Dapr pub/sub

Background

This repo uses python flask based REST-API microservices, redis and dapr runtime to enable publish-subscribe pattern. I have included docker-compose in it to run it as full fledged app in the system including all components.

For more details about this quickstart example please see the Pub-Sub Quickstart documentation.

Visit this link for more information about Dapr and Pub-Sub.

This quickstart includes one publisher:

• Python client message generator checkout

And one subscriber:

• Python subscriber order-processor

Pre-requisites

• Dapr CLI
• Docker Desktop

Running using docker-compose

• A docker compose file is created to dockerize the checkout and order processing.
  Use below commands to run :-

  • docker-compose build
  • docker-compose up

  Redis is used as message-broker, docker-compose will create all the containers including microservices and redis container.

• Send event using postman or by using python script.

  • Using Postman.
    Send below json in body of the message.

    {
      "orderId": "anyorderid"
    } 

  • Using curl

    curl --location 'http://localhost:3000/publish' \
      --header 'Content-Type: application/json' \
      --data '{
          "orderId": "testorder12345"
      }'
    

• Sample output

Running using Kubernetes

• Tested with Docker-Desktop's inbuilt kubernetes offering. Enable Kubernetes in the settings of Docker desktop.

  • Create a namespace in kubernetes cluster using
    kubectl create namespace test

  • Set the namespace as default using
    kubectl config set-context --current --namespace=test

  • Install Dapr to kubernetes namespace (requires Dapr CLI to be installed in system)
    dapr init -k -n test
    Above will install all the dependencies of dapr

  • Change to directory dapr_python_redis\dapr\kubernetes and then run below command
    kubectl apply -f pubsub.yaml -n test
    Above command will add the pubsub binding we use for communicating with redis

  • Change back to root directory of the repo and run below commands -

    kubectl apply -f kubedeploy.yml -n test

  • Check if all services and pods are up using Lens or with cli using below commands

    kubectl get pods -n test
    kubectl get service -n test
    

  • Send event from postman or using curl using same approach as in docker-compose.

• Sample output

Reference links

https://docs.dapr.io/getting-started/
https://docs.dapr.io/getting-started/quickstarts/pubsub-quickstart/
https://docs.dapr.io/developing-applications/building-blocks/bindings/howto-triggers/