Java Image Build, Part 2

26 February 2022

Summary: In the previous Blog Post we packaged a single FAT JAR into a container image by utilizing JIB, the Java Image Build tool from Google. With the used Wildfly Bootable JAR some optimizations to the build process are possible. This will be subject to this Blog post.

In part 1 of this mini series about packaging Wildfly bootable JARs with JIB, the build has been performed in a single step. But if we have a closer look at the build steps, we can distinguish

Java build (and unit test execution) of the application
Provisioning of Wildfly application server as bootable JAR
Creating the container image

Typically, during development the application (code) changes frequently, while the provisioned server is more or less stable. Because of that, it would make sense to separate the provisioning of the application server and the build of the application. In this case, the application will be packaged as web application (WAR), while the provisioned server is still an executable JAR file called Hollow JAR - see Blog Post Wildfly Bootable JAR for more details about Hollow JARs.

So, the packaging as Hollow JAR can be beneficial when containerizing applications. Let’s imagine that we create an application server image, that contains only the necessary parts required by our application. Such a image becomes the base image for building the application image itself. That way, the server image containing the Hollow JAR is built once (or at least rarely), while the build of the application takes place frequently, whenever any code changes. Because the application is small compared to the server runtime (just WAR of some kilobytes), the image build is expected to be much faster compared to the previous approach, when server and application has always been re-created from scratch.

Build Setup

For setting up the build, I copied the demo project from the previous Blog Post and separated the packaging of the server runtime and the application itself in two independent Maven projects hosted in two sub-directories.

You’ll find the code of the demo project in JAX/RS Sample Hollow JAR Project.

The project structure of the Hollow JAR project separates the server and app into two distinct and independent Maven projects. The Maven projects are actually independent from Maven’s perspective, i.e. not comprised in a parent (POM) project.

The main differences of the build configuration of the `server`to the build configuration of the first article are

Wildfly JAR plugin creates hollow JAR due to <hollow-jar>true</hollow-jar> configuration
JIB plugin requires additional runtime argument <arg>--deployment=/deployments/ROOT.war/</arg>, because the application’s WAR is built and added later

The packaging of the application build is a regular web application war, so the Wildfly JAR plugin is not required. The JIB plugin configuration look like:

<plugin>
    <groupId>com.google.cloud.tools</groupId>
    <artifactId>jib-maven-plugin</artifactId>
    <version>3.2.0</version>
    <configuration>
        <from>
            <image>docker.io/guntherrotsch/jaxrs-server-jar:jib</image> (1)
        </from>
        <to>
            <!-- to push to external Dockerhub repo -->
            <image>docker.io/guntherrotsch/jaxrs-app:jib</image>
            <auth>
                <username>guntherrotsch</username>
                <password>${docker.password}</password>
            </auth>
        </to>

        <container>
            <entrypoint>INHERIT</entrypoint> (2)
            <appRoot>/deployments/ROOT.war</appRoot> (3)
        </container>
    </configuration>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <!-- to push to external repo -->
                <goal>build</goal>
            </goals>
        </execution>
    </executions>
</plugin>

1	The Hollow JAR `server` image becomes the base image of the application image.
2	The entrypoint of the images is inherited from the base image.
3	The application WAR is added to the `deployments` folder corresponding to the additional runtime argument of the `server` build.

Image Build and Execution

With the Maven configuration in place the images, server as well as application, can be build:

[jaxrs-hollow-jar] cd server
[jaxrs-hollow-jar/server] mvn verify jib:build -DDOCKERHUB_TOKEN=${DOCKERHUB_TOKEN}
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< net.gunther.wildfly:jaxrs-server >------------------
[INFO] Building jaxrs-server 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]

...

