mirror of https://github.com/dapr/quickstarts.git
145 lines
5.1 KiB
Markdown
145 lines
5.1 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 the Dapr client SDK. If you are looking for the example using only HTTP `requests` [click here](../http).
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This quickstart includes one publisher:
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- Python client message generator `checkout`
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And one subscriber:
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- Python 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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1. Run the Python subscriber app (flask version) with Dapr:
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<!-- STEP
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name: Install Python dependencies
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-->
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```bash
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cd ./checkout
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pip3 install -r requirements.txt
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cd ..
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cd ./order-processor
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pip3 install -r requirements.txt
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cd ..
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cd ./order-processor-fastapi
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pip3 install -r requirements.txt
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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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- '== APP - checkout-sdk == INFO:root:Published data: {"orderId": 1}'
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- '== APP - order-processor-sdk == Subscriber received : 1'
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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 == INFO:root:Published data: {"orderId": 1}
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== APP - order-processor-sdk == Subscriber received : 1
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:19] "POST /orders HTTP/1.1" 200 -
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== APP - checkout-sdk == INFO:root:Published data: {"orderId": 2}
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:20] "POST /orders HTTP/1.1" 200 -
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== APP - order-processor-sdk == Subscriber received : 2
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== APP - checkout-sdk == INFO:root:Published data: {"orderId": 3}
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== APP - order-processor-sdk == Subscriber received : 3
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:21] "POST /orders HTTP/1.1" 200 -
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== APP - checkout-sdk == INFO:root:Published data: {"orderId": 4}
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== APP - order-processor-sdk == Subscriber received : 4
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:22] "POST /orders HTTP/1.1" 200 -
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== APP - checkout-sdk == INFO:root:Published data: {"orderId": 5}
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== APP - order-processor-sdk == Subscriber received : 5
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:23] "POST /orders HTTP/1.1" 200 -
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== APP - checkout-sdk == INFO:root:Published data: {"orderId": 6}
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== APP - order-processor-sdk == Subscriber received : 6
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:24] "POST /orders HTTP/1.1" 200 -
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== APP - checkout-sdk == INFO:root:Published data: {"orderId": 7}
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:25] "POST /orders HTTP/1.1" 200 -
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== APP - order-processor-sdk == Subscriber received : 7
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== APP - checkout-sdk == INFO:root:Published data: {"orderId": 8}
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:26] "POST /orders HTTP/1.1" 200 -
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== APP - order-processor-sdk == Subscriber received : 8
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== APP - checkout-sdk == INFO:root:Published data: {"orderId": 9}
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== APP - order-processor-sdk == 127.0.0.1 - - [04/Sep/2023 11:15:27] "POST /orders HTTP/1.1" 200 -
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== APP - order-processor-sdk == Subscriber received : 9
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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 .. -- python3 app.py` commands. This next section covers how to do this.
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### Run Python 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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pip3 install -r requirements.txt
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```
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2. Run the Python subscriber app with Dapr:
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```bash
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dapr run --app-id order-processor-sdk --resources-path ../../../components/ --app-port 6001 -- uvicorn app:app --port 6002
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```
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### Run Python 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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pip3 install -r requirements.txt
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```
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2. Run the Python publisher app with Dapr:
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```bash
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dapr run --app-id checkout-sdk --resources-path ../../../components/ -- python3 app.py
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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-sdk
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dapr stop --app-id order-processor-sdk
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dapr stop --app-id order-processor-sdk-fastapi
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```
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