cloudschedulersource

README

Cloud Scheduler Source

This repository implements an Event Source for (Knative Eventing)[http://github.com/knative/eventing] defined with a CustomResourceDefinition (CRD). This Event Source represents (Google Cloud Scheduler)[https://cloud.google.com/scheduler/]. Point is to demonstrate an Event Source that does not live in the (Knative Eventing Sources)[http://github.com/knative/eventing-sources] that can be independently maintained, deployed and so forth.

This particular example demonstrates how to perform basic operations such as:

• Create a Cloud Scheduler Job when a Source is created
• Delete a Job when that Source is deleted
• Update a Job when the Source spec changes

Details

Actual implementation contacts the Cloud Scheduler API and creates a Job as specified in the CloudSechedulerSource CRD Spec. Upon success a Knative service is created to receive calls from the Cloud Scheduler and will then forward them to the Channel.

Purpose

Provide an Event Source that allows subscribing to Cloud Scheduler and processing them in Knative.

Another purpose is to serve as an example of how to build an Event Source using a (Kubernetes Sample Controller)[https://github.com/kubernetes/sample-controller] as a starting point.

Installation

gcloud services enable 

1. Create GCP Service Account(s). You can either create one with both permissions or two different ones for least privilege. If you create only one, then use the permissions for the Source's Service Account (which is a superset of the Receive Adapter's permission) and provide the same key in both secrets.

   • The Source's Service Account.

     1. Determine the Service Account to use, or create a new one.

     2. Give that Service Account the 'Pub/Sub Editor' role on your GCP project.

     3. Download a new JSON private key for that Service Account.

     4. Create a secret for the downloaded key:

        kubectl -n knative-sources create secret generic cloudscheduler-source-key --from-file=key.json=PATH_TO_KEY_FILE.json
        

   • Note that you can change the secret's name and the secret's key, but will need to modify some things later on.

Running

1. Setup Knative serving or
2. Setup Knative eventing

Prerequisite: Since the sample-controller uses apps/v1 deployments, the Kubernetes cluster version should be greater than 1.9.

# assumes you have a working kubeconfig, not required if operating in-cluster
$ go build -o sample-controller .
$ ./sample-controller -kubeconfig=$HOME/.kube/config

# create a CustomResourceDefinition
$ kubectl create -f artifacts/examples/crd.yaml

# create a custom resource of type Foo
$ kubectl create -f artifacts/examples/example-foo.yaml

# check deployments created through the custom resource
$ kubectl get deployments

Example

The CRD in crd-status-subresource.yaml enables the /status subresource for custom resources. This means that UpdateStatus can be used by the controller to update only the status part of the custom resource.

To understand why only the status part of the custom resource should be updated, please refer to the Kubernetes API conventions.

In the above steps, use crd-status-subresource.yaml to create the CRD:

# create a CustomResourceDefinition supporting the status subresource
$ kubectl create -f artifacts/examples/crd-status-subresource.yaml

Cleanup

You can clean up the created CustomResourceDefinition with:

$ kubectl delete crd foos.samplecontroller.k8s.io