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Event-Driven Automation with Project Harbor and Knative

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/img/harbor-webhook-function-cover.png

Webhooks everywhere

Webhooks are very popular today. In a nutshell, webhooks are nothing but HTTP servers accepting HTTP requests. These requests are typically events. An event is an immutable fact of something that has happened. Therefore, events are normally written in past tense. Most webhooks accept JSON-encoded events.

Harbor is a prominent open-source container registry. If you never heard of this project, check out my other posts (#harbor). Luckily, Harbor also supports the webhook standard.

Let’s take the example of someone deleting an image from the registry. Harbor generates the following DELETE_ARTIFACT event:

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// Harbor specific JSON payload

{
  "type": "DELETE_ARTIFACT",
  "occur_at": 1655887039,
  "operator": "admin",
  "event_data": {
    "resources": [
      {
        "digest": "sha256:3b465cbcadf7d437fc70c3b6aa2c93603a7eef0a3f5f1e861d91f303e4aabdee",
        "tag": "v2.2.2",
        "resource_url": "harbor-app.jarvis.tanzu/veba-test/veba-image:v1.0"
      }
    ],
    "repository": {
      "name": "veba-image",
      "namespace": "veba-test",
      "repo_full_name": "veba-test/veba-image",
      "repo_type": "public"
    }
  }
}

Source: Harbor Documentation

Events like the above are related to a specific Harbor project.

Harbor project

A project in Harbor contains all repositories of an application. Images cannot be pushed to Harbor before a project is created. Role-Based Access Control (RBAC) is applied to projects, so that only users with the appropriate roles can perform certain operations.

Source: Harbor Documentation

Let’s stick with the example provided. The events sent are very detailed and thus useful. They can be used for ChatOps for example. This is where I came up with the idea to forward the Harbor event to a notification function running on the VMware Event Broker Appliance - VEBA.

VEBA Generic Webhook Endpoint and Webhook Functions

VEBA supports a generic webhook endpoint since version v0.7.0. The webhook endpoint can be enabled during the OVA deployment and is available on https://<veba-fqdn>/webhook afterwards. It accepts incoming CloudEvents as payload.

The challenge is, and William tackled it in THIS POST, that not every solution supports the CloudEvents specification.

Although the idea behind CloudEvents is simple and powerful. If there’s no default description/definition for event data, event handling logics have to be developed again and again!

I hope this will change …

Session from the tweet: “Thinking Cloud Native, CloudEvents Future - Scott Nichols, Chainguard” at KubeCon 2022 Europe 👇 Resources.

For my specific use case with Harbor, I checked the open issue’s on Github to see if someone had already raised the idea of adopting CloudEvents.

Luckily, issue #10146 brings the idea up. Give it a 👍 😉

However, in a brainstorming session with Michael, I got him hooked and he wrote a complete new webhook function which transforms the incoming Harbor events into CloudEvents 💥.

The Use Case with Harbor

The overall idea is to send the non-CloudEvent payload to the new kn-go-harbor-webhook function, get it transformed into a CloudEvent and have the new kn-ps-harbor-slack function triggered.

For the used example above, the new event type will be com.vmware.harbor.delete_artifact.v0.

The following diagram depicts the end-to-end flow of the deployment.

Low hanging Fruits

🍒 = Existing VEBA Function Examples

In order to not only have a “transformation” function available but also a function which will be triggered on a new Harbor specific event, I simply took the existing Slack-Function example, adjusted the necessary fields whithin the handler.ps1 accordingly in order to ultimately pick the wanted data from the incoming event.

Voilà, kn-ps-harbor-slack is ready to serve.

Deploying the new Harbor Functions

Let me guide you through the necessary steps in order to:

  1. have a properly prepared and configured environment (DNS, VEBA, Harbor) available
  2. have the kn-go-harbor-webhook function deployed
  3. have the kn-ps-harbor-slack function deployed

DNS Wildcard Configuration for VEBA

The first required step is to configure your DNS server with a wildcard entry for VEBA. This is necessary because when you’re going to deploy functions to VEBA, they’ll ultimately run as Pods on Kubernetes, or in Knative terminology as Knative Services (serving.knative.dev/service).

Those Services are providing endpoints for which we have to make sure that they are reachable over the wire.

It is presented as follows: https://[function-name].[function-namespace].[veba-fqdn].

Since we are talking about Kubernetes Custom Resources, we can interact with such using kubectl. In order to e.g. check your functions, run kubectl -n vmware-functions get ksvc.

I’m using the Knative CLI for it because it’ll add an additional column to the output which is CONDITIONS. It’s always good to check those.