[INFO] --- wildfly-jar-maven-plugin:7.0.0.Final:package (default) @ jaxrs-server ---
[INFO] Provisioning server configuration based on the set of configured layers
[INFO] Building server based on [[wildfly@maven(org.jboss.universe:community-universe)#26.0.1.Final inherit-packages=false inheritConfigs=false]] galleon feature-packs
[INFO] Found boot artifact org.wildfly.core:wildfly-jar-boot:jar:18.0.4.Final:provided in org.wildfly:wildfly-ee-galleon-pack:26.0.1.Final
[INFO] CLI executions are done in forked process
[INFO] Hollow jar, No application deployment added to server.
[INFO] Executing CLI, CLI Session, scripts=[scripts/logging.cli], resolve-expressions=true, properties-file=scripts/cli.properties
[INFO] CLI scripts execution done.
[INFO]
[INFO] --- jib-maven-plugin:3.2.0:build (default) @ jaxrs-server ---
[INFO]
[INFO] Containerizing application to guntherrotsch/jaxrs-server-jar:jib...
[WARNING] Base image 'gcr.io/distroless/java:11' does not use a specific image digest - build may not be reproducible
[INFO] Using credentials from <to><auth> for guntherrotsch/jaxrs-server-jar:jib
[INFO] Using base image with digest: sha256:b45698486fb932b6a1b462b86a0038f0b53df905575c91c8b591974f3e0cac98
[INFO]
[INFO] Container entrypoint set to [java, -cp, /app/classpath/*:/app/libs/*, org.wildfly.core.jar.boot.Main]
[INFO] Container program arguments set to [-b=0.0.0.0, --deployment=/deployments/ROOT.war/]
[INFO]
[INFO] Built and pushed image as guntherrotsch/jaxrs-server-jar:jib
[INFO] Executing tasks:
[INFO] [============================  ] 91.7% complete
[INFO] > launching layer pushers
[INFO]
[INFO]
[INFO] --- jib-maven-plugin:3.2.0:build (default-cli) @ jaxrs-server ---
[INFO]
[INFO] Containerizing application to guntherrotsch/jaxrs-server-jar:jib...
[WARNING] Base image 'gcr.io/distroless/java:11' does not use a specific image digest - build may not be reproducible
[INFO] Using credentials from <to><auth> for guntherrotsch/jaxrs-server-jar:jib
[INFO] Using base image with digest: sha256:b45698486fb932b6a1b462b86a0038f0b53df905575c91c8b591974f3e0cac98
[INFO]
[INFO] Container entrypoint set to [java, -cp, /app/classpath/*:/app/libs/*, org.wildfly.core.jar.boot.Main]
[INFO] Container program arguments set to [-b=0.0.0.0, --deployment=/deployments/ROOT.war/]
[INFO]
[INFO] Built and pushed image as guntherrotsch/jaxrs-server-jar:jib
[INFO] Executing tasks:
[INFO] [============================  ] 91.7% complete
[INFO] > launching layer pushers
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  46.806 s
[INFO] Finished at: 2022-02-16T11:34:32+01:00
[INFO] ------------------------------------------------------------------------
[jaxrs-hollow-jar/server]
[jaxrs-hollow-jar/server] $ podman pull docker.io/guntherrotsch/jaxrs-server-jar:jib
Trying to pull docker.io/guntherrotsch/jaxrs-server-jar:jib...
Getting image source signatures
Copying blob c6f4d1a13b69 skipped: already exists
Copying blob a1f1879bb7de skipped: already exists
Copying blob 2df365faf0e3 skipped: already exists
Copying blob 7f693fb4c128 done
Copying blob 86e52a123483 done
Copying blob f8637ebdb9cf done
Copying blob dc592bd45c36 done
Copying config 7f1a44fa17 done
Writing manifest to image destination
Storing signatures
7f1a44fa17caf6e8c75b9005c0903ccaec5d7274683714ebea21403451ebfcb1

[jaxrs-hollow-jar/server] cd ../app
[jaxrs-hollow-jar/app]

[jaxrs-hollow-jar/app]

[jaxrs-hollow-jar/app]

[jaxrs-hollow-jar/app] mvn verify jib:build -DDOCKERHUB_TOKEN=${DOCKERHUB_TOKEN}
[INFO] Scanning for projects...
Downloading from central: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-war-plugin/3.1.0/maven-war-plugin-3.1.0.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-war-plugin/3.1.0/maven-war-plugin-3.1.0.pom (9.3 kB at 16 kB/s)
Downloading from central: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-war-plugin/3.1.0/maven-war-plugin-3.1.0.jar
Downloaded from central: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-war-plugin/3.1.0/maven-war-plugin-3.1.0.jar (91 kB at 666 kB/s)
[INFO]
[INFO] -------------------< net.gunther.wildfly:jaxrs-app >--------------------
[INFO] Building jaxrs-app 1.0-SNAPSHOT
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ jaxrs-app ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /home/gunther/_work/repos/GuntherRotsch.github.com/guntherrotsch.github.io/code/jaxrs-hollow-jar/app/src/main/resources

...

