How-To: Invoke services using HTTP

Call between services using service invocation

This article demonstrates how to deploy services each with an unique application ID for other services to discover and call endpoints on them using service invocation over HTTP.

Diagram showing service invocation of example service

For a complete sample demonstrating service invocation, walk through the service invocation quickstart.

Choose an ID for your service

Dapr allows you to assign a global, unique ID for your app. This ID encapsulates the state for your application, regardless of the number of instances it may have.

  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 dotnet run
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 dotnet run

If your app uses an SSL connection, you can tell Dapr to invoke your app over an insecure SSL connection:

  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --app-ssl dotnet run
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --app-ssl dotnet run
  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 mvn spring-boot:run
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 mvn spring-boot:run

If your app uses an SSL connection, you can tell Dapr to invoke your app over an insecure SSL connection:

  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --app-ssl mvn spring-boot:run
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --app-ssl mvn spring-boot:run
  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 -- python3 CheckoutService.py
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 -- python3 OrderProcessingService.py

If your app uses an SSL connection, you can tell Dapr to invoke your app over an insecure SSL connection:

  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --app-ssl -- python3 CheckoutService.py
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --app-ssl -- python3 OrderProcessingService.py
  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 go run CheckoutService.go
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 go run OrderProcessingService.go

If your app uses an SSL connection, you can tell Dapr to invoke your app over an insecure SSL connection:

  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --app-ssl go run CheckoutService.go
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --app-ssl go run OrderProcessingService.go
  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 npm start
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 npm start

If your app uses an SSL connection, you can tell Dapr to invoke your app over an insecure SSL connection:

  1. dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --app-ssl npm start
  2. dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --app-ssl npm start

Set an app-id when deploying to Kubernetes

In Kubernetes, set the dapr.io/app-id annotation on your pod:

  1. apiVersion: apps/v1
  2. kind: Deployment
  3. metadata:
  4. name: <language>-app
  5. namespace: default
  6. labels:
  7. app: <language>-app
  8. spec:
  9. replicas: 1
  10. selector:
  11. matchLabels:
  12. app: <language>-app
  13. template:
  14. metadata:
  15. labels:
  16. app: <language>-app
  17. annotations:
  18. dapr.io/enabled: "true"
  19. dapr.io/app-id: "orderprocessingservice"
  20. dapr.io/app-port: "6001"
  21. ...

If your app uses an SSL connection, you can tell Dapr to invoke your app over an insecure SSL connection with the app-ssl: "true" annotation (full list here)

Invoke the service

To invoke an application using Dapr, you can use the invoke API on any Dapr instance. The sidecar programming model encourages each application to interact with its own instance of Dapr. The Dapr sidecars discover and communicate with one another.

Below are code examples that leverage Dapr SDKs for service invocation.