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kn service list -n vmware-functions

NAME                   URL                                                                  LATEST                       AGE    CONDITIONS   READY   REASON
kn-go-harbor-webhook   http://kn-go-harbor-webhook.vmware-functions.veba-dev.jarvis.tanzu   kn-go-harbor-webhook-00001   9d     3 OK / 3     True
kn-pcli-nsx-tag-sync   http://kn-pcli-nsx-tag-sync.vmware-functions.veba-dev.jarvis.tanzu   kn-pcli-nsx-tag-sync-00001   13d    3 OK / 3     True
kn-pcli-tag            http://kn-pcli-tag.vmware-functions.veba-dev.jarvis.tanzu            kn-pcli-tag-00001            133d   3 OK / 3     True
kn-ps-harbor-slack     http://kn-ps-harbor-slack.vmware-functions.veba-dev.jarvis.tanzu     kn-ps-harbor-slack-00001     9d     3 OK / 3     True

Configuring a DNS wildcard entry on a Windows Server is made easy. Open the DNS Manager, right-click on your Forward Lookup Zone and select New Host (A or AAA). For Name enter *.<VEBA-Hostname>. This should automatically create a FQDN like *.veba-dev.jarvis.tanzu in my example. Last is the IP address of your VEBA.

/img/posts/202207_harbor_webhhok_post/rguske-post-harbor-webhook-function-1.png
Figure I: Windows Server Wildcard DNS Configuration

William is explaining the necessary configurations on his blog when using Unbound on Ubuntu - LINK.

Deploy the kn-go-harbor-webhook Function

Deploying functions on VEBA is simple. Well documented guidance for each specific example function is available on .

If necessary, the first step is in most cases the creation of a Kubernetes secret in order to store sensible data (user credentials, etc.). Having said, we are going to create a new secret called webhook-auth for our function in order to enforce basic authentication on the HTTP endpoint.

Create the webhook-auth secret

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kubectl create secret generic webhook-auth \
--type=kubernetes.io/basic-auth \
--from-literal=username='webhookuser' \
--from-literal=password='replaceme' \
--namespace vmware-functions

Checking the secret to see if the given values have been passed.

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kubectl -n vmware-functions get secret webhook-auth -o yaml
apiVersion: v1
data:
  password: cmVwbGFjZW1l
  username: d2ViaG9va3VzZXI=
kind: Secret
metadata:
  creationTimestamp: "2022-07-04T14:05:49Z"
  name: webhook-auth
  namespace: vmware-functions
  resourceVersion: "291669370"
  uid: c0fc6ecc-a6cb-4532-813b-daea79dc0604
type: kubernetes.io/basic-auth

Let’s quickly decrypt the value for password:

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echo cmVwbGFjZW1l | base64 -d

replaceme

Compliant 👍

Create a SinkBinding

A Knative SinkBinding decouples the event producer ("subject", i.e. kn-go-harbor-webhook) from the receiver ("sink", i.e. VEBA broker). With the following SinkBinding, Knative injects the address of the VEBA broker to the function.

Create the SinkBinding:

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kubectl -n vmware-functions create -f - <<EOF
apiVersion: sources.knative.dev/v1
kind: SinkBinding
metadata:
  name: kn-go-harbor-webhook-binding
spec:
  subject:
    apiVersion: serving.knative.dev/v1
    kind: Service
    name: kn-go-harbor-webhook
  sink:
    ref:
      apiVersion: eventing.knative.dev/v1
      kind: Broker
      name: default
EOF

When checking the deployed object by executing kubectl -n vmware-functions get sinkbinding, you’ll probably notice the info REASON: SubjectMissing. This is normal since it is waiting for the actual function deployment.

Deploy the kn-go-harbor-webhook function

The final step now is the deployment of the kn-go-harbor-webhook function itself.

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kubectl -n vmware-functions create -f - <<EOF
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: kn-go-harbor-webhook
  labels:
    app: veba-ui
spec:
  template:
    metadata:
      annotations:
        autoscaling.knative.dev/maxScale: "1"
        autoscaling.knative.dev/minScale: "1"
    spec:
      containers:
        - image: us.gcr.io/daisy-284300/veba/kn-go-harbor-webhook:1.0
          imagePullPolicy: IfNotPresent
          env:
            - name: ADDRESS
              value: "0.0.0.0"
            - name: WEBHOOK_PATH
              value: "/webhook" # default
            - name: DEBUG
              value: "true"
            - name: WEBHOOK_SECRET_PATH # remove this env to disable basic auth
              value: "/var/bindings/webhook"
          volumeMounts: # remove this when not using basic auth
            - name: webhook-auth
              mountPath: "/var/bindings/webhook"
              readOnly: true
      volumes: # remove this when not using basic auth
        - name: webhook-auth
          secret:
            secretName: webhook-auth
EOF

Conditions and state of the deployment can be checked as already described using kubectl or kn.

