Quickstart: Service Invocation

Get started with Dapr’s Service Invocation building block

With Dapr’s Service Invocation building block, your application can communicate reliably and securely with other applications.

Dapr offers several methods for service invocation, which you can choose depending on your scenario. For this Quickstart, you’ll enable the checkout service to invoke a method using HTTP proxy in the order-processor service.

Learn more about Dapr’s methods for service invocation in the overview article.

Select your preferred language before proceeding with the Quickstart.

Python
JavaScript
.NET
Java
Go

Step 1: Pre-requisites

For this example, you will need:

Step 2: Set up the environment

Clone the sample provided in the Quickstarts repo.

git clone https://github.com/dapr/quickstarts.git

Step 3: Run `order-processor` service

In a terminal window, from the root of the Quickstart clone directory navigate to order-processor directory.

cd service_invocation/python/http/order-processor

Install the dependencies and build the application:

pip3 install -r requirements.txt

Run the order-processor service alongside a Dapr sidecar.

dapr run --app-port 8001 --app-id order-processor --app-protocol http --dapr-http-port 3501 -- python3 app.py

Note: Since Python3.exe is not defined in Windows, you may need to use python app.py instead of python3 app.py.

@app.route('/orders', methods=['POST'])
def getOrder():
    data = request.json
    print('Order received : ' + json.dumps(data), flush=True)
    return json.dumps({'success': True}), 200, {
        'ContentType': 'application/json'}
app.run(port=8001)

Step 4: Run `checkout` service

In a new terminal window, from the root of the Quickstart clone directory navigate to the checkout directory.

cd service_invocation/python/http/checkout

Install the dependencies and build the application:

pip3 install -r requirements.txt

Run the checkout service alongside a Dapr sidecar.

dapr run --app-id checkout --app-protocol http --dapr-http-port 3500 -- python3 app.py

Note: Since Python3.exe is not defined in Windows, you may need to use python app.py instead of python3 app.py.

In the checkout service, you’ll notice there’s no need to rewrite your app code to use Dapr’s service invocation. You can enable service invocation by simply adding the dapr-app-id header, which specifies the ID of the target service.

headers = {'dapr-app-id': 'order-processor'}
result = requests.post(
    url='%s/orders' % (base_url),
    data=json.dumps(order),
    headers=headers
)

Step 5: Use with Multi-App Run

You can run the Dapr applications in this quickstart with the Multi-App Run template. Instead of running two separate dapr run commands for the order-processor and checkout applications, run the following command:

dapr run -f .

To stop all applications, run:

dapr stop -f .

Step 6: View the Service Invocation outputs

Dapr invokes an application on any Dapr instance. In the code, the sidecar programming model encourages each application to talk to its own instance of Dapr. The Dapr instances then discover and communicate with one another.

checkout service output:

== APP == Order passed: {"orderId": 1}
== APP == Order passed: {"orderId": 2}
== APP == Order passed: {"orderId": 3}
== APP == Order passed: {"orderId": 4}
== APP == Order passed: {"orderId": 5}
== APP == Order passed: {"orderId": 6}
== APP == Order passed: {"orderId": 7}
== APP == Order passed: {"orderId": 8}
== APP == Order passed: {"orderId": 9}
== APP == Order passed: {"orderId": 10}

order-processor service output:

== APP == Order received: {"orderId": 1}
== APP == Order received: {"orderId": 2}
== APP == Order received: {"orderId": 3}
== APP == Order received: {"orderId": 4}
== APP == Order received: {"orderId": 5}
== APP == Order received: {"orderId": 6}
== APP == Order received: {"orderId": 7}
== APP == Order received: {"orderId": 8}
== APP == Order received: {"orderId": 9}
== APP == Order received: {"orderId": 10}

Step 1: Pre-requisites

For this example, you will need:

Step 2: Set up the environment

Clone the sample provided in the Quickstarts repo.

