quickstarts/pub_sub/javascript/http

Dapr pub/sub

In this quickstart, you'll create a publisher microservice and a subscriber microservice to demonstrate how Dapr enables a publish-subcribe pattern. The publisher will generate messages of a specific topic, while subscribers will listen for messages of specific topics. See Why Pub-Sub to understand when this pattern might be a good choice for your software architecture.

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

Note: This example leverages HTTP requests only. If you are looking for the example using the Dapr Client SDK (recommended) click here.

This quickstart includes one publisher:

• Node client message generator checkout

And one subscriber:

• Node subscriber order-processor

Run all apps with multi-app run template file:

This section shows how to run both applications at once using multi-app run template files with dapr run -f .. This enables to you test the interactions between multiple applications.

1. Install dependencies:

cd ./order-processor
npm install
cd ..
cd ./checkout
npm install

2. Open a new terminal window and run the multi app run template:

dapr run -f .

The terminal console output should look similar to this:

== APP - checkout-sdk-http == Published data: {"orderId":1}
== APP - order-processor-http == Subscriber received: { orderId: 1 }
== APP - checkout-sdk-http == Published data: {"orderId":2}
== APP - order-processor-http == Subscriber received: { orderId: 2 }
== APP - checkout-sdk-http == Published data: {"orderId":3}
== APP - order-processor-http == Subscriber received: { orderId: 3 }
== APP - checkout-sdk-http == Published data: {"orderId":4}
== APP - order-processor-http == Subscriber received: { orderId: 4 }
== APP - checkout-sdk-http == Published data: {"orderId":5}
== APP - order-processor-http == Subscriber received: { orderId: 5 }
== APP - checkout-sdk-http == Published data: {"orderId":6}
== APP - order-processor-http == Subscriber received: { orderId: 6 }
== APP - checkout-sdk-http == Published data: {"orderId":7}
== APP - order-processor-http == Subscriber received: { orderId: 7 }
== APP - checkout-sdk-http == Published data: {"orderId":8}
== APP - order-processor-http == Subscriber received: { orderId: 8 }
== APP - checkout-sdk-http == Published data: {"orderId":9}
== APP - order-processor-http == Subscriber received: { orderId: 9 }
== APP - checkout-sdk-http == Published data: {"orderId":10}
== APP - order-processor-http == Subscriber received: { orderId: 10 }

3. Stop and clean up application processes

dapr stop -f .

Run a single app at a time with Dapr (Optional)

An alternative to running all or multiple applications at once is to run single apps one-at-a-time using multiple dapr run .. -- npm run start commands. This next section covers how to do this.

Run Node message subscriber with Dapr

1. Install dependencies:

cd ./order-processor
npm install

2. Run the Node publisher app with Dapr:

dapr run --app-port 5003 --app-id order-processing-http --app-protocol http --dapr-http-port 3501 --resources-path ../../../components -- npm run start

Run Node message publisher with Dapr

1. Install dependencies:

cd ./checkout
npm install

2. Run the Node publisher app with Dapr:

dapr run --app-id checkout-http --app-protocol http --dapr-http-port 3500 --resources-path ../../../components -- npm run start

Stop the apps and clean up

dapr stop --app-id checkout-http
dapr stop --app-id order-processor-http