Prerequisites

To complete this part of the guide, you need:

1. Latest Ballerina Swan Lake distribution
2. A text editor

   Tip: Preferably, Visual Studio Code with the Ballerina extension installed.

3. Docker installed and configured in your machine

   Tip: Since the GraalVM native build consumes a significant amount of memory, it is recommended to increase the memory allocated to Docker to at least 8GB and potentially add more CPUs as well. For more details, see How to assign more memory to Docker container.

4. A command terminal

After the environment is set up, follow the steps below to build the native executable and pack it in a container.

Build the GraalVM executable in a container

1. Execute the command below to create a Ballerina service package.

   $ bal new hello_docker -t service
   

2. Replace the content of the file service.bal with the following.

   import ballerina/http;
   
   service / on new http:Listener(8080) {
       resource function get greeting() returns string {   
           return "Hello, Docker!";   
       }
   }

3. Execute bal build --graalvm --cloud=docker to generate the artifacts with the native executable.

   Info: Optionally, you can create a file named Cloud.toml in the package directory to add cloud related configurations. For more information, see Docker and Kubernetes documentation.

   $ bal build --graalvm --cloud=docker
   Compiling source
           user/hello_docker:0.1.0
   
   Generating artifacts
   Building the native image. This may take a while
   
   [+] Building 193.8s (13/13) FINISHED                                                                                                                                        docker:default
    => [internal] load .dockerignore                                                                                              0.0s
    => => transferring context: 2B                                                                                                0.0s
    => [internal] load build definition from Dockerfile                                                                           0.0s
    => => transferring dockerfile: 416B                                                                                           0.0s
    => [internal] load metadata for gcr.io/distroless/base:latest                                                                 3.2s
    => [internal] load metadata for ghcr.io/graalvm/native-image-community:17-ol8                                                 4.2s
    => [build 1/4] FROM ghcr.io/graalvm/native-image-community:17-ol8@sha256                                                      0.0s
    => [internal] load build context                                                                                              0.2s
    => => transferring context: 38.38MB                                                                                           0.2s
    => [stage-1 1/3] FROM gcr.io/distroless/base@sha256:73deaaf6a207c1a33850257ba74e0f196bc418636cada9943a03d7abea980d6d          0.0s
    => CACHED [stage-1 2/3] WORKDIR /home/ballerina                                                                               0.0s
    => CACHED [build 2/4] WORKDIR /app/build                                                                                      0.0s
    => [build 3/4] COPY hello_world.jar .                                                                                         0.1s
    => [build 4/4] RUN native-image -jar hello_world.jar -H:Name=hello_world --no-fallback -H:+StaticExecutableWithDynamicLibC  188.7s
    => [stage-1 3/3] COPY --from=build /app/build/hello_world .                                                                   0.2s 
    => exporting to image                                                                                                         0.3s 
    => => exporting layers                                                                                                        0.2s 
    => => writing image sha256:0129932fea465e620849b5842b42cb8136ab2daabf25e1817a7879207f6d861b                                   0.0s 
    => => naming to docker.io/library/hello_world:latest                                                                          0.0s 
                                                                                                                                                                                           
    Execute the below command to run the generated Docker image: 
           docker run -d -p 8080:8080 hello_world:latest
   

   The Docker file:

   # Auto Generated Dockerfile
   FROM ghcr.io/graalvm/native-image-community:17-ol8 as build
   
   WORKDIR /app/build
   
   COPY hello_world.jar .
   
   RUN native-image -jar hello_world.jar -H:Name=hello_world --no-fallback -H:+StaticExecutableWithDynamicLibC
   
   FROM gcr.io/distroless/base
   
   WORKDIR /home/ballerina
   
   EXPOSE  8080
   COPY --from=build /app/build/hello_world .
   
   CMD ["./hello_world"]
   

4. Execute the Docker image.

   $ docker run -d -p 8080:8080 hello_docker:latest
   

5. Test the service with the cURL request below.

   $ curl http://localhost:8080/greeting
   Hello, Docker!