OpenFaaS MinIO Notifications Webhook Function

MinIO is an open source object storage server with support for the S3 API. This means that you can run your very own S3 deployment from your homelab.

This repository creates and deploys an OpenFaaS Golang function that is used as a webhook by MinIO to receive notifications of events.

See the complete MinIO Bucket Notification Guide documentation for events and subscribing to them.

OpenFaas Slack Function

Whilst you can do anything you like with your OpenFaas function handler for these notification events, I have chosen to invoking another OpenFaaS function I have. This is the OpenFaaS Slack Function that you can locate in one of my other Github repositories. This is a simple function which takes a basic JSON payload and uses the slack-go library to send messages to a Slack channel.

Installing OpenFaaS

I'm not going to go into any great detail for installing and deploying OpenFaaS, I'll do that as a separate set of instructions later on. I essentially followed the directions from OpenFaas Deployment and used the awesome Arkade CLI installer for Kubernetes applications, plus some of the linked blog posts.

Private Docker Registry

When deploying functions from a private registry OpenFaaS needs the credentials to be able to authenticate to it when pulling images. See Use a private registry with Kubernetes for more information on this.

Run the below command to create the Docker registry credentials secret in the openfaas-fn namespace.

kubectl create secret docker-registry homelab-docker-registry \
  --docker-username=homelab-user \
  --docker-password=homelab-password \
  --docker-email=homelab@example.com \
  --docker-server=https://registry.mydomain.io \
  --namespace openfaas-fn

Add the below yaml to the default service account in the openfaas-fn namespace so that it has the credentials to authenticate with the registry when pulling images.

kubectl edit serviceaccount default -n openfaas-fn

imagePullSecrets:
  - name: homelab-docker-registry

Generating Go Type Definitions from JSON

The MinIO notification events are sent to the endpoint as a JSON payload. To be able to marshall the payloads into Go type definitions I have used the excellent online tool JSON-to-Go to generate these. By using example JSON payloads from MinIO you can easily generate the Go code.

Creating the Function

The below steps were followed to create a new function and handler.

Run the command below to pull the golang-http template that creates an HTTP request handler for Golang.

faas-cli template store pull golang-http

Run the command below to create the function definition files and empty function handler.

$ faas new --lang golang-http minio-notification-webhook
Folder: minio-notification-webhook created.
  ___                   _____           ____
 / _ \ _ __   ___ _ __ |  ___|_ _  __ _/ ___|
| | | | '_ \ / _ \ '_ \| |_ / _` |/ _` \___ \
| |_| | |_) |  __/ | | |  _| (_| | (_| |___) |
 \___/| .__/ \___|_| |_|_|  \__,_|\__,_|____/
      |_|


Function created in folder: minio-notification-webhook
Stack file written: minio-notification-webhook.yml

Golang Dependencies

This function uses additional Go libraries that need to be included as dependencies when building. See GO - Dependencies for options on including these dependencies. This repository uses Go Modules for managing dependencies.

The below commands were run to initialize the go.mod and go.sum files. These commands need to be run from within the slack directory containing the function handler.

$ cd minio-notification-webhook
$ export GO111MODULE=on

$ go mod init
go: creating new go.mod: module openfaas/openfaas-minio-notification-webhook/minio-notification-webhook

$ go get
go: finding module for package github.com/openfaas/templates-sdk/go-http
go: found github.com/openfaas/templates-sdk/go-http in github.com/openfaas/templates-sdk v0.0.0-20200723110415-a699ec277c12

$ go mod tidy

When adding new libraries within your handler source code you will need to update your Go dependencies.

cd minio-notification-webhook
go mod tidy

Building the Function

The OpenFaaS documentation and Simple Serverless with Golang Functions and Microservices provide instruction on how to develop and build OpenFaaS functions.

ARM64 Image Builds

This function is going to be deployed onto a Raspberry Pi using ARM64 so the build and deploy process is slightly different than a basic faas-cli up command. The below command will create a new directory containing the Dockerfile and artifacts that will be used to build the container image.

faas-cli build --shrinkwrap -f minio-notification-webhook.yml

Docker Buildx for multiple platforms

The below commands should only need to be run once but will create a new Docker build context for using with Docker Buildx to create images for multiple platforms.

export DOCKER_CLI_EXPERIMENTAL=enabled
docker buildx create --use --name=multiarch
docker buildx inspect --bootstrap

Run the below command to use Buildx to create an image that supports both amd64 and arm64 architectures, and push it to the registry. This sets the GO111MODULE build arg to on so that the Go dependencies are retrieved during the build process. Whilst the GO111MODULE entry can be added to the slack.yml file as per the OpenFaaS documentation this does not appear to be used when performing shrinkwrap builds, the argument must still be provided when running docker buildx build.

$ docker buildx build \
 --build-arg GO111MODULE=on \
 --push \
 --tag registry.mydomain.io/openfaas/minio-notification-webhook:latest \
 --platform=linux/amd64,linux/arm64 \
 build/minio-notification-webhook/

Deploying the Function

Run the below commands to point to the OpenFaaS gateway and authenticate.