[INFO]
[INFO] --- maven-war-plugin:3.1.0:war (default-war) @ jaxrs-app ---
[INFO] Packaging webapp
[INFO] Assembling webapp [jaxrs-app] in [/home/gunther/_work/repos/GuntherRotsch.github.com/guntherrotsch.github.io/code/jaxrs-hollow-jar/app/target/jaxrs-app]
[INFO] Processing war project
[INFO] Webapp assembled in [25 msecs]
[INFO] Building war: /home/gunther/_work/repos/GuntherRotsch.github.com/guntherrotsch.github.io/code/jaxrs-hollow-jar/app/target/jaxrs-app.war
[INFO]
[INFO] --- jib-maven-plugin:3.2.0:build (default) @ jaxrs-app ---
[INFO]
[INFO] Containerizing application to guntherrotsch/jaxrs-app:jib...
[WARNING] Base image 'guntherrotsch/jaxrs-server-jar:jib' does not use a specific image digest - build may not be reproducible
[INFO] Using credentials from <to><auth> for guntherrotsch/jaxrs-app:jib
[INFO] The base image requires auth. Trying again for guntherrotsch/jaxrs-server-jar:jib...
[INFO] Using credentials from Docker config (/home/gunther/.docker/config.json) for guntherrotsch/jaxrs-server-jar:jib
[INFO] Using base image with digest: sha256:d038a8f169944753f157b644c135dbb54ab645d71112cb5da7f16bd85955d39e
[INFO]
[INFO] Container entrypoint set to [java, -cp, /app/classpath/*:/app/libs/*, org.wildfly.core.jar.boot.Main] (inherited from base image)
[INFO] Container program arguments set to [-b=0.0.0.0, --deployment=/deployments/ROOT.war/] (inherited from base image)
[INFO]
[INFO] Built and pushed image as guntherrotsch/jaxrs-app:jib
[INFO] Executing tasks:
[INFO] [============================  ] 92.9% complete
[INFO] > launching layer pushers
[INFO]
[INFO]
[INFO] --- jib-maven-plugin:3.2.0:build (default-cli) @ jaxrs-app ---
[INFO]
[INFO] Containerizing application to guntherrotsch/jaxrs-app:jib...
[WARNING] Base image 'guntherrotsch/jaxrs-server-jar:jib' does not use a specific image digest - build may not be reproducible
[INFO] Using credentials from <to><auth> for guntherrotsch/jaxrs-app:jib
[INFO] The base image requires auth. Trying again for guntherrotsch/jaxrs-server-jar:jib...
[INFO] Using credentials from Docker config (/home/gunther/.docker/config.json) for guntherrotsch/jaxrs-server-jar:jib
[INFO] Using base image with digest: sha256:d038a8f169944753f157b644c135dbb54ab645d71112cb5da7f16bd85955d39e
[INFO]
[INFO] Container entrypoint set to [java, -cp, /app/classpath/*:/app/libs/*, org.wildfly.core.jar.boot.Main] (inherited from base image)
[INFO] Container program arguments set to [-b=0.0.0.0, --deployment=/deployments/ROOT.war/] (inherited from base image)
[INFO]
[INFO] Built and pushed image as guntherrotsch/jaxrs-app:jib
[INFO] Executing tasks:
[INFO] [============================  ] 91.7% complete
[INFO] > launching layer pushers
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  24.552 s
[INFO] Finished at: 2022-02-16T11:42:50+01:00
[INFO] ------------------------------------------------------------------------

[jaxrs-hollow-jar/app] podman pull docker.io/guntherrotsch/jaxrs-app:jib
Trying to pull docker.io/guntherrotsch/jaxrs-app:jib...
Getting image source signatures
Copying blob 86e52a123483 skipped: already exists
Copying blob c6f4d1a13b69 skipped: already exists
Copying blob f8637ebdb9cf skipped: already exists
Copying blob dc592bd45c36 skipped: already exists
Copying blob a1f1879bb7de skipped: already exists
Copying blob 2df365faf0e3 skipped: already exists
Copying blob 7f693fb4c128 skipped: already exists
Copying blob aa8ec6fe4535 done
Copying blob f0e3c6c4292c done
Copying config 519f539e98 done
Writing manifest to image destination
Storing signatures
519f539e98d032fc1b986f8cb907b1f6e35408d8d5c18f22eb1b0398bb34ec77

Because the application image is based on the server image, the build requires only half of the time about. Please note the many already existing layers reported by the build log.