git clone https://github.com/dapr/quickstarts.git

Step 3: Run `order-processor` service

In a terminal window, from the root of the Quickstart clone directory navigate to order-processor directory.

cd service_invocation/javascript/http/order-processor

Install the dependencies:

npm install

Run the order-processor service alongside a Dapr sidecar.

dapr run --app-port 5001 --app-id order-processor --app-protocol http --dapr-http-port 3501 -- npm start

app.post('/orders', (req, res) => {
    console.log("Order received:", req.body);
    res.sendStatus(200);
});

Step 4: Run `checkout` service

In a new terminal window, from the root of the Quickstart clone directory navigate to the checkout directory.

cd service_invocation/javascript/http/checkout

Install the dependencies:

npm install

Run the checkout service alongside a Dapr sidecar.

dapr run --app-id checkout --app-protocol http --dapr-http-port 3500 -- npm start

let axiosConfig = {
  headers: {
      "dapr-app-id": "order-processor"
  }
};
const res = await axios.post(`${DAPR_HOST}:${DAPR_HTTP_PORT}/orders`, order , axiosConfig);
console.log("Order passed: " + res.config.data);

Step 5: Use with Multi-App Run

dapr run -f .

To stop all applications, run:

dapr stop -f .

Step 6: View the Service Invocation outputs

checkout service output:

== APP == Order passed: {"orderId": 1}
== APP == Order passed: {"orderId": 2}
== APP == Order passed: {"orderId": 3}
== APP == Order passed: {"orderId": 4}
== APP == Order passed: {"orderId": 5}
== APP == Order passed: {"orderId": 6}
== APP == Order passed: {"orderId": 7}
== APP == Order passed: {"orderId": 8}
== APP == Order passed: {"orderId": 9}
== APP == Order passed: {"orderId": 10}

order-processor service output:

== APP == Order received: {"orderId": 1}
== APP == Order received: {"orderId": 2}
== APP == Order received: {"orderId": 3}
== APP == Order received: {"orderId": 4}
== APP == Order received: {"orderId": 5}
== APP == Order received: {"orderId": 6}
== APP == Order received: {"orderId": 7}
== APP == Order received: {"orderId": 8}
== APP == Order received: {"orderId": 9}
== APP == Order received: {"orderId": 10}

Step 1: Pre-requisites

For this example, you will need:

Step 2: Set up the environment

Clone the sample provided in the Quickstarts repo.

git clone https://github.com/dapr/quickstarts.git

Step 3: Run `order-processor` service

In a terminal window, from the root of the Quickstart clone directory navigate to order-processor directory.

cd service_invocation/csharp/http/order-processor

Install the dependencies:

dotnet restore
dotnet build

Run the order-processor service alongside a Dapr sidecar.

dapr run --app-port 7001 --app-id order-processor --app-protocol http --dapr-http-port 3501 -- dotnet run

Below is the working code block from the order processor’s Program.cs file.

app.MapPost("/orders", (Order order) =>
{
    Console.WriteLine("Order received : " + order);
    return order.ToString();
});

Step 4: Run `checkout` service

In a new terminal window, from the root of the Quickstart clone directory navigate to the checkout directory.

cd service_invocation/csharp/http/checkout

Install the dependencies:

dotnet restore
dotnet build

Run the checkout service alongside a Dapr sidecar.

dapr run --app-id checkout --app-protocol http --dapr-http-port 3500 -- dotnet run

In the Program.cs file for the checkout service, you’ll notice there’s no need to rewrite your app code to use Dapr’s service invocation. You can enable service invocation by simply adding the dapr-app-id header, which specifies the ID of the target service.

var client = new HttpClient();
client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.Add("dapr-app-id", "order-processor");
var response = await client.PostAsync($"{baseURL}/orders", content);
    Console.WriteLine("Order passed: " + order);

Step 5: Use with Multi-App Run

dapr run -f .

To stop all applications, run:

dapr stop -f .

