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title services ms.date ms.topic description keywords
Running multiple dependent services: Java & Visual Studio Code
azure-dev-spaces
11/21/2018
tutorial
This tutorial shows you how to use Azure Dev Spaces and Visual Studio Code to debug a multi-service Java application on Azure Kubernetes Service
Docker, Kubernetes, Azure, AKS, Azure Kubernetes Service, containers, Helm, service mesh, service mesh routing, kubectl, k8s

Running multiple dependent services: Java and Visual Studio Code with Azure Dev Spaces

In this tutorial, you'll learn how to develop multi-service applications using Azure Dev Spaces, along with some of the added benefits that Dev Spaces provides.

Call a service running in a separate container

In this section, you create a second service, mywebapi, and have webfrontend call it. Each service will run in separate containers. You'll then debug across both containers.

Multiple containers

Download sample code for mywebapi

For the sake of time, let's download sample code from a GitHub repository. Go to https://github.com/Azure/dev-spaces and select Clone or Download to download the GitHub repository. The code for this section is in samples/java/getting-started/mywebapi.

Run mywebapi

  1. Open the folder mywebapi in a separate VS Code window.

  2. Open the Command Palette (using the View | Command Palette menu), and use auto-complete to type and select this command: Azure Dev Spaces: Prepare configuration files for Azure Dev Spaces.

  3. Hit F5, and wait for the service to build and deploy. You'll know it's ready when a message similar to the below appears in the debug console:

    2019-03-11 17:02:35.935  INFO 216 --- [           main] com.ms.sample.mywebapi.Application       : Started Application in 8.164 seconds (JVM running for 9.272)

  4. The endpoint URL will look something like http://localhost:<portnumber>. Tip: The VS Code status bar will turn orange and display a clickable URL. It might seem like the container is running locally, but actually it is running in our dev space in Azure. The reason for the localhost address is because mywebapi has not defined any public endpoints and can only be accessed from within the Kubernetes instance. For your convenience, and to facilitate interacting with the private service from your local machine, Azure Dev Spaces creates a temporary SSH tunnel to the container running in Azure.

  5. When mywebapi is ready, open your browser to the localhost address.

  6. If all the steps were successful, you should be able to see a response from the mywebapi service.

Make a request from webfrontend to mywebapi

Let's now write code in webfrontend that makes a request to mywebapi.

  1. Switch to the VS Code window for webfrontend.

  2. Add the following import statements under the package statement:

    import java.io.*;
import java.net.*;

  3. Replace the code for the greeting method:

    @RequestMapping(value = "/greeting", produces = "text/plain")
public String greeting(@RequestHeader(value = "azds-route-as", required = false) String azdsRouteAs) throws Exception {
    URLConnection conn = new URL("http://mywebapi/").openConnection();
    conn.setRequestProperty("azds-route-as", azdsRouteAs); // propagate dev space routing header
    try (BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream())))
    {
        return "Hello from webfrontend and " + reader.lines().reduce("\n", String::concat);
    }
}

The preceding code example forwards the azds-route-as header from the incoming request to the outgoing request. You'll see later how this helps teams with collaborative development.

Debug across multiple services

  1. At this point, mywebapi should still be running with the debugger attached. If it is not, hit F5 in the mywebapi project.
  2. Set a breakpoint in the index() method of the mywebapi project, on line 19 of Application.java
  3. In the webfrontend project, set a breakpoint just before it sends a GET request to mywebapi, on the line starting with try.
  4. Hit F5 in the webfrontend project (or restart the debugger if currently running).
  5. Invoke the web app, and step through code in both services.
  6. In the web app, the About page will display a message concatenated by the two services: "Hello from webfrontend and Hello from mywebapi."

Well done!

You now have a multi-container application where each container can be developed and deployed separately.

Next steps

[!div class="nextstepaction"] Learn about team development in Dev Spaces