Now we can execute the application and test it:

[jaxrs-hollow-jar] podman images
REPOSITORY                                TAG        IMAGE ID      CREATED       SIZE
docker.io/guntherrotsch/jaxrs-jar         jib        07440e12af76  52 years ago  276 MB
docker.io/guntherrotsch/jaxrs-jar         jib-debug  ad70cdb363dd  52 years ago  505 MB
docker.io/guntherrotsch/jaxrs-server-jar  jib        7f1a44fa17ca  52 years ago  277 MB
docker.io/guntherrotsch/jaxrs-app         jib        519f539e98d0  52 years ago  277 MB

[jaxrs-hollow-jar] $ podman run --rm -it --publish "0.0.0.0:8080:8080" docker.io/guntherrotsch/jaxrs-app:jib
10:46:08,328 INFO  [org.wildfly.jar] (main) WFLYJAR0006: Deployed /deployments/ROOT.war in server
10:46:08,338 INFO  [org.wildfly.jar] (main) WFLYJAR0007: Installed server and application in /tmp/wildfly-bootable-server935367089119766930, took 1144ms
10:46:08,621 INFO  [org.wildfly.jar] (main) WFLYJAR0008: Server options: [-b=0.0.0.0, --read-only-server-config=standalone.xml]
10:46:08,718 INFO  [org.jboss.msc] (main) JBoss MSC version 1.4.13.Final
10:46:08,724 INFO  [org.jboss.threads] (main) JBoss Threads version 2.4.0.Final
10:46:08,865 INFO  [org.jboss.as] (MSC service thread 1-3) WFLYSRV0049: WildFly Full 26.0.1.Final (WildFly Core 18.0.4.Final) starting

...

10:46:10,120 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-4) WFLYUT0003: Undertow 2.2.14.Final starting
10:46:10,215 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-2) WFLYUT0012: Started server default-server.
10:46:10,216 WARN  [org.wildfly.extension.elytron] (MSC service thread 1-5) WFLYELY00023: KeyStore file '/tmp/wildfly-bootable-server935367089119766930/standalone/configuration/application.keystore' does not exist. Used blank.
10:46:10,222 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-6) Queuing requests.
10:46:10,223 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-6) WFLYUT0018: Host default-host starting
10:46:10,235 WARN  [org.wildfly.extension.elytron] (MSC service thread 1-2) WFLYELY01084: KeyStore /tmp/wildfly-bootable-server935367089119766930/standalone/configuration/application.keystore not found, it will be auto generated on first use with a self-signed certificate for host localhost
10:46:10,283 WARN  [org.jboss.as.domain.http.api.undertow] (MSC service thread 1-4) WFLYDMHTTP0003: Unable to load console module for slot main, disabling console
10:46:10,319 INFO  [org.jboss.as.server.deployment] (MSC service thread 1-2) WFLYSRV0027: Starting deployment of "ROOT.war" (runtime-name: "ROOT.war")
10:46:10,328 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-8) WFLYUT0006: Undertow HTTP listener default listening on [0:0:0:0:0:0:0:0]:8080
10:46:11,802 INFO  [org.jboss.resteasy.resteasy_jaxrs.i18n] (ServerService Thread Pool -- 23) RESTEASY002225: Deploying javax.ws.rs.core.Application: class net.gunther.wildfly.demo.app.RestApplication
10:46:11,902 INFO  [org.hibernate.validator.internal.util.Version] (ServerService Thread Pool -- 23) HV000001: Hibernate Validator 6.0.22.Final
10:46:12,012 INFO  [org.wildfly.extension.undertow] (ServerService Thread Pool -- 23) WFLYUT0021: Registered web context: '/' for server 'default-server'
10:46:12,015 INFO  [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0010: Deployed "ROOT.war" (runtime-name : "ROOT.war")
10:46:12,051 INFO  [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0212: Resuming server
10:46:12,055 INFO  [org.jboss.as] (Controller Boot Thread) WFLYSRV0025: WildFly Full 26.0.1.Final (WildFly Core 18.0.4.Final) started in 3428ms - Started 160 of 166 services (33 services are lazy, passive or on-demand)
10:46:12,057 INFO  [org.jboss.as] (Controller Boot Thread) WFLYSRV0060: Http management interface listening on http://127.0.0.1:9990/management
10:46:12,057 INFO  [org.jboss.as] (Controller Boot Thread) WFLYSRV0054: Admin console is not enabled

In a different terminal cURL can be used to request the hello end-point:

$ curl localhost:8080/hello
Hello from Wildfly JAR

Looks like everything works fine, really cool.

Conclusion

As we already noticed in the first article, JIB tooling provides an easy and straight-forward way to build containerized Java applications without leaving the Java development environment. With the optimization for Wildfly Bootable JAR projects presented here, we in addition get a really fast image build, which safes a lot of time in Edit-Build-Test cycles.

Links

Tags: cloud-native docker wildfly maven java jib container