  1. //dependencies
  2. using System;
  3. using System.Collections.Generic;
  4. using System.Net.Http;
  5. using System.Net.Http.Headers;
  6. using System.Threading.Tasks;
  7. using Dapr.Client;
  8. using Microsoft.AspNetCore.Mvc;
  9. using System.Threading;
  10. //code
  11. namespace EventService
  12. {
  13. class Program
  14. {
  15. static async Task Main(string[] args)
  16. {
  17. while(true) {
  18. System.Threading.Thread.Sleep(5000);
  19. Random random = new Random();
  20. int orderId = random.Next(1,1000);
  21. CancellationTokenSource source = new CancellationTokenSource();
  22. CancellationToken cancellationToken = source.Token;
  23. using var client = new DaprClientBuilder().Build();
  24. //Using Dapr SDK to invoke a method
  25. var result = client.CreateInvokeMethodRequest(HttpMethod.Get, "checkout", "checkout/" + orderId, cancellationToken);
  26. await client.InvokeMethodAsync(result);
  27. Console.WriteLine("Order requested: " + orderId);
  28. Console.WriteLine("Result: " + result);
  29. }
  30. }
  31. }
  32. }
  1. //dependencies
  2. import io.dapr.client.DaprClient;
  3. import io.dapr.client.DaprClientBuilder;
  4. import io.dapr.client.domain.HttpExtension;
  5. import org.springframework.boot.autoconfigure.SpringBootApplication;
  6. import org.slf4j.Logger;
  7. import org.slf4j.LoggerFactory;
  8. import java.util.Random;
  9. import java.util.concurrent.TimeUnit;
  10. //code
  11. @SpringBootApplication
  12. public class OrderProcessingServiceApplication {
  13. private static final Logger log = LoggerFactory.getLogger(OrderProcessingServiceApplication.class);
  14. public static void main(String[] args) throws InterruptedException{
  15. while(true) {
  16. TimeUnit.MILLISECONDS.sleep(5000);
  17. Random random = new Random();
  18. int orderId = random.nextInt(1000-1) + 1;
  19. DaprClient daprClient = new DaprClientBuilder().build();
  20. //Using Dapr SDK to invoke a method
  21. var result = daprClient.invokeMethod(
  22. "checkout",
  23. "checkout/" + orderId,
  24. null,
  25. HttpExtension.GET,
  26. String.class
  27. );
  28. log.info("Order requested: " + orderId);
  29. log.info("Result: " + result);
  30. }
  31. }
  32. }
  1. #dependencies
  2. import random
  3. from time import sleep
  4. import logging
  5. from dapr.clients import DaprClient
  6. #code
  7. logging.basicConfig(level = logging.INFO)
  8. while True:
  9. sleep(random.randrange(50, 5000) / 1000)
  10. orderId = random.randint(1, 1000)
  11. with DaprClient() as daprClient:
  12. #Using Dapr SDK to invoke a method
  13. result = daprClient.invoke_method(
  14. "checkout",
  15. f"checkout/{orderId}",
  16. data=b'',
  17. http_verb="GET"
  18. )
  19. logging.basicConfig(level = logging.INFO)
  20. logging.info('Order requested: ' + str(orderId))
  21. logging.info('Result: ' + str(result))
  1. //dependencies
  2. import (
  3. "context"
  4. "log"
  5. "math/rand"
  6. "time"
  7. "strconv"
  8. dapr "github.com/dapr/go-sdk/client"
  9. )
  10. //code
  11. type Order struct {
  12. orderName string
  13. orderNum string
  14. }
  15. func main() {
  16. for i := 0; i < 10; i++ {
  17. time.Sleep(5000)
  18. orderId := rand.Intn(1000-1) + 1
  19. client, err := dapr.NewClient()
  20. if err != nil {
  21. panic(err)
  22. }
  23. defer client.Close()
  24. ctx := context.Background()
  25. //Using Dapr SDK to invoke a method
  26. result, err := client.InvokeMethod(ctx, "checkout", "checkout/" + strconv.Itoa(orderId), "get")
  27. log.Println("Order requested: " + strconv.Itoa(orderId))
  28. log.Println("Result: ")
  29. log.Println(result)
  30. }
  31. }
  1. //dependencies
  2. import { DaprClient, HttpMethod, CommunicationProtocolEnum } from 'dapr-client';
  3. //code
  4. const daprHost = "127.0.0.1";
  5. var main = function() {
  6. for(var i=0;i<10;i++) {
  7. sleep(5000);
  8. var orderId = Math.floor(Math.random() * (1000 - 1) + 1);
  9. start(orderId).catch((e) => {
  10. console.error(e);
  11. process.exit(1);
  12. });
  13. }
  14. }
  15. async function start(orderId) {
  16. const client = new DaprClient(daprHost, process.env.DAPR_HTTP_PORT, CommunicationProtocolEnum.HTTP);
  17. //Using Dapr SDK to invoke a method
  18. const result = await client.invoker.invoke('checkoutservice' , "checkout/" + orderId , HttpMethod.GET);
  19. console.log("Order requested: " + orderId);
  20. console.log("Result: " + result);
  21. }
  22. function sleep(ms) {
  23. return new Promise(resolve => setTimeout(resolve, ms));
  24. }
  25. main();

Additional URL formats

To invoke a ‘GET’ endpoint:

  1. curl http://localhost:3602/v1.0/invoke/checkout/method/checkout/100

To avoid changing URL paths as much as possible, Dapr provides the following ways to call the service invocation API:

  1. Change the address in the URL to localhost:<dapr-http-port>.
  2. Add a dapr-app-id header to specify the ID of the target service, or alternatively pass the ID via HTTP Basic Auth: http://dapr-app-id:<service-id>@localhost:3602/path.

For example, the following command:

  1. curl http://localhost:3602/v1.0/invoke/checkout/method/checkout/100

is equivalent to:

  1. curl -H 'dapr-app-id: checkout' 'http://localhost:3602/checkout/100' -X POST

or:

  1. curl 'http://dapr-app-id:checkout@localhost:3602/checkout/100' -X POST

Using CLI:

  1. dapr invoke --app-id checkout --method checkout/100

Namespaces

When running on namespace supported platforms, you include the namespace of the target app in the app ID: checkout.production

For example, invoking the example service with a namespace would look like:

  1. curl http://localhost:3602/v1.0/invoke/checkout.production/method/checkout/100 -X POST

See the Cross namespace API spec for more information on namespaces.

View traces and logs

Our example above showed you how to directly invoke a different service running locally or in Kubernetes. Dapr:

  • Outputs metrics, tracing, and logging information,
  • Allows you to visualize a call graph between services and log errors, and
  • Optionally, log the payload body.

For more information on tracing and logs, see the observability article.

Last modified June 23, 2022: Merge pull request #2550 from ItalyPaleAle/cosmosdb-harcoded-dapr-version (cf03237)