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# Using kubectl
kubectl -n vmware-functions get ksvc
NAME                   URL                                                                  LATESTCREATED                LATESTREADY                  READY   REASON
kn-go-harbor-webhook   http://kn-go-harbor-webhook.vmware-functions.veba-dev.jarvis.tanzu   kn-go-harbor-webhook-00001   kn-go-harbor-webhook-00001   True

# Using kn
kn -n vmware-functions service list
NAME                   URL                                                                  LATEST                       AGE    CONDITIONS   READY   REASON
kn-go-harbor-webhook   http://kn-go-harbor-webhook.vmware-functions.veba-dev.jarvis.tanzu   kn-go-harbor-webhook-00001   78m    3 OK / 3     True

Also, checking the logs tells you a lot.

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kubectl -n vmware-functions logs kn-go-harbor-webhook-00001-deployment-7d76fbb5fc-qclfv user-container

2022-07-04T14:32:14.599Z        INFO    harbor-webhook  kn-go-harbor-webhook/server.go:95       starting http server    {"commit": "5472048a", "tag": "1.0", "address": "0.0.0.0:8080", "path": "/webhook", "sink": "http://default-broker-ingress.vmware-functions.svc.cluster.local", "basic_auth": true}

Well, everything is in good condition and the function is ready to receive and transform Harbor notification events.

Configure the Webhook Feature in Harbor

In Harbor, open your project and go to Webhooks. Click on + NEW WEBHOOK and configure it to meet your requirements (e.g. in terms of event types). Important is the Endpoint URL as well as the Auth Header.

For Endpoint URL, enter the complete URL ending with /webhook of the recently created kn-go-harbor-webhook function/Knative Service. For me it’s: https://kn-go-harbor-webhook.vmware-functions.veba-dev.jarvis.tanzu/webhook

For Auth Header, enter Basic followed by a whitespace and the base64-encoded value of the <username>:<password> string combination defined in the webhook-auth secret step. Use a Basic Auth Header Generator like e.g. DebugBear.

/img/posts/202207_harbor_webhhok_post/rguske-post-harbor-webhook-function-2.png
Figure II: Webhook Configuration in Harbor

The Webhook config should show up as shown in Firgue III below:

/img/posts/202207_harbor_webhhok_post/rguske-post-harbor-webhook-function-3.png
Figure III: Configured Webhook in Harbor

Verifying the Configuration

Verifying if everything works as expected can be done by e.g. pushing an image to your project (repo) or e.g. deleteing an existing one. For the sake of my example, I deleted an existing image (artifact) and checked the logs of the user-container, which runs inside the kn-ps-harbor-slack-00001-deployment-xxx-xxx pod.

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$ kubectl -n vmware-functions logs kn-go-harbor-webhook-00001-deployment-7d76fbb5fc-qclfv user-container -f

