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Alpaquita Linux23Containers
Build Applications With Buildpacks
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Alpaquita Linux: Building Java applications with Cloud Native Buildpacks

1. Introduction

BellSoft provides Cloud Native Buildpacks images that contain the latest versions of Liberica JDK Lite and Liberica NIK products specifically built and optimized for Alpaquita Linux. Alpaquita Linux is a full-featured operating system shipped in two libc variants based on two different libc implementations, namely glibc and musl. BellSoft provides images for both glibc and musl libc libraries.

Using Alpaquita Linux (musl) as a target image helps you create lightweight Docker images. For example, the size of a Docker image for a basic Spring Boot application running Java 21, if using standard paketobuildpacks/builder-jammy-tiny is about 250 MB, while using bellsoft/buildpacks.builder:musl saves about 140 MB.

Cloud Native Buildpacks

Cloud Native Buildpacks (CNBs) transform your application source code into container images that can run on any cloud.

Liberica JDK Lite

Liberica JDK Lite is a JDK optimized for cloud instances with a minimal footprint. It is a full-fledged, Java SE-compliant runtime but much smaller than any standard Java distribution. Liberica JDK Lite has a higher compression ratio for modules than a classic JDK, thus reducing static footprint. For more information, see Liberica JDK Lite in the Choosing Liberica JDK flavor document.

Liberica NIK

Liberica Native Image Kit is a utility capable of converting your JVM-based application into a fully compiled native executable ahead-of-time under the closed-world assumption with an almost instant startup time. It optimizes resource consumption, minimizes the static footprint, and works on various platforms, including lightweight musl-based Alpaquita Linux.

2. Image flavors

When building images from BellSoft buildpacks, you can choose one of the latest JDK releases of 8, 11, 17 (default), and 21 JDK versions; 22 and 23 NIK versions as well as Alpaquita Linux based on glibc and musl libraries. For the latest product release versions, see the following links:

Choosing libc library

If the size of the resulting image is important and the final application does not have native components that require glibc, then choose musl. If you need higher performance with a slight increase in size of the final image, it makes sense to consider using the glibc library. In addition, there might be other considerations when choosing C runtime, such as licensing.

3. Building a Java application with Alpaquita Linux

To build a Java application for Alpaquita Linux with the default JDK version, run one of the following commands within the root of your project. Make sure you choose the bellsoft builder and specify the target C library.

Note:
 A builder includes the buildpacks that will be used as well as the environment for building your app. For more information about getting started with buildpacks, see Build your very first application with buildpacks.

  • Building a Java application with Alpaquita Linux (glibc)

    pack build demo-app --builder bellsoft/buildpacks.builder:glibc --path .

  • Building a Java application with Alpaquita Linux (musl)

    pack build demo-app --builder bellsoft/buildpacks.builder:musl --path .

Where bellsoft/buildpacks.builder:<glibc/musl> is the BellSoft builder producing an Alpaquita Linux image with the specified C library. You can also specify BellSoft builder as the default one as follows:

pack config default-builder bellsoft/buildpacks.builder:musl

If you want to install a specific JVM feature version, use the BP_JVM_VERSION environment variable that accepts the following JDK version values: 8, 11, 17, 21 (default is 17). For example:

pack build demo-app --builder bellsoft/buildpacks.builder:glibc --path . -env BP_JVM_VERSION=21

To inspect the resulting image, check the stack, buildpacks participated in the build, etc. Run the following command:

pack inspect demo-app

You can also check the Linux distro inside your Docker image as follows:

docker run --rm -it --entrypoint /bin/cat demo-app /etc/os-release

Then you can check the image size as follows:

docker image ls demo-app

To run the application, use the following Docker command:

docker run --rm -it demo-app

The JRE inside the resulting image can be optimized in size by using the jlink tool. To enable jlink, set the environment variable BP_JVM_JLINK_ENABLED to true (default is false). In this case, jlink generates a custom JRE with the following default options: --no-man-pages, --no-header-files, --strip-debug, --compress=1. To change the options, use BP_JVM_JLINK_ARGS environment variable. Check the jlink documentation for further information.

For example, the following command creates a new application image on Alpaquita Linux with a custom JRE 21:

pack build demo-app --builder bellsoft/buildpacks.builder:musl --path . -env BP_JVM_VERSION=21 -env BP_JVM_JLINK_ENABLED=true

The resulting image is usually smaller than the one with the default JRE.

5. Building native image

To build the native image application, set the BP_NATIVE_IMAGE environment variable to true as in the following example:

pack -v build demo-native-app --builder bellsoft/buildpacks.builder:musl --path . --env BP_NATIVE_IMAGE=true --env BP_JVM_VERSION=21

You can check the size of the resulting image as follows:

docker image ls demo-native-app

To run the application, use the following Docker command:

docker run --rm -it demo-native-app

6. Configuration options

The following table lists pack builder configuration options for BellSoft Liberica JDK Lite and Native Image Kit Cloud Native Buildpacks ver. 1.1.0.

VariableDefault valueDescription

Build configuration options

$BP_JVM_JLINK_ARGS

  • --no-man-pages

  • --no-header-files

  • --strip-debug

  • --compress=1

Configures custom jlink arguments (--output must be omitted).

$BP_JVM_JLINK_ENABLED

false

Enables the jlink tool to generate custom JRE.

$BP_JVM_TYPE

JRE

Specifies the JVM type - JDK or JRE.

$BP_JVM_VERSION

17

Specifies a Java version.

Launch configuration options

$BPL_DEBUG_ENABLED

false

Enables Java remote debugging support.

$BPL_DEBUG_PORT

8000

Specifies the remote debugging port.

$BPL_DEBUG_SUSPEND

false

Specifies whether to suspend execution until a debugger has attached.

$BPL_HEAP_DUMP_PATH

N/A

Specifies the path to write heap dumps on error.

$BPL_JAVA_NMT_ENABLED

true

Enables Java Native Memory Tracking (NMT).

$BPL_JAVA_NMT_LEVEL

summary

Configures the level of NMT, summary or detail.

$BPL_JFR_ARGS

N/A

Configures custom Java Flight Recording (JFR) arguments.

$BPL_JFR_ENABLED

false

Enables Java Flight Recorder (JFR).

$BPL_JMX_ENABLED

false

Enables Java Management Extensions (JMX).

$BPL_JMX_PORT

5000

Specifies the JMX port.

$BPL_JVM_HEAD_ROOM

0

Configures the headroom in memory calculation.

$BPL_JVM_LOADED_CLASS_COUNT

35% of classes

Sets the number of loaded classes in memory calculation.

$BPL_JVM_THREAD_COUNT

250

Sets the number of threads in memory calculation.

$JAVA_TOOL_OPTIONS

N/A

Specifies the JVM launch flags.

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