The Nimble-Opti-Adapter is a dedicated Kubernetes operator engineered to handle specific use cases. It's targeted towards Kubernetes clusters that have already integrated the Cert-Manager operator and Nginx-Ingress controller, and use Let's Encrypt as their certificate authority for acquiring SSL certificates validated through the `acme.cert-manager.io/http01-edit-in-place: true` annotation in the ingress. Moreover, the ingress requires the `nginx.ingress.kubernetes.io/backend-protocol: HTTPS` annotation to ensure service accessibility. The operator proficiently addresses the issue of auto-renewal of certificates in this scenario, given that the HTTP01 Ingress resolver doesn't align with this setup.

nimble-opti-adapter is a Kubernetes operator that automates certificate renewal management when using ingress with the annotation cert-manager.io/cluster-issuer for services that require TLS communication. This operator is designed to work seamlessly with the NGINX ingress controller, efficiently handling the nginx.ingress.kubernetes.io/backend-protocol: HTTPS annotation.

The operator monitors the creation and modification of both CustomResourceDefinitions (CRDs) of kind NimbleOpti and Ingress resources. The following is a detailed overview of the operator's behavior:

1. 🚫 The operator is currently configured to watch for creation or modification events on NimbleOpti CRDs and ingress.

2. 🚦 Upon Ingress resource events, the operator verifies the existence of the nimble.opti.adapter/enabled: "true" label:

   • In the absence of this label, the operator remains passive.
   • If the label is present, it validates the existence of a NimbleOpti CRD within the same namespace.
     • If the CRD is missing, a new NimbleOpti CRD is instantiated with default values.
     • If the CRD already exists, the operator scans for any path in spec.rules[].http.paths[].path containing .well-known/acme-challenge.
       • If found, the certificate renewal process for the Ingress resource is triggered.

3. 📆 The operator runs a daily audit of all Ingress resources with the nimble.opti.adapter/enabled: "true" label and associated NimbleOpti CRD in the same namespace:

   • In the absence of matching resources, no action is taken.
   • If matches are found:
     • If the ingress manifest the presence of .well-known/acme-challenge within the spec.rules[].http.paths[].path attribute, the operator shall initiate the certificate renewal process.
     • The operator fetches the associated Secret referenced in spec.tls[].secretName for each tls[], calculates the remaining time until certificate expiry and checks it against the CertificateRenewalThreshold specified in the NimbleOpti CRD. If the certificate is due to expire within or on the threshold, certificate renewal is initiated.

4. 🔄 The certificate renewal process involves the following steps:

   • The nginx.ingress.kubernetes.io/backend-protocol: HTTPS annotation is temporarily stripped from the Ingress resource.
   • A timer kicks in, waiting for the absence of spec.rules[].http.paths[].path containing .well-known/acme-challenge or for the lapse of the AnnotationRemovalDelay specified in the NimbleOpti CRD.
   • The duration of annotation updates during renewal is captured as nimble-opti-adapter_annotation_updates_duration_seconds and dispatched to a Prometheus endpoint.
   • The nginx.ingress.kubernetes.io/backend-protocol: HTTPS annotation is reinstated on the Ingress resource.
   • If the .well-known/acme-challenge is not exist then counter nimble-opti-adapter_certificate_renewals_total is incremented and sent to a Prometheus endpoint.

• 🔄 Automatic certificate renewal based on certificate validity and user-defined waiting times
• 🏷️ Supports multi-namespace operation with a configurable label selector
• 📊 Prometheus metrics collection for certificate renewals and annotation updates
• 🚀 Easy installation using Helm
• 🔌 Extensible architecture for future enhancements

• 🔔 Customizable alerting and notification system for certificate renewals and errors
• 🔗 Integration with external certificate issuers or other certificate management systems
• 📈 Enhanced Prometheus metrics for deeper insights into certificate management
• 🚦 Support for other ingress controllers besides NGINX
• 📝 Automatic handling of additional ingress annotations as needed

• Kubernetes cluster (v1.16+)
• Helm (v3+)
• Cert-Manager operator
• Ingress NGINX Controller

This configuration assumes you are working from a Linux Shell or macOS.

git clone https://github.com/uri-tech/nimble-opti-adapter.git
cd nimble-opti-adapter

make manifests # Generate WebhookConfiguration, ClusterRole and CustomResourceDefinition objects.
make install # Install CRDs into the K8s cluster specified in ~/.kube/config.
make deploy IMG=nimbleopti/nimble-opti-adapter:latest # Deploy controller to the K8s cluster specified in ~/.kube/config.

helm install nimble-opti-adapter ./helm/nimble-opti-adapterconfig

To modify the operator, edit the Helm chart templates or values.yaml file in the helm/nimble-opti-adapterconfig directory.

Repackage the Helm chart and upgrade the release with the following commands:

cd nimble-opti-adapter/helm/
helm package nimble-opti-adapterconfig
helm upgrade nimble-opti-adapter ./nimble-opti-adapterconfig-0.1.0.tgz

Edit the values.yaml file in the helm/nimble-opti-adapterconfig directory to customize the following parameters:

• labelSelector: The label selector for namespaces the operator will manage certificates in (default: nimble.opti.adapter/enabled: 'true')
• certificateRenewalThreshold: The waiting time (in days) before the certificate expires to trigger renewal
• annotationRemovalDelay: The delay (in seconds) after removing the nginx.ingress.kubernetes.io/backend-protocol: HTTPS annotation before re-adding it

Label the Ingress where the operator should manage certificates:

apiVersion: v1
kind: Ingress
metadata:
  name: your-target-ingress
  labels:
    nimble.opti.adapter/enabled: "true"

Create a nimble-opti-adapter custom resource in any namespace:

apiVersion: adapter.uri-tech.github.io/v1
kind: NimbleOpti
metadata:
  name: default
spec:
  certificateRenewalThreshold: 30
  annotationRemovalDelay: 10

nimble-opti-adapter exposes the following Prometheus metrics:

• nimble-opti-adapter_certificate_renewals_total: Total number of certificate renewals
• nimble-opti-adapter_annotation_updates_duration_seconds: Duration (in seconds) of annotation updates during each renewal

We welcome contributions to the nimble-opti-adapter project! Please see the CONTRIBUTING.md file for more information on how to contribute.

nimble-opti-adapter is licensed under the Apache License, Version 2.0.

For any questions, bug reports, or feature requests, please open an issue on our GitHub repository.