$ export OPENFAAS_URL=https://gateway.mydomain.io
$ export PASSWORD=$(kubectl get secret -n openfaas basic-auth -o jsonpath="{.data.basic-auth-password}" | base64 --decode; echo)

$ echo -n $PASSWORD | faas-cli login --username admin --password-stdin
Calling the OpenFaaS server to validate the credentials...
credentials saved for admin https://gateway.mydomain.io

$ faas-cli deploy \
  --image registry.mydomain.io/openfaas/minio-notification-webhook:latest \
  --name minio-notification-webhook \
  --env MINIO_DEBUG=true \
  --env MINIO_LOGLEVEL=debug \
  --env MINIO_SLACK_ENDPOINT=https://gateway.mydomain.io/function/slack

Deployed. 202 Accepted.
URL: https://gateway.mydomain.io/function/minio-notification-webhook

Run the below command to remove the function.

faas-cli remove minio-notification-webhook

Subscribing to MinIO S3 Notifications

Start MinIO with the below environment variables to enable a notification webhook. The _SLACK suffix can be named anything but is used to uniquely identify the configuration for this notifier. This needs to match the arn for the webhook as well, i.e. arn:minio:sqs::SLACK:webhook

Name	Value
MINIO_NOTIFY_WEBHOOK_ENABLE_SLACK	on
MINIO_NOTIFY_WEBHOOK_ENDPOINT_SLACK	https://gateway.mydomain.io/function/minio-notification-webhook
MINIO_NOTIFY_WEBHOOK_QUEUE_LIMIT	10

Run the below commands to subscribe to events so that MinIO will send notification events for objects uploaded, modified, retrieved and deleted in the projects S3 bucket.

$ mc event add myminio/projects arn:minio:sqs::SLACK:webhook --event put
$ mc event add myminio/projects arn:minio:sqs::SLACK:webhook --event delete
$ mc event add myminio/projects arn:minio:sqs::SLACK:webhook --event get

$ mc event list myminio/projects
arn:minio:sqs::SLACK:webhook   s3:ObjectCreated:*   Filter:
arn:minio:sqs::SLACK:webhook   s3:ObjectRemoved:*   Filter:
arn:minio:sqs::SLACK:webhook   s3:ObjectAccessed:*   Filter:

Example json payload for upload of object to S3 bucket.

{
  "EventName": "s3:ObjectCreated:Put",
  "Key": "projects/grafana-monitoring-dashboard.json",
  "Records": [
    {
      "eventVersion": "2.0",
      "eventSource": "minio:s3",
      "awsRegion": "",
      "eventTime": "2021-03-11T07:47:11.994Z",
      "eventName": "s3:ObjectCreated:Put",
      "userIdentity": { "principalId": "XXXXXXXXXX" },
      "requestParameters": {
        "accessKey": "XXXXXXXXXXX",
        "region": "",
        "sourceIPAddress": "10.42.0.156"
      },
      "responseElements": {
        "x-amz-request-id": "166B3A2756316F44",
        "x-minio-deployment-id": "cf5765d8-f665-4689-a019-7481c31c367c",
        "x-minio-origin-endpoint": "http://10.42.0.184:9000"
      },
      "s3": {
        "s3SchemaVersion": "1.0",
        "configurationId": "Config",
        "bucket": {
          "name": "projects",
          "ownerIdentity": { "principalId": "XXXXXXXXXX" },
          "arn": "arn:aws:s3:::projects"
        },
        "object": {
          "key": "grafana-monitoring-dashboard.json",
          "size": 35305,
          "eTag": "c9103045dfdda632353ddc99dab4a674",
          "contentType": "application/json",
          "userMetadata": { "content-type": "application/json" },
          "sequencer": "166B3A2757D47132"
        }
      },
      "source": {
        "host": "10.42.0.156",
        "port": "",
        "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.72 Safari/537.36"
      }
    }
  ]
}

Example json payload for an object deleted from an S3 bucket.

{
  "EventName": "s3:ObjectRemoved:Delete",
  "Key": "projects/grafana-monitoring-dashboard.json",
  "Records": [
    {
      "eventVersion": "2.0",
      "eventSource": "minio:s3",
      "awsRegion": "",
      "eventTime": "2021-03-11T07:48:28.303Z",
      "eventName": "s3:ObjectRemoved:Delete",
      "userIdentity": { "principalId": "XXXXXXXXX" },
      "requestParameters": {
        "accessKey": "XXXXXXXXXXX",
        "region": "",
        "sourceIPAddress": "10.42.0.156"
      },
      "responseElements": {
        "x-amz-request-id": "",
        "x-minio-deployment-id": "cf5765d8-f665-4689-a019-7481c31c367c",
        "x-minio-origin-endpoint": "http://10.42.0.184:9000"
      },
      "s3": {
        "s3SchemaVersion": "1.0",
        "configurationId": "Config",
        "bucket": {
          "name": "projects",
          "ownerIdentity": { "principalId": "XXXXXXXXXXX" },
          "arn": "arn:aws:s3:::projects"
        },
        "object": {
          "key": "grafana-monitoring-dashboard.json",
          "sequencer": "166B3A391C3CFD09"
        }
      },
      "source": {
        "host": "10.42.0.156",
        "port": "",
        "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.72 Safari/537.36"
      }
    }
  ]
}

Credits

Credits to Matt Holt for the json-to-go online tool for making my life easy to generate Go type definitions from JSON.

License