From 437f770b1f0de52dd8431caaf2f0d04de2fcfafb Mon Sep 17 00:00:00 2001
From: Gunnar von der Beck <Gunnar.von-der-Beck@accso.de>
Date: Wed, 30 Aug 2023 14:34:45 +0200
Subject: [PATCH] chore: shrink docker image using adoptium buildpack with
 jlink enabled

---
 examples/sso-kubernetes/README.md | 10 ++++++++++
 examples/sso-kubernetes/pom.xml   | 13 +++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/examples/sso-kubernetes/README.md b/examples/sso-kubernetes/README.md
index f5b5d14f..87c98783 100644
--- a/examples/sso-kubernetes/README.md
+++ b/examples/sso-kubernetes/README.md
@@ -339,6 +339,16 @@ Finally - a quick introduction on how to setup Keycloak and this showcase on Kub
 
 Before we turn to Kubernetes it is necessary to build the Docker image. As we included the ``spring-boot-maven-plugin`` everything is quite simple, just run ``mvn spring-boot:build-image``.
 
+The Docker Image Build is using the `gcr.io/paketo-buildpacks/adoptium` Buildpack having JDK's jlink tool at build time enabled to generate a custom slim JRE.
+
+#### Java module dependencies & jlinked Java 17
+
+Just for the records - how to find out java module dependencies and shrink your JRE:
+* Extract ``target/camunda-platform-7-keycloak-examples-sso-kubernetes.jar/BOOT-INF/lib`` to `target/lib``
+* Open a shell in ``target`` and run ``jdeps -cp lib/* -R --multi-release 17 --print-module-deps --ignore-missing-deps camunda-platform-7-keycloak-examples-sso-kubernetes.jar``
+
+The result goes to the jlink `add-modules` option in the `BP_JVM_JLINK_ARGS` environment parameter of the `spring-boot-maven-plugin` image configuration.
+
 ### Kubernetes
 
 The Kubernetes setup can be found in directory ``k8s``. It contains a subfolder ``keycloak`` setting up the Keycloak test server.
diff --git a/examples/sso-kubernetes/pom.xml b/examples/sso-kubernetes/pom.xml
index cbb02cd4..f44b4fbd 100644
--- a/examples/sso-kubernetes/pom.xml
+++ b/examples/sso-kubernetes/pom.xml
@@ -16,7 +16,6 @@
 	<properties>
 		<failOnMissingWebXml>false</failOnMissingWebXml>
 
-		<docker.buildPack>paketobuildpacks/builder-jammy-tiny</docker.buildPack>
 		<docker.imageName>gunnaraccso/camunda-showcase-keycloak:${version}</docker.imageName>
 	</properties>
 
@@ -158,7 +157,17 @@
 						<enabled>true</enabled>
 					</layers>
 					<image>
-						<builder>${docker.buildPack}</builder>
+						<builder>paketobuildpacks/builder:tiny</builder>
+						<buildpacks>
+							<buildpack>gcr.io/paketo-buildpacks/adoptium</buildpack>
+							<buildpack>paketo-buildpacks/java</buildpack>
+						</buildpacks>
+						<env>
+							<BP_JVM_VERSION>${version.java}</BP_JVM_VERSION>
+							<BP_JVM_TYPE>JRE</BP_JVM_TYPE>
+							<BP_JVM_JLINK_ENABLED>true</BP_JVM_JLINK_ENABLED>
+							<BP_JVM_JLINK_ARGS>--no-man-pages --no-header-files --strip-debug --compress=2 --add-modules java.base,java.compiler,java.desktop,java.instrument,java.net.http,java.prefs,java.rmi,java.scripting,java.security.jgss,java.security.sasl,java.sql.rowset,jdk.attach,jdk.jdi,jdk.jfr,jdk.management,jdk.net,jdk.unsupported</BP_JVM_JLINK_ARGS>
+						</env>
 					</image>
 					<imageName>${docker.imageName}</imageName>
 				</configuration>