mirror of https://github.com/dapr/quickstarts.git
138 lines
5.8 KiB
Markdown
138 lines
5.8 KiB
Markdown
# Dapr pub/sub
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In this quickstart, there is a publisher microservice `checkout` and a subscriber microservice `order-processor` to demonstrate how Dapr enables a publish-subscribe pattern. `checkout` generates messages and publishes to a specific orders topic, and `order-processor` subscribers listen for messages of topic orders.
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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 the Dapr client SDK. If you are looking for the example using only HTTP [click here](../http).
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This quickstart includes one publisher:
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- Java client message generator `checkout`
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And one subscriber:
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- Java subscriber `order-processor`
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## Pre-requisites
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* [Dapr and Dapr Cli](https://docs.dapr.io/getting-started/install-dapr-cli/).
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* Java JDK 17 (or greater):
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* [Microsoft JDK 17](https://learn.microsoft.com/en-us/java/openjdk/download#openjdk-17)
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* [Oracle JDK 17](https://www.oracle.com/java/technologies/downloads/?er=221886#java17)
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* [OpenJDK 17](https://jdk.java.net/17/)
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* [Apache Maven](https://maven.apache.org/install.html) version 3.x.
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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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mvn clean install
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cd ..
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cd ./checkout
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mvn clean install
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cd ..
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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-sdk"'
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- 'Started Dapr with app id "checkout-sdk"'
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- 'Published data: 2'
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- 'Subscriber received: 2'
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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 == 563 [main] INFO com.service.CheckoutServiceApplication - Published data: 1
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== APP - order-processor-sdk == 2023-09-04 13:57:18.434 INFO 82828 --- [nio-8080-exec-3] c.s.c.OrderProcessingServiceController : Subscriber received: 1
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== APP - checkout-sdk == 1576 [main] INFO com.service.CheckoutServiceApplication - Published data: 2
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== APP - order-processor-sdk == 2023-09-04 13:57:19.419 INFO 82828 --- [nio-8080-exec-4] c.s.c.OrderProcessingServiceController : Subscriber received: 2
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== APP - checkout-sdk == 2587 [main] INFO com.service.CheckoutServiceApplication - Published data: 3
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== APP - order-processor-sdk == 2023-09-04 13:57:20.431 INFO 82828 --- [nio-8080-exec-5] c.s.c.OrderProcessingServiceController : Subscriber received: 3
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== APP - checkout-sdk == 3602 [main] INFO com.service.CheckoutServiceApplication - Published data: 4
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== APP - order-processor-sdk == 2023-09-04 13:57:21.447 INFO 82828 --- [nio-8080-exec-6] c.s.c.OrderProcessingServiceController : Subscriber received: 4
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== APP - checkout-sdk == 4612 [main] INFO com.service.CheckoutServiceApplication - Published data: 5
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== APP - order-processor-sdk == 2023-09-04 13:57:22.455 INFO 82828 --- [nio-8080-exec-7] c.s.c.OrderProcessingServiceController : Subscriber received: 5
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== APP - checkout-sdk == 5624 [main] INFO com.service.CheckoutServiceApplication - Published data: 6
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== APP - order-processor-sdk == 2023-09-04 13:57:23.468 INFO 82828 --- [nio-8080-exec-8] c.s.c.OrderProcessingServiceController : Subscriber received: 6
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== APP - checkout-sdk == 6631 [main] INFO com.service.CheckoutServiceApplication - Published data: 7
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== APP - order-processor-sdk == 2023-09-04 13:57:24.474 INFO 82828 --- [nio-8080-exec-9] c.s.c.OrderProcessingServiceController : Subscriber received: 7
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== APP - checkout-sdk == 7643 [main] INFO com.service.CheckoutServiceApplication - Published data: 8
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== APP - order-processor-sdk == 2023-09-04 13:57:25.487 INFO 82828 --- [io-8080-exec-10] c.s.c.OrderProcessingServiceController : Subscriber received: 8
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== APP - checkout-sdk == 8649 [main] INFO com.service.CheckoutServiceApplication - Published data: 9
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== APP - order-processor-sdk == 2023-09-04 13:57:26.492 INFO 82828 --- [nio-8080-exec-2] c.s.c.OrderProcessingServiceController : Subscriber received: 9
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== APP - checkout-sdk == 9662 [main] INFO com.service.CheckoutServiceApplication - Published data: 10
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== APP - order-processor-sdk == 2023-09-04 13:57:27.504 INFO 82828 --- [nio-8080-exec-1] c.s.c.OrderProcessingServiceController : Subscriber received: 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 .. -- dotnet run` commands. This next section covers how to do this.
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### Run Java message subscriber app with Dapr
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1. Navigate to directory and install dependencies:
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```bash
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cd ./order-processor
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mvn clean install
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```
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2. Run the Java subscriber app with Dapr:
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```bash
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cd ./order-processor
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dapr run --app-port 8080 --app-id order-processor-sdk --resources-path ../../../components -- java -jar target/OrderProcessingService-0.0.1-SNAPSHOT.jar
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```
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### Run Java message publisher app with Dapr
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1. Navigate to the directory and install dependencies:
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```bash
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cd ./checkout
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mvn clean install
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```
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2. Run the Java publisher app with Dapr:
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```bash
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cd ./checkout
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dapr run --app-id checkout-sdk --resources-path ../../../components -- java -jar target/CheckoutService-0.0.1-SNAPSHOT.jar
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```
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```bash
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dapr stop --app-id checkout-sdk
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dapr stop --app-id order-processor-sdk
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```
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