2022-07-04T14:32:14.599Z        INFO    harbor-webhook  kn-go-harbor-webhook/server.go:95       starting http server    {"commit": "5472048a", "tag": "1.0", "address": "0.0.0.0:8080", "path": "/webhook", "sink": "http://default-broker-ingress.vmware-functions.svc.cluster.local", "basic_auth": true}
2022-07-04T15:01:02.406Z        DEBUG   harbor-webhook  kn-go-harbor-webhook/server.go:140      received request        {"commit": "5472048a", "tag": "1.0", "eventID": "f5c27ced-2b6b-45c3-a795-59efc33947b0", "request": "{\"type\":\"DELETE_ARTIFACT\",\"occur_at\":1656946862,\"operator\":\"admin\",\"event_data\":{\"resources\":[{\"digest\":\"sha256:d3890814cc5a7cfc02403435281cdf51adfb6b67e223934d9d6137a4ad364286\",\"tag\":\"1.21.6-debian-10-r117\",\"resource_url\":\"harbor.jarvis.tanzu/veba-webhook/bitnami-nginx:1.21.6-debian-10-r117\"}],\"repository\":{\"name\":\"bitnami-nginx\",\"namespace\":\"veba-webhook\",\"repo_full_name\":\"veba-webhook/bitnami-nginx\",\"repo_type\":\"public\"}}}"}
2022-07-04T15:01:02.412Z        DEBUG   harbor-webhook  kn-go-harbor-webhook/server.go:173      successfully sent cloudevent    {"commit": "5472048a", "tag": "1.0", "eventID": "f5c27ced-2b6b-45c3-a795-59efc33947b0", "event": "Context Attributes,\n  specversion: 1.0\n  type: com.vmware.harbor.delete_artifact.v0\n  source: /kn-go-harbor-webhook\n  subject: admin\n  id: f5c27ced-2b6b-45c3-a795-59efc33947b0\n  time: 2022-07-04T15:01:02Z\n  datacontenttype: application/json\nData,\n  {\n    \"type\": \"DELETE_ARTIFACT\",\n    \"occur_at\": 1656946862,\n    \"operator\": \"admin\",\n    \"event_data\": {\n      \"resources\": [\n        {\n          \"digest\": \"sha256:d3890814cc5a7cfc02403435281cdf51adfb6b67e223934d9d6137a4ad364286\",\n          \"tag\": \"1.21.6-debian-10-r117\",\n          \"resource_url\": \"harbor.jarvis.tanzu/veba-webhook/bitnami-nginx:1.21.6-debian-10-r117\"\n        }\n      ],\n      \"repository\": {\n        \"name\": \"bitnami-nginx\",\n        \"namespace\": \"veba-webhook\",\n        \"repo_full_name\": \"veba-webhook/bitnami-nginx\",\n        \"repo_type\": \"public\"\n      }\n    }\n  }\n"}

A beautified view is available in VEBA’s provided event viewer via https://<veba-fqdn>/events.

/img/posts/202207_harbor_webhhok_post/rguske-post-harbor-webhook-function-4.png
Figure IV: Harbor CloudEvent in Sockeye

Awesome! 🚀

🎥 kn-go-harbor-webhook function deployment 🎥

Deploy the kn-ps-harbor-slack Function

With the available CloudEvent payload, we can now configure and deploy other functions. As aforementioned (low hanging fruits), I wanted to get notified by actions happened related to my Harbor project (#ChatOps). The kn-ps-harbor-slack function will send a message to your Slack channel webhook.

There we go again… webhooks everywhere 😄

  1. Add your Slack channel webhook URL to the slack_secret.json file
  2. Create the Kubernetes secret
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# Create the harbor-slack-secret
$ kubectl -n vmware-functions create secret generic harbor-slack-secret --from-file=SLACK_SECRET=slack_secret.json

# Verify the creation of the secret
$ kubectl -n vmware-functions get secrets

NAME                    TYPE                                  DATA   AGE
harbor-slack-secret     Opaque                                1      1m
webhook-auth            kubernetes.io/basic-auth              2      9m
  1. Deploy the function.yaml

By default, the function deployment will filter on the com.vmware.harbor.push_artifact.v0 Harbor Event. If you wish to change this, update the type field within function.yaml to the desired event type. A list of supported notification events is available on the official Harbor documentation under Configure Webhook Notifications. As mentioned, use the VEBA event viewer endpoint (https://<veba-fqdn>/events) to display all incoming events.

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kubectl -n vmware-functions create -f - <<EOF
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: kn-ps-harbor-slack
  labels:
    app: veba-ui
spec:
  template:
    metadata:
      annotations:
        autoscaling.knative.dev/maxScale: "1"
        autoscaling.knative.dev/minScale: "1"
    spec:
      containers:
        - image: us.gcr.io/daisy-284300/veba/kn-ps-harbor-slack:1.0
          envFrom:
            - secretRef:
                name: harbor-slack-secret
          env:
            - name: FUNCTION_DEBUG
              value: "false"
---
apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: kn-ps-harbor-slack-trigger
  labels:
    app: veba-ui
spec:
  broker: default
  filter:
    attributes:
      type: com.vmware.harbor.push_artifact.v0
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: kn-ps-harbor-slack
EOF

When you are going to e.g. push or delete an artifact, a new message should show up in your Slack channel, like the provided example in Firgure V.

/img/posts/202207_harbor_webhhok_post/rguske-post-harbor-webhook-function-5.png
Figure V: Slack Notification delivered by kn-ps-harbor-slack Function

🎥 kn-ps-harbor-slack function deployment 🎥

As a side note: Harbor supports Slack as a configurable Notify Type OOB. But it sends the message in a raw JSON format. However, we also have a Microsoft Teams Function example available in PowerShell as well … 😉

Big THANKS to Michael for the great work on the kn-go-harbor-webhook function as well as for his review of this post.

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Updated on 2022-09-27  110e3f6
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