application health status as a whole. The following checks are made for specific types of kubernetes resources:

Deployment, ReplicaSet, StatefulSet DaemonSet

• Observed generation is equal to desired generation.
• Number of updated replicas equals the number of desired replicas.

Service

• If service type is of type LoadBalancer, the status.loadBalancer.ingress list is non-empty, with at least one value for hostname or IP.

Ingress

• The status.loadBalancer.ingress list is non-empty, with at least one value for hostname or IP.

PersistentVolumeClaim

• The status.phase is Bound

Custom Health Checks

Argo CD supports custom health checks written in Lua. This is useful if you:

• Are affected by known issues where your Ingress or StatefulSet resources are stuck in Progressing state because of bug in your resource controller.
• Have a custom resource for which Argo CD does not have a built-in health check.

There are two ways to configure a custom health check. The next two sections describe those ways.

Way 1. Define a Custom Health Check in argocd-cm ConfigMap

Custom health checks can be defined in resource.customizations field of argocd-cm. Following example demonstrates a health check for cert-manager.io/Certificate.

data:
  resource.customizations: |
    cert-manager.io/Certificate:
      health.lua: |
        hs = {}
        if obj.status ~= nil then
          if obj.status.conditions ~= nil then
            for i, condition in ipairs(obj.status.conditions) do
              if condition.type == "Ready" and condition.status == "False" then
                hs.status = "Degraded"
                hs.message = condition.message
                return hs
              end
              if condition.type == "Ready" and condition.status == "True" then
                hs.status = "Healthy"
                hs.message = condition.message
                return hs
              end
            end
          end
        end
        hs.status = "Progressing"
        hs.message = "Waiting for certificate"
        return hs

The obj is a global variable which contains the resource. The script must return an object with status and optional message field.

NOTE: as a security measure you don’t have access to most of the standard Lua libraries.

Way 2. Contribute a Custom Health Check

A health check can be bundled into Argo CD. Custom health check scripts are located in the resource_customizations directory of https://github.com/argoproj/argo-cd. This must have the following directory structure:

argo-cd
|-- resource_customizations
|    |-- your.crd.group.io               # CRD group
|    |    |-- MyKind                     # Resource kind
|    |    |    |-- health.lua            # Health check
|    |    |    |-- health_test.yaml      # Test inputs and expected results
|    |    |    +-- testdata              # Directory with test resource YAML definitions

Each health check must have tests defined in health_test.yaml file. The health_test.yaml is a YAML file with the following structure:

tests:
- healthStatus:
    status: ExpectedStatus
    message: Expected message
  inputPath: testdata/test-resource-definition.yaml

The PR#1139 is an example of Cert Manager CRDs custom health check.