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.

Diagram showing the steps of service invocation

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.


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 7001 --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=7001)

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: 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

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.

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: 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/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
app.MapPost("/orders", async context => {
    var data = await context.Request.ReadFromJsonAsync<Order>();
    Console.WriteLine("Order received : " + data);
    await context.Response.WriteAsync(data.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 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: 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: 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:

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

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.

.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: 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: 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 app.go

Run the checkout service alongside a Dapr sidecar.

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

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.

req.Header.Add("dapr-app-id", "order-processor")

response, err := client.Do(req)

Step 5: 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}

Tell us what you think!

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Last modified September 28, 2022: Upmerge v1.8 --> v1.9 - 9/28 (#2839) (9286e093)