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getting_started_java.md

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Getting Started: OSv on Java Edition!

In this tutorial we'll be:

  1. installing UniK
  2. writing a simple HTTP Daemon in Java
  3. compiling to a unikernel and launching an instance on Virtualbox

Installing UniK

Prerequisites

Ensure that each of the following are installed

Install, configure, and launch UniK

  1. Install UniK
$ git clone https://github.com/solo-io/unik.git
$ cd unik
$ make

note: make will take quite a few minutes the first time it runs. the UniK Makefile is pulling all of the Docker images that bundle UniK's dependencies.

Then, place the unik executable in your $PATH to make running UniK commands easier:

$ mv _build/unik /usr/local/bin/
  1. Configure a Host-Only Network on Virtualbox
  • Open Virtualbox
  • Open Preferences > Network > Host-only Networks
  • Click the green add button on the right side of the UI
  • Record the name of the new Host-Only adapter. You will need this in your UniK configuration
  • Ensure that the Virtualbox DHCP Server is Enabled for this Host-Only Network:
    • With the Host-Only Network selected, Click the edit button (screwdriver image)
    • In the Adapter tab, note the IPv4 address and netmask of the adapter.
    • In the DHCP Server tab, check the Enable Server box
    • Set Server Address an IP on the same subnet as the Adapter IP. For example, if the adapter IP is 192.168.100.1, make set the DHCP server IP as 192.168.100.X, where X is a number between 2-254.
    • Set Server Mask to the netmask you just noted
    • Set Upper / Lower Address Bound to a range of IPs on the same subnet. We recommend using the range X-254 where X is one higher than the IP you used for the DHCP server itself. E.g., if your DHCP server is 192.168.100.2, you can set the lower and upper bounds to 192.168.100.3 and 192.168.100.254, respectively.
  1. Configure UniK daemon
  • Using a text editor, create and save the following to $HOME/.unik/daemon-config.yaml:
providers:
  virtualbox:
    - name: my-vbox
      adapter_type: host_only
      adapter_name: NEW_HOST_ONLY_ADAPTER

replacing NEW_HOST_ONLY_ADAPTER with the name of the network adapter you created.

  1. Launch UniK and automatically deploy the Virtualbox Instance Listener
  • Open a new terminal window/tab. This terminal will be where we leave the UniK daemon running.
  • cd to the _build directory created by make
  • run ./unik daemon --debug (the --debug flag is optional, if you want to see more verbose output)
  • UniK will compile and deploy its own 30 MB unikernel. This unikernel is the Unik Instance Listener. The instance listener uses udp broadcast to detect instance ips and bootstrap instances running on Virtualbox.
  • After this is finished, UniK is running and ready to accept commands.
  • Open a new terminal window and type unik target --host localhost to set the CLI target to the your local machine.

Write a Java HTTP server using Maven

  1. Open a new terminal window, but leave the window with the daemon running. This window will be used for running UniK CLI commands.
  2. mkdir a new directory to create this sample app in & cd to it.
  3. Generate a new maven project with the following command:
mvn -B archetype:generate \
  -DarchetypeGroupId=org.apache.maven.archetypes \
  -DgroupId=com.mycompany.app \
  -DartifactId=my-app

Great! we've got the project structure created. Let's cd into the new project folder my-app.

  1. We need to add a plugin to our project's pom.xml so it can be built as a fat jar (all dependencies packaged into one .jar file):
  • Add the maven-assembly-plugin between the <plugins>...</plugins> tags:
<plugins>
       <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-assembly-plugin</artifactId>
          <version>2.2-beta-4</version>
          <configuration>
            <descriptorRefs>
              <descriptorRef>jar-with-dependencies</descriptorRef>
            </descriptorRefs>
            <archive>
              <manifest>
                <mainClass>com.mycompany.app.App</mainClass>
              </manifest>
            </archive>
          </configuration>
          <executions>
            <execution>
              <phase>package</phase>
              <goals>
                <goal>single</goal>
              </goals>
            </execution>
          </executions>
       </plugin>
</plugins>
  • Now our application is UniK-ready. Let's add some code to our App.java source file. Open up src/main/java/com/mycompany/app/App.java and replace its contents with the following:
  package com.mycompany.app;

  import java.io.IOException;
  import java.io.OutputStream;
  import java.net.InetSocketAddress;

  import com.sun.net.httpserver.HttpExchange;
  import com.sun.net.httpserver.HttpHandler;
  import com.sun.net.httpserver.HttpServer;

  public class App
  {
    public static void main(String[] args) throws Exception {
        System.out.println("Started!");
        HttpServer server = HttpServer.create(new InetSocketAddress(4000), 0);
        server.createContext("/", new MyHandler());
        server.setExecutor(null); // creates a default executor
        server.start();
    }

    static class MyHandler implements HttpHandler {
        @Override
        public void handle(HttpExchange t) throws IOException {
            String response = "Java running inside a unikernel!";
            t.sendResponseHeaders(200, response.length());
            OutputStream os = t.getResponseBody();
            os.write(response.getBytes());
            os.close();
        }
    }
  }

  1. If you have Java installed, you can try running this code with mvn package && java -jar target/my-app-1.0-SNAPSHOT-jar-with-dependencies.jar. Visit http://localhost:4000/ to see that the server is running.

  2. We have to add a manifest file to tell unik how to build our application into a unikernel. Create a file named manifest.yaml in the same directory as the pom.xml (the java project root) and paste the following inside:

main_file: target/my-app-1.0-SNAPSHOT-jar-with-dependencies.jar
build_command: mvn package

This will tell UniK to build our project with the mvn package commmand, and that the resulting jar file will be located at target/my-app-1.0-SNAPSHOT-jar-with-dependencies.jar.

  1. Great! Now we're ready to compile this code to a unikernel.

Compile an image and run on Virtualbox

  1. Make sure that the UniK daemon is still running, and run the following:
unik build --name myJavaImage --path PATH_TO_JAVA_PROJECT --base osv --language java --provider virtualbox

Replacing PATH_TO_JAVA_PROJECT with the path to the root of the java project we created. (This will be the directory containing the pom.xml file). 2. You can watch the output of the build command in the terminal window running the daemon. 3. When build finishes, the resulting disk image will exist as a virtual disk image in your $HOME/.unik directory. 4. Run an instance of this image with

unik run --instanceName myJavaInstance --imageName myJavaImage
  1. When the instance finishes launching, let's check its IP and see that it is running our application.
  2. Run unik instances. The instance IP Address should be listed.
  3. Direct your browser to http://instance-ip:4000 and see that your instance is running!
  4. To clean up your image and the instance you created
unik rmi --force --image myImage