Kubernetes(K8s) Helidon App

Cowsay Web API.

• Build and run
• Exercise the application
• Try metrics
  • (option) Grafana Dashboard
• Try health
• Building a Native Image
• Building the Docker Image
• Running the Docker Image
• Building a Custom Runtime Image

Build and run

With JDK20+

./mvnw package
java --enable-preview -jar target/cowweb-helidon.jar

Exercise the application

cowsay's say.

curl -X GET http://localhost:8080/cowsay/say
 ______
< Moo! >
 ------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

curl -X GET http://localhost:8080/cowsay/say?say=Hello
 _______
< Hello >
 -------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

curl -X GET http://localhost:8080/cowsay/say?say=Wow!&cowfile=www
 _______
< Wow! >
 -------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||--WWW |
                ||     ||

cowsay's think.

curl -X GET http://localhost:8080/cowsay/think
 ______
( Moo! )
 ------
        o   ^__^
         o  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

curl -X GET http://localhost:8080/cowsay/think?think=Hello
 _______
( Hello )
 -------
        o   ^__^
         o  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

curl -X GET http://localhost:8080/cowsay/think?think=Wow!&cowfile=www
 ______
( Wow! )
 ------
        o   ^__^
         o  (oo)\_______
            (__)\       )\/\
                ||--WWW |
                ||     ||

Try metrics

# Prometheus Format
curl -s -X GET http://localhost:8080/metrics
# TYPE base:gc_g1_young_generation_count gauge
. . .

# JSON Format
curl -H 'Accept: application/json' -X GET http://localhost:8080/metrics
{"base":...
. . .

(option) Grafana Dashboard

Import grafana/helidon-dashboard.json into Grafana(running on K8s w/ Prometheus). You can see metrics.

Try health

curl -s -X GET http://localhost:8080/health
{"status":"UP","checks":[]}

Building a Native Image

Make sure you have GraalVM locally installed:

$GRAALVM_HOME/bin/native-image --version

Build the native image using the native image profile:

./mvnw package -Pnative-image

This uses the helidon-maven-plugin to perform the native compilation using your installed copy of GraalVM. It might take a while to complete. Once it completes start the application using the native executable (no JVM!):

./target/cowweb-helidon

Yep, it starts fast. You can exercise the application’s endpoints as before.

Building the Docker Image

docker build -t cowweb-helidon .

Running the Docker Image

docker run --rm -p 8080:8080 cowweb-helidon:latest

Exercise the application as described above.

Building a Custom Runtime Image

Build the custom runtime image using the jlink image profile:

./mvn package -Pjlink-image

This uses the helidon-maven-plugin to perform the custom image generation. After the build completes it will report some statistics about the build including the reduction in image size.

The target/cowweb-helidon-jri directory is a self contained custom image of your application. It contains your application, its runtime dependencies and the JDK modules it depends on. You can start your application using the provide start script:

./target/cowweb-helidon-jri/bin/start

Class Data Sharing (CDS) Archive Also included in the custom image is a Class Data Sharing (CDS) archive that improves your application’s startup performance and in-memory footprint. You can learn more about Class Data Sharing in the JDK documentation.

The CDS archive increases your image size to get these performance optimizations. It can be of significant size (tens of MB). The size of the CDS archive is reported at the end of the build output.

If you’d rather have a smaller image size (with a slightly increased startup time) you can skip the creation of the CDS archive by executing your build like this:

./mvn package -Pjlink-image -Djlink.image.addClassDataSharingArchive=false

For more information on available configuration options see the helidon-maven-plugin documentation.