Charmed Knative Operators

Knative is a Kubernetes-based platform to deploy and manage modern serverless workloads.

For more details of what is possible with Knative, see https://knative.dev/

Usage

Pre-requisites

Microk8s 1.21/stable

NOTE: These instructions assume you have run microk8s enable dns storage rbac metallb:"10.64.140.43-10.64.140.49,192.168.0.105-192.168.0.111"

Add a model and set variables

MODEL_NAME="knative"
DEFAULT_GATEWAY="knative-gateway"
juju add-model ${MODEL_NAME}

Deploy dependencies

Knative (in particular knative-serving) requires istio-operators to be deployed in the model. To correctly configure them, you can:

ISTIO_CHANNEL=1.11/stable
juju deploy istio-pilot --config default-gateway=${DEFAULT_GATEWAY} --channel ${ISTIO_CHANNEL} --trust
juju deploy istio-gateway istio-ingressgateway --config kind="ingress" --channel ${ISTIO_CHANNEL} --trust
juju relate istio-pilot istio-ingressgateway

`knative-operator`

The knative-operator is responsible for installing, configuring, and managing the serving and eventing components. You must deploy the charmed knative-operator before any other Knative component.

KNATIVE_CHANNEL=1.1/edge
juju deploy knative-operator --trust --channel ${KNATIVE_CHANNEL}

`knative-serving`

knative-serving provides components that enable rapid deployment of serverless containers, autoscaling (including down to zero), support for multiple layers, and revision tracking. Charmed knative-serving can be deployed as follows:

juju deploy knative-serving --config namespace="knative-serving" --config istio.gateway.namespace=${MODEL_NAME} --config istio.gateway.name=${DEFAULT_GATEWAY} --channel ${KNATIVE_CHANNEL} --trust

where:

namespace: The namespace knative-serving resources will be deployed into (it cannot be deployed into the same namespace as knative-operator or knative-eventing
istio.gateway.namespace: The namespace the Istio gateway is deployed to (generally, the model that Istio is deployed to).
istio.gateway.name: The name of the Istio gateway

`knative-eventing`

knative-eventing provides tools for routing events from producers to sinks, enabling developers to use an event-driven architecture with their applications. Charmed knative-eventing can be deployed as follows:

juju deploy knative-eventing --config namespace="knative-eventing" --channel ${KNATIVE_CHANNEL} --trust

where:

namespace: The namespace knative-eventing resources will be deployed into (it cannot be deployed into the same namespace as knative-operator or knative-serving

Collecting metrics

Metrics are collected by an OpenTelemetry collector managed by the knative-operator, which is then scraped by prometheus-k8s. Please follow these instructions to enable metrics collection for knative-eventing and knative-serving.

Deploy prometheus-k8s and relate to knative-operator

juju deploy prometheus-k8s --trust
juju relate prometheus-k8s:metrics-endpoint knative-operator:metrics-endpoint

Enable metric collection for knative-<eventing/serving>

juju relate knative-<eventing/serving>:otel-collector knative-operator:otel-collector

Wait for everything to be active and idle
You can now access the Prometheus dashboard to have access to the collected metrics. Alternatively, you could send GET requests to the OpenTelemetry metrics exporter directly using the otel-export Service, for example:

curl <otel-exporter service>:8889/metrics

Please refer to Collecting Metrics in Knative for more information.

Integration example

To run a simple example that integrates both eventing and serving, you can run the one provided in examples/.

NOTE: this example is based on Using a Knative Service as a source

Create the cloudevents-player Knative Service

kubectl apply -f examples/cloudevents-player.yaml

Get the LOADBALANCER_IP

LOADBALANCER_IP=$(kubectl get svc istio-ingressgateway-workload -n${MODEL_NAME} -o jsonpath='{.status.loadBalancer.ingress[0].ip}')

Send an event

curl -i http://cloudevents-player.default.${LOADBALANCER_IP}.nip.io
    -H "Content-Type: application/json"
    -H "Ce-Id: 123456789"
    -H "Ce-Specversion: 1.0"
    -H "Ce-Type: some-type"
    -H "Ce-Source: command-line"
    -d '{"msg":"Hello CloudEvents!"}'

Expected output:

HTTP/1.1 202 Accepted
content-length: 0
date: Mon, 27 Jun 2022 19:05:02 GMT
x-envoy-upstream-service-time: 5
server: istio-envoy

View events

curl http://cloudevents-player.default.${LOADBALANCER_IP}.nip.io