quickstarts/service_invocation/python/http/README.md

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# Service Invocation
In this quickstart, you'll create a checkout service and an order processor service to demonstrate how to use the service invocation API. The checkout service uses Dapr's http proxying capability to invoke a method on the order processing service.
Visit [this](https://docs.dapr.io/developing-applications/building-blocks/service-invocation/) link for more information about Dapr and service invocation.
This quickstart includes one checkout service:
- Python client service `checkout`
And one order processor service:
- Python order-processor service `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](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.
1. Open a new terminal window and install dependencies for `order-processor` and `checkout` apps:
<!-- STEP
name: Install Node dependencies for order-processor and checkout
-->
```bash
cd ./order-processor
pip3 install -r requirements.txt
cd ../checkout
pip3 install -r requirements.txt
cd ..
```
<!-- END_STEP -->
2. Run the multi app run template:
<!-- STEP
name: Run multi app run template
expected_stdout_lines:
- 'Validating config and starting app "order-processor"'
- 'Started Dapr with app id "order-processor"'
- 'Writing log files to directory'
- 'Validating config and starting app "checkout"'
- 'Started Dapr with app id "checkout"'
- 'Writing log files to directory'
expected_stderr_lines:
output_match_mode: substring
match_order: none
background: true
sleep: 15
timeout_seconds: 30
-->
```bash
dapr run -f .
```
The terminal console output should look similar to this:
```text
== APP - order-processor == Order received : {"orderId": 1}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 1}
== APP - order-processor == Order received : {"orderId": 2}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 2}
== APP - order-processor == Order received : {"orderId": 3}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 3}
== APP - order-processor == Order received : {"orderId": 4}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 4}
== APP - order-processor == Order received : {"orderId": 5}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 5}
== APP - order-processor == Order received : {"orderId": 6}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 6}
== APP - order-processor == Order received : {"orderId": 7}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 7}
== APP - order-processor == Order received : {"orderId": 8}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 8}
== APP - order-processor == Order received : {"orderId": 9}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 9}
== APP - order-processor == Order received : {"orderId": 10}
== APP - order-processor == 127.0.0.1 - - [DATE] "POST /orders HTTP/1.1" 200 -
== APP - checkout == Order passed: {"orderId": 10}
```
3. Stop and clean up application processes
```bash
dapr stop -f .
```
<!-- END_STEP -->
## 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 .. -- python3 app.py` commands. This next section covers how to do this.
### Run Python order-processor with Dapr
1. Install dependencies for `order-processor` app:
```bash
cd ./order-processor
pip3 install -r requirements.txt
```
2. Run the Python order-processor app with Dapr:
```bash
dapr run --app-port 8001 --app-id order-processor --app-protocol http --dapr-http-port 3501 -- python3 app.py
```
### Run Python checkout with Dapr
1. Open a new terminal window and install dependencies for `checkout` app:
```bash
cd ./checkout
pip3 install -r requirements.txt
```
2. Run the Python checkout app with Dapr:
```bash
dapr run --app-id checkout --app-protocol http --dapr-http-port 3500 -- python3 app.py
```
### Stop and clean up application processes
```bash
dapr stop --app-id checkout
dapr stop --app-id order-processor
```