mirror of https://github.com/dapr/quickstarts.git
129 lines
4.2 KiB
Markdown
129 lines
4.2 KiB
Markdown
# Dapr pub/sub
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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](#why-pub-sub) to understand when this pattern might be a good choice for your software architecture.
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Visit [this](https://docs.dapr.io/developing-applications/building-blocks/pubsub/) link for more information about Dapr and Pub-Sub.
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> **Note:** This example leverages HTTP `requests` only. If you are looking for the example using the Dapr Client SDK (recommended) [click here](../sdk/).
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This quickstart includes one publisher:
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- Node client message generator `checkout`
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And one subscriber:
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- Node subscriber `order-processor`
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## Run all apps with multi-app run template file:
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This section shows how to run both applications at once using [multi-app run template files](https://docs.dapr.io/developing-applications/local-development/multi-app-dapr-run/multi-app-overview/) with `dapr run -f .`. This enables to you test the interactions between multiple applications.
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1. Install dependencies:
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<!-- STEP
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name: Install Node dependencies
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-->
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```bash
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cd ./order-processor
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npm install
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cd ..
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cd ./checkout
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npm install
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```
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<!-- END_STEP -->
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2. Open a new terminal window and run the multi app run template:
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<!-- STEP
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name: Run multi app run template
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expected_stdout_lines:
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- 'Started Dapr with app id "order-processor-http"'
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- 'Started Dapr with app id "checkout-http"'
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- '== APP - checkout-http == Published data: {"orderId":10}'
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- '== APP - order-processor-http == Subscriber received: { orderId: 10 }'
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expected_stderr_lines:
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output_match_mode: substring
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match_order: none
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background: true
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sleep: 15
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timeout_seconds: 30
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-->
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```bash
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dapr run -f .
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```
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The terminal console output should look similar to this:
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```text
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== APP - checkout-sdk-http == Published data: {"orderId":1}
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== APP - order-processor-http == Subscriber received: { orderId: 1 }
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== APP - checkout-sdk-http == Published data: {"orderId":2}
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== APP - order-processor-http == Subscriber received: { orderId: 2 }
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== APP - checkout-sdk-http == Published data: {"orderId":3}
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== APP - order-processor-http == Subscriber received: { orderId: 3 }
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== APP - checkout-sdk-http == Published data: {"orderId":4}
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== APP - order-processor-http == Subscriber received: { orderId: 4 }
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== APP - checkout-sdk-http == Published data: {"orderId":5}
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== APP - order-processor-http == Subscriber received: { orderId: 5 }
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== APP - checkout-sdk-http == Published data: {"orderId":6}
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== APP - order-processor-http == Subscriber received: { orderId: 6 }
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== APP - checkout-sdk-http == Published data: {"orderId":7}
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== APP - order-processor-http == Subscriber received: { orderId: 7 }
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== APP - checkout-sdk-http == Published data: {"orderId":8}
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== APP - order-processor-http == Subscriber received: { orderId: 8 }
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== APP - checkout-sdk-http == Published data: {"orderId":9}
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== APP - order-processor-http == Subscriber received: { orderId: 9 }
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== APP - checkout-sdk-http == Published data: {"orderId":10}
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== APP - order-processor-http == Subscriber received: { orderId: 10 }
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```
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3. Stop and clean up application processes
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```bash
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dapr stop -f .
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```
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<!-- END_STEP -->
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## Run a single app at a time with Dapr (Optional)
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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.
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### Run Node message subscriber with Dapr
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1. Install dependencies:
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```bash
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cd ./order-processor
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npm install
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```
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2. Run the Node publisher app with Dapr:
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```bash
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dapr run --app-port 5003 --app-id order-processing-http --app-protocol http --dapr-http-port 3501 --resources-path ../../../components -- npm run start
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```
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### Run Node message publisher with Dapr
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1. Install dependencies:
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```bash
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cd ./checkout
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npm install
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```
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2. Run the Node publisher app with Dapr:
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```bash
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dapr run --app-id checkout-http --app-protocol http --dapr-http-port 3500 --resources-path ../../../components -- npm run start
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```
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### Stop the apps and clean up
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```bash
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dapr stop --app-id checkout-http
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dapr stop --app-id order-processor-http
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```
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