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01: Health Checks and Resource Status

In a declarative system, how do we know if the actual state of the world matches our desired state? This is the fundamental question of observability in a GitOps workflow.

Both Crossplane and ArgoCD provide rich status information that we can use to monitor the health of our system.

ArgoCD Health Checks

As we discussed in the "GitOps Fundamentals" section, ArgoCD uses Lua scripts to determine the health of a resource. A resource can be in one of the following states:

  • Healthy: The resource is in its desired state.
  • Progressing: The resource is in the process of being created or updated.
  • Degraded: The resource has failed to reach its desired state.
  • Suspended: The resource is intentionally not being reconciled.
  • Missing: The resource is defined in Git but is not present in the cluster.
  • Unknown: The health of the resource could not be determined.

We have already configured custom health checks for our Crossplane resources, so the ArgoCD UI gives us a real-time, at-a-glance view of the health of our entire infrastructure stack.

Crossplane Resource Status

Crossplane itself provides detailed status conditions on all its resources (Claims, CompositeResources, and ManagedResources).

You can inspect the status of any Crossplane resource using kubectl.

Example: Checking the status of a MySQLInstance claim.

kubectl get mysqlinstance my-app-db -o yaml

apiVersion: database.example.org/v1alpha1
kind: MySQLInstance
metadata:
  name: my-app-db
# ...
status:
  conditions:
    - type: Ready
      status: "True"
      lastTransitionTime: "2023-10-27T18:30:00Z"
      reason: Available
      message: "The composite resource is available and ready"
    - type: Synced
      status: "True"
      lastTransitionTime: "2023-10-27T18:28:00Z"
      reason: ReconcileSuccess
      message: "Successfully reconciled composite resource"
  connectionDetails:
    lastPublishedTime: "2023-10-27T18:30:01Z"
  # ... other fields

Key fields to watch:

  • status.conditions: This array tells you the current state of the resource. The Ready condition with status: "True" is the most important indicator of health.
  • status.connectionDetails: For claims, this section will be populated with the connection information for the provisioned resource (e.g., database endpoint, username, password secret reference).

The crossplane CLI

The crossplane command-line tool provides some helpful commands for observing the status of your resources.

crossplane trace

The trace command gives you a complete dependency tree for a given claim, showing you the CompositeResource and all the underlying ManagedResources.

crossplane trace mysqlinstance my-app-db

Output:

NAME                                            READY   STATUS    AGE
MySQLInstance/my-app-db                         True    Available 5m
└── CompositeMySQLInstance/my-app-db-xyz123     True    Available 5m
    ├── FlexibleServer/my-app-db-server         True    Available 4m
    └── FirewallRule/my-app-db-fw               True    Available 3m

This is an invaluable tool for debugging. If a claim is not becoming Ready, you can use trace to pinpoint exactly which underlying resource is failing.

By combining the ArgoCD UI with the detailed status information from Crossplane, we can build a comprehensive picture of our system's health.

➡️ Next: Monitoring with Prometheus