fix: Resolve any missing shared library bug in the final image & switch to jetty to have a smaller footprint

Author: emre.akkaya

Dockerfile

@@ -34,15 +34,22 @@ RUN set -eux; \
     deps="$(jdeps --ignore-missing-deps --multi-release ${JAVA_VERSION} \
         --print-module-deps app.jar)"; \
     jlink --strip-debug --no-man-pages --no-header-files --compress=2 \
-        --add-modules "${deps},jdk.unsupported" \
-        --output /opt/jre
+        --add-modules "${deps},jdk.unsupported,java.desktop,java.management,java.logging,java.naming,java.instrument,jdk.crypto.ec" \
+        --output /opt/jre; \
+    mkdir -p /opt/runtime-libs; \
+    for bin in /opt/jre/bin/java /opt/jre/lib/server/libjvm.so; do \
+        ldd "$bin" \
+        | awk '/=>/ {print $3} /^[[:space:]]*\// {print $1}'; \
+    done \
+        | sort -u \
+        | xargs -r -I{} cp -L --parents {} /opt/runtime-libs
 
 # Prepare the entrypoint script that will run inside the scratch image
 RUN mkdir -p /opt/config-server \
  && cat <<'EOF' > /opt/config-server/entrypoint.sh
 #!/bin/sh
 set -e
-exec /opt/jre/bin/java -Djava.security.egd=file:/dev/./urandom $JAVA_OPTS -jar /opt/config-server/app.jar
+exec /opt/jre/bin/java -Djava.security.egd=file:/dev/./urandom -Djava.io.tmpdir=/tmp $JAVA_OPTS -jar /opt/config-server/app.jar
 EOF
 RUN chmod +x /opt/config-server/entrypoint.sh
 
@@ -52,6 +59,7 @@ FROM scratch AS runtime
 
 ENV JAVA_HOME=/opt/jre
 ENV JAVA_OPTS=""
+ENV HOME=/home/config
 ENV SERVER_PORT=8888
 ENV SPRING_PROFILES_ACTIVE=git
 ENV CONFIG_GIT_URI=https://github.com/spring-cloud-samples/config-repo
@@ -61,10 +69,18 @@ WORKDIR /opt/config-server
 
 COPY --from=shell /bin/sh /bin/sh
 COPY --from=shell /bin/busybox /bin/busybox
+COPY --from=shell /tmp /tmp
+
+RUN /bin/busybox chown 1001:1001 /tmp \
+ && /bin/busybox chmod 1777 /tmp
+
+RUN /bin/busybox mkdir -p /home/config/.config/jgit \
+ && /bin/busybox chown -R 1001:1001 /home/config
 
 COPY --from=jre-build /etc/passwd /etc/passwd
 COPY --from=jre-build /etc/group /etc/group
 COPY --from=jre-build /opt/jre /opt/jre
+COPY --from=jre-build /opt/runtime-libs/ /
 COPY --from=jre-build /opt/config-server/entrypoint.sh /opt/config-server/entrypoint.sh
 COPY --from=build /workspace/app/target/config-server.jar /opt/config-server/app.jar
 

pom.xml

@@ -26,6 +26,16 @@
         <dependency>
             <groupId>org.springframework.cloud</groupId>
             <artifactId>spring-cloud-config-server</artifactId>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.springframework.boot</groupId>
+                    <artifactId>spring-boot-starter-tomcat</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-jetty</artifactId>
         </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>