stack-knative

A Crossplane Configuration package that deploys Knative Serving, Knative Eventing, and optional NATS JetStream on any Kubernetes cluster with Istio.

Overview

stack-knative installs and configures a complete serverless platform:

• Knative Operator — manages the lifecycle of Knative components via Helm
• Knative Serving — autoscaling serverless workloads with Istio ingress, scale-to-zero, and revision management
• Knative Eventing — event-driven architecture with pluggable channels and brokers
• NATS JetStream (optional, enabled by default) — high-performance messaging backend for Knative Eventing channels

The stack assumes Istio is already installed (e.g. via stack-istio) and configures Knative to use Istio for ingress, mTLS, and network policies.

Deletion protection (Usages) ensures correct teardown order: Serving/Eventing CRs are deleted before the Knative Operator that provides their CRDs.

Prerequisites

• Crossplane installed in the cluster
• Istio installed (provides security.istio.io CRDs and ingress)
• Crossplane providers:
  • provider-helm (>=v1)
  • provider-kubernetes (>=v1)
• Crossplane function:
  • function-auto-ready (>=v0.6.0)

Quick Start

apiVersion: pkg.crossplane.io/v1
kind: Configuration
metadata:
  name: stack-knative
spec:
  package: ghcr.io/hops-ops/stack-knative:latest

apiVersion: stacks.hops.ops.com.ai/v1alpha1
kind: Knative
metadata:
  name: knative
  namespace: default
spec:
  clusterName: default

This minimal spec installs the Knative Operator, Knative Serving (with Istio ingress), Knative Eventing (with NATS channels), and a 3-node NATS JetStream cluster.

The Journey

Stage 1: Getting Started

Minimal configuration — everything uses sensible defaults. Serving and Eventing are both enabled, NATS provides the default channel backend, and Istio handles ingress.

apiVersion: stacks.hops.ops.com.ai/v1alpha1
kind: Knative
metadata:
  name: knative
  namespace: default
spec:
  clusterName: default

What you get:

• Knative Serving with Istio ingress, pod affinity/tolerations/topology spread enabled
• Knative Eventing with NATS JetStream as the default channel
• Revision garbage collection (max 10 non-active, retain 48h since creation)
• Istio mTLS permissive mode on the knative-serving namespace

Stage 2: Production with TLS and Custom Domain

Add a hosted zone and cert-manager for automatic TLS on Knative services.

apiVersion: stacks.hops.ops.com.ai/v1alpha1
kind: Knative
metadata:
  name: knative
  namespace: default
spec:
  clusterName: production-cluster
  hostedZone: example.com
  certManager:
    enabled: true
  labels:
    team: platform

What this adds:

• All Knative services get *.example.com domain routing
• cert-manager automatically provisions TLS certificates via Let's Encrypt
• External domain TLS enabled on the Serving network config

Stage 3: Customized Components

Override Helm values and Knative specs for specific requirements.

apiVersion: stacks.hops.ops.com.ai/v1alpha1
kind: Knative
metadata:
  name: knative
  namespace: default
spec:
  clusterName: production-cluster
  hostedZone: example.com
  certManager:
    enabled: true
  knativeServing:
    spec:
      config:
        gc:
          max-non-active-revisions: "20"
          retain-since-last-active-time: "48h"
  knativeEventing:
    spec:
      config:
        features:
          new-apiserversource-filters: enabled
  nats:
    values:
      config:
        jetstream:
          fileStore:
            pvc:
              size: 50Gi

Serving or Eventing Only

Disable components you don't need:

spec:
  clusterName: my-cluster
  knativeEventing:
    enabled: false
  nats:
    enabled: false

Composed Resources

Resource	Kind	Purpose
knative-operator	Helm Release	Installs the Knative Operator (manages Serving/Eventing CRDs)
namespace-knative-serving	Object (Namespace)	Creates the knative-serving namespace with istio-injection: enabled
namespace-knative-eventing	Object (Namespace)	Creates the knative-eventing namespace with istio-injection: enabled
knative-serving	Object (KnativeServing)	Deploys Knative Serving via the operator
knative-serving-peer-auth	Object (PeerAuthentication)	Sets Istio mTLS to permissive in knative-serving namespace
knative-eventing	Object (KnativeEventing)	Deploys Knative Eventing via the operator
nats	Helm Release	Installs NATS JetStream cluster (3 replicas, 10Gi storage)
usage-knative-serving	Usage	Prevents operator deletion before KnativeServing cleanup
usage-knative-eventing	Usage	Prevents operator deletion before KnativeEventing cleanup

Spec Reference

Field	Type	Default	Description
clusterName	string	required	Target cluster name, used for provider config defaults
hostedZone	string		DNS zone for Knative service domains (e.g. example.com)
certManager.enabled	bool	false	Enable cert-manager TLS integration
certManager.issuerRef	string	letsencrypt-production	ClusterIssuer reference
labels	map	{}	Labels merged with defaults on all resources
managementPolicies	string[]	["*"]	Crossplane management policies
helmProviderConfigRef.name	string	<clusterName>	Helm ProviderConfig name
helmProviderConfigRef.kind	string	ProviderConfig	ProviderConfig or ClusterProviderConfig
kubernetesProviderConfigRef.name	string	<clusterName>	Kubernetes ProviderConfig name
kubernetesProviderConfigRef.kind	string	ProviderConfig	ProviderConfig or ClusterProviderConfig
knativeOperator.name	string	knative-operator	Helm release name
knativeOperator.namespace	string	knative-operator	Namespace
knativeOperator.values	object	{}	Helm values merged with defaults
knativeOperator.overrideAllValues	object		Replaces all defaults
knativeServing.enabled	bool	true	Install Knative Serving
knativeServing.name	string	knative-serving	KnativeServing resource name
knativeServing.namespace	string	knative-serving	Namespace
knativeServing.spec	object	(see defaults)	Spec merged with defaults
knativeServing.overrideAllSpec	object		Replaces all spec defaults
knativeEventing.enabled	bool	true	Install Knative Eventing
knativeEventing.name	string	knative-eventing	KnativeEventing resource name
knativeEventing.namespace	string	knative-eventing	Namespace
knativeEventing.spec	object	(see defaults)	Spec merged with defaults
knativeEventing.overrideAllSpec	object		Replaces all spec defaults
nats.enabled	bool	true	Install NATS JetStream
nats.name	string	nats	Helm release name
nats.namespace	string	nats	Namespace
nats.values	object	{}	Helm values merged with defaults
nats.overrideAllValues	object		Replaces all defaults

Serving Defaults

When not overridden, Knative Serving is configured with:

• Ingress: Istio (istio.ingress.networking.knative.dev)
• Pod features: affinity, securityContext, nodeSelector, tolerations, topologySpreadConstraints
• GC: max 10 non-active revisions, retain 48h since creation, 15h since last active
• TLS: enabled when certManager.enabled: true
• Domain: configured when hostedZone is set

Eventing Defaults

When not overridden, Knative Eventing is configured with:

• Istio integration: enabled
• Default channel: NATS JetStream (when nats.enabled: true)

Status

Field	Type	Description
status.ready	bool	Overall readiness (all components healthy)

Development

make render        # Render all examples
make validate      # Validate against XRD schema
make test          # Run unit tests
make e2e           # Run E2E tests