Step 6: View the Service Invocation outputs

checkout service output:

== APP == Order passed: Order { OrderId: 1 }
== APP == Order passed: Order { OrderId: 2 }
== APP == Order passed: Order { OrderId: 3 }
== APP == Order passed: Order { OrderId: 4 }
== APP == Order passed: Order { OrderId: 5 }
== APP == Order passed: Order { OrderId: 6 }
== APP == Order passed: Order { OrderId: 7 }
== APP == Order passed: Order { OrderId: 8 }
== APP == Order passed: Order { OrderId: 9 }
== APP == Order passed: Order { OrderId: 10 }

order-processor service output:

== APP == Order received: Order { OrderId: 1 }
== APP == Order received: Order { OrderId: 2 }
== APP == Order received: Order { OrderId: 3 }
== APP == Order received: Order { OrderId: 4 }
== APP == Order received: Order { OrderId: 5 }
== APP == Order received: Order { OrderId: 6 }
== APP == Order received: Order { OrderId: 7 }
== APP == Order received: Order { OrderId: 8 }
== APP == Order received: Order { OrderId: 9 }
== APP == Order received: Order { OrderId: 10 }

Step 1: Pre-requisites

For this example, you will need:

Dapr CLI and initialized environment.
Java JDK 11 (or greater):
- Oracle JDK, or
- OpenJDK
Apache Maven, version 3.x.
Docker Desktop

Step 2: Set up the environment

Clone the sample provided in the Quickstarts repo.

git clone https://github.com/dapr/quickstarts.git

Step 3: Run `order-processor` service

In a terminal window, from the root of the Quickstart clone directory navigate to order-processor directory.

cd service_invocation/java/http/order-processor

Install the dependencies:

mvn clean install

Run the order-processor service alongside a Dapr sidecar.

dapr run --app-id order-processor --app-port 9001 --app-protocol http --dapr-http-port 3501 -- java -jar target/OrderProcessingService-0.0.1-SNAPSHOT.jar

public String processOrders(@RequestBody Order body) {
        System.out.println("Order received: "+ body.getOrderId());
        return "CID" + body.getOrderId();
    }

Step 4: Run `checkout` service

In a new terminal window, from the root of the Quickstart clone directory navigate to the checkout directory.

cd service_invocation/java/http/checkout

Install the dependencies:

mvn clean install

Run the checkout service alongside a Dapr sidecar.

dapr run --app-id checkout --app-protocol http --dapr-http-port 3500 -- java -jar target/CheckoutService-0.0.1-SNAPSHOT.jar

.header("Content-Type", "application/json")
.header("dapr-app-id", "order-processor")
HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
System.out.println("Order passed: "+ orderId)

Step 5: Use with Multi-App Run

dapr run -f .

To stop all applications, run:

dapr stop -f .

Step 6: View the Service Invocation outputs

checkout service output:

== APP == Order passed: 1
== APP == Order passed: 2
== APP == Order passed: 3
== APP == Order passed: 4
== APP == Order passed: 5
== APP == Order passed: 6
== APP == Order passed: 7
== APP == Order passed: 8
== APP == Order passed: 9
== APP == Order passed: 10

order-processor service output:

== APP == Order received: 1
== APP == Order received: 2
== APP == Order received: 3
== APP == Order received: 4
== APP == Order received: 5
== APP == Order received: 6
== APP == Order received: 7
== APP == Order received: 8
== APP == Order received: 9
== APP == Order received: 10

Step 1: Pre-requisites

For this example, you will need:

Step 2: Set up the environment

Clone the sample provided in the Quickstarts repo.

git clone https://github.com/dapr/quickstarts.git

Step 3: Run `order-processor` service

In a terminal window, from the root of the Quickstart clone directory navigate to order-processor directory.

cd service_invocation/go/http/order-processor

Install the dependencies:

go build .

