Python using RabbitMQ

This app provides a minimal example of a chat app, sending messages to all clients that are currently connected.

It consists of a simple static webpage with minimal scripts to send messages through the application server to a connected RabbitMQ cluster. Due to the exchange type "fanout", all messages will be relayed to all connected clients.

Note this is a minimal example which does not consider persistence, reconnection / error handling, cleaning up etc.

Why using RabbitMQ?

The application server accepts the websocket connections, and would generally be able to exchange messages between them. However, typically multiple application server instances exist, and usually not all clients are connected to the same instance. The RabbitMQ cluster takes care of exchanging the messages between those.

Running the example

Platform preparation

The platform admin needs to activate RabbitMQ and Harbor in the Platform Apps.

Building the app

The app does not include a .Dockerfile, but an image can be created using Buildpacks.

1. In the app platform, select Build, then Create Build.
2. Provide an image name, e.g. rmq-example-app.
3. Select as Mode Buildpacks.
4. Set the Repo URL to https://github.com/linode/apl-examples.git.
5. Set the path to rabbitmq-python-example.
6. Confirm with Submit.
7. Copy out the image repository for creating the workload in the following step.

Creating the workloads

Creating the RabbitMQ cluster

1. Go to Workloads, then Create Workload.
2. Select RabbitMQ-Cluster.
3. Set a name, e.g. example.
4. Click Submit.

Creating the application server deployment

1. Go to Workloads, then Create Workload.
2. Select K8s-Deployment.
3. Set a name, e.g. rmq-example-app.
4. In the chart values, update the image and env section. Adjust image.repository with the value from the build. Also, update the name references in the secretKeyRef entries. The format of the secret name is <name>-rabbitmq-cluster-default-user, where <name> is to be replaced with the cluster name you chose above. It should look like this:

image:
  repository: <your-image-repo>
  pullPolicy: IfNotPresent
  tag: latest
env:
  - name: NOTIFIER_RABBITMQ_HOST
    valueFrom:
      secretKeyRef:
        name: example-rabbitmq-cluster-default-user
        key: host
  - name: NOTIFIER_RABBITMQ_USER
    valueFrom:
      secretKeyRef:
        name: example-rabbitmq-cluster-default-user
        key: username
  - name: NOTIFIER_RABBITMQ_PASSWORD
    valueFrom:
      secretKeyRef:
        name: example-rabbitmq-cluster-default-user
        key: password

Create a networking policy

1. Go to Network Policies, select Create Netpol.
2. Provide any name for the policy, e.g. rabbitmq-example.
3. Rule type is ingress. Set the selector name otomi.io/app and value example-rabbitmq-cluster, where applicable replacing example with the name you chose for the RabbitMQ instance.
4. Set mode to AllowOnly.
5. Set the namespace to team-<team-name>, according to the team deploying the application, e.g. team-demo.
6. Optionally limit the in-cluster exposure to the app, i.e. set the selector label name to otomi.io/app and the selector label value to the name of your app workload, e.g. rmq-example-app.

Exposing the service

1. As soon as the workload is deployed, go to Services and Create Service.
2. Select the name of your workload from the list, e.g. rmq-example-app.
3. Under Exposure, select External
4. Confirm with Submit.

As soon as the service is configured, the app should be available using the link URL in the application platform console.