Run the order-processor service alongside a Dapr sidecar.

dapr run --app-port 6001 --app-id order-processor --app-protocol http --dapr-http-port 3501 -- go run .

Each order is received via an HTTP POST request and processed by the getOrder function.

func getOrder(w http.ResponseWriter, r *http.Request) {
    data, err := ioutil.ReadAll(r.Body)
    if err != nil {
        log.Fatal(err)
    }
    log.Printf("Order received : %s", string(data))
}

Step 4: Run `checkout` service

In a new terminal window, from the root of the Quickstart clone directory navigate to the checkout directory.

cd service_invocation/go/http/checkout

Install the dependencies:

go build .

Run the checkout service alongside a Dapr sidecar.

dapr run --app-id checkout --app-protocol http --dapr-http-port 3500 -- go run .

req.Header.Add("dapr-app-id", "order-processor")
response, err := client.Do(req)

Step 5: Use with Multi-App Run

dapr run -f .

To stop all applications, run:

dapr stop -f .

Step 6: View the Service Invocation outputs

checkout service output:

== APP == Order passed:  {"orderId":1}
== APP == Order passed:  {"orderId":2}
== APP == Order passed:  {"orderId":3}
== APP == Order passed:  {"orderId":4}
== APP == Order passed:  {"orderId":5}
== APP == Order passed:  {"orderId":6}
== APP == Order passed:  {"orderId":7}
== APP == Order passed:  {"orderId":8}
== APP == Order passed:  {"orderId":9}
== APP == Order passed:  {"orderId":10}

order-processor service output:

== APP == Order received :  {"orderId":1}
== APP == Order received :  {"orderId":2}
== APP == Order received :  {"orderId":3}
== APP == Order received :  {"orderId":4}
== APP == Order received :  {"orderId":5}
== APP == Order received :  {"orderId":6}
== APP == Order received :  {"orderId":7}
== APP == Order received :  {"orderId":8}
== APP == Order received :  {"orderId":9}
== APP == Order received :  {"orderId":10}

Tell us what you think!

We’re continuously working to improve our Quickstart examples and value your feedback. Did you find this Quickstart helpful? Do you have suggestions for improvement?

Join the discussion in our discord channel.

Next Steps

Learn more about Service Invocation as a Dapr building block
Learn more about how to invoke Dapr’s Service Invocation with:
- HTTP, or
- gRPC

Explore Dapr tutorials >>

Last modified February 14, 2023: update csharp code snippet (1e495c80)

Service Invocation

Quickstart: Service Invocation

Step 1: Pre-requisites

Step 2: Set up the environment

Step 3: Run order-processor service

Step 4: Run checkout service

Step 5: Use with Multi-App Run

Step 6: View the Service Invocation outputs

Step 1: Pre-requisites

Step 2: Set up the environment

Step 3: Run order-processor service

Step 4: Run checkout service

Step 5: Use with Multi-App Run

Step 6: View the Service Invocation outputs

Step 1: Pre-requisites

Step 2: Set up the environment

Step 3: Run order-processor service

Step 4: Run checkout service

Step 5: Use with Multi-App Run

Step 6: View the Service Invocation outputs

Step 1: Pre-requisites

Step 2: Set up the environment

Step 3: Run order-processor service

Step 4: Run checkout service

Step 5: Use with Multi-App Run

Step 6: View the Service Invocation outputs

Step 1: Pre-requisites

Step 2: Set up the environment

Step 3: Run order-processor service

Step 4: Run checkout service

Step 5: Use with Multi-App Run

Step 6: View the Service Invocation outputs

Tell us what you think!

Next Steps

Step 3: Run `order-processor` service

Step 4: Run `checkout` service

Step 3: Run `order-processor` service

Step 4: Run `checkout` service

Step 3: Run `order-processor` service

Step 4: Run `checkout` service

Step 3: Run `order-processor` service

Step 4: Run `checkout` service

Step 3: Run `order-processor` service

Step 4: Run `checkout` service