# Vert.x Docker Images

Execute Vert.x applications in Docker containers.

## Introduction

Docker lets you deploy applications inside lightweight and isolated software containers. Applications run side by side in isolated Linux containers. If you never used Docker before check this online tutorial.

Vert.x provides Docker images that you can use to run your applications. Two Docker images are provided:

- `vertx/vertx4` is the base image you need to extend to run your own application

- `vertx/vertx4-exec` is providing the `vertx` command to your system without having to install `vert.x` yourself.

The images are available from Docker Hub.

This guide presents how to use these two images but also how to automate Docker image creation using Maven, generate Fabric8 metadata and use fat jars.

## The base image

The base image (`vertx/vertx4`) lets you run your vert.x application in a Docker container. For this, you must extend the image to deploy your own application - i.e. create your own `Dockerfile` inheriting from `vertx/vertx4`. Your application is then launched using the `vertx` command (but in the container).

### Deploying a Groovy verticle in a docker container

Running a groovy verticle in a docker container is not much different. Instead of the `hello-verticle.js` from the previous example, we now have a `hello-verticle.groovy`:

hello-verticle.groovy

    vertx.createHttpServer().requestHandler({ request ->
        request.response().end("Groovy world")
    }).listen(8080)

So, in the `Dockerfile` we just change the verticle file name:

Dockerfile

    # Extend vert.x image
    FROM vertx/vertx4

    # Set the name of the verticle to deploy
    ENV VERTICLE_NAME hello-verticle.groovy

    # Set the location of the verticles
    ENV VERTICLE_HOME /usr/verticles

    EXPOSE 8080

    # Copy your verticle to the container
    COPY $VERTICLE_NAME $VERTICLE_HOME/

    # Launch the verticle
    WORKDIR $VERTICLE_HOME
    ENTRYPOINT ["sh", "-c"]
    CMD ["exec vertx run $VERTICLE_NAME -cp $VERTICLE_HOME/*"]

The build and run instructions are very close to the previous ones:

    > docker build -t sample/vertx-groovy .
    ....
    > docker run -t -i -p 8080:8080 sample/vertx-groovy

### Deploying a Java verticle in a docker container

So, now let’s see how to deploy a Java verticle. Again it’s not different from the previous examples, except that we copy the verticle jar file to the container. Let’s take the following verticle:

io.vertx.sample.hello.HelloVerticle

    package io.vertx.sample.hello;

    import io.vertx.core.AbstractVerticle;

    public class HelloVerticle extends AbstractVerticle {

      @Override
      public void start() throws Exception {
        vertx.createHttpServer().requestHandler(request -> {
          request.response().end("Hello Java world");
        }).listen(8080);
      }
    }

Let’s now imagine that this verticle is packaged into the `target/hello-verticle-1.0.-SNAPSHOT.jar` jar file. So the `Dockerfile` needs to copy this file but also gives to vert.x the verticle class name:

Dockerfile

    # Extend vert.x image
    FROM vertx/vertx4

    #                                                       (1)
    ENV VERTICLE_NAME io.vertx.sample.hello.HelloVerticle
    ENV VERTICLE_FILE target/hello-verticle-1.0-SNAPSHOT.jar

    # Set the location of the verticles
    ENV VERTICLE_HOME /usr/verticles

    EXPOSE 8080

    # Copy your verticle to the container                   (2)
    COPY $VERTICLE_FILE $VERTICLE_HOME/

    # Launch the verticle
    WORKDIR $VERTICLE_HOME
    ENTRYPOINT ["sh", "-c"]
    CMD ["exec vertx run $VERTICLE_NAME -cp $VERTICLE_HOME/*"]

1. Unlike the previous examples, here we set the verticle class name and the jar file

2. The jar file is copied.

Build and run instructions do not change:

    > docker build -t sample/vertx-java .
    ....
    > docker run -t -i -p 8080:8080 sample/vertx-java

### Configuration

The previous `Dockerfile`s did not configure vert.x. Let’s see how such configuration can be added.

#### Configuring the Java Virtual Machine

You can configure the Java Virtual Machine using the `JAVA_OPTS` environment variable. So in the `Dockerfile` adds:

    ENV JAVA_OPTS "-Dfoo=bar"

#### VERTX_OPTS

System variables specific to vert.x can be configured using the `VERTX_OPTS` environment variable:

    ENV VERTX_OPTS "-Dvertx.options.eventLoopPoolSize=26 -Dvertx.options.deployment.worker=true"

#### Classpath

You can configure the classpath of the application using either the `-cp` parameter of the vert.x command or the `CLASSPATH` environment variable:

    ENV CLASSPATH "/usr/verticles/libs/foo.jar:/usr/verticles/libs/bar.jar:"

#### Logging

To configure the `logging.properties` file (that let you customize JUL loggers`), set the `VERTX_JUL_CONFIG` environment variables:

    COPY ./logging.properties $VERTICLE_HOME/                       (1)
    ENV VERTX_JUL_CONFIG $VERTICLE_HOME/logging.properties          (2)

1. Copy your `logging.properties` file

2. Set the `VERTX_JUL_CONFIG` environment variable

#### Clustering

You can provide your own `cluster.xml` file, and add it to the classpath. To build a dynamic classpath from all the file contained in `$VERTICLE_HOME` you can use:

    COPY ./cluster.xml $VERTICLE_HOME/
    # ...
    CMD [export CLASSPATH=`find $VERTICLE_HOME -printf '%p:' | sed 's/:$//'`; exec vertx run $VERTICLE_NAME"]

Notice the `export CLASSPATH=…​;` part in the `CMD` instruction. It builds the value of the `CLASSPATH` variable from the content of the `$VERTICLE_HOME` directory. This tricks is useful to compute large and dynamic classpath.

### Build Docker Images with Maven

There are a couple of Maven plugins to build your Docker images during your Maven build process. This example uses the docker-maven-plugin from Spotify.

First, create your Java project as usual. So your sources are located in `src/main/java`…​ Then create a `src/main/docker` directory and create a `Dockerfile` inside:

    .
    ├── pom.xml
    ├── src
    │   └── main
    │       ├── docker
    │       │   └── Dockerfile
    │       └── java
    │           └── io
    │               └── vertx
    │                   └── example
    │                       └── HelloWorldVerticle.java
    ├── target

In the `pom.xml` file add the following plugin configuration

    <groupId>com.spotify</groupId>
    <artifactId>docker-maven-plugin</artifactId>
    <version>0.2.8</version>
    <executions>
      <execution>
        <id>docker</id>
        <phase>package</phase>
        <goals>
          <goal>build</goal>
        </goals>
      </execution>
    </executions>
    <configuration>
      <dockerDirectory>${project.basedir}/src/main/docker</dockerDirectory>
      <!-- Configure the image name -->
      <imageName>sample/vertx-hello</imageName>
      <resources>
        <resource>
          <targetPath>/verticles</targetPath>
          <directory>${project.build.directory}</directory>
          <includes>
            <include>${project.artifactId}-${project.version}.jar</include>
          </includes>
        </resource>
        <!-- don't forget to also add all the dependencies required by your application -->
      </resources>
    </configuration>
    </plugin>

The plugin copies the listed content into `target/docker`. Each resource is copied into the set `targetPath`. So edit the `src/main/docker/Dockerfile` and add the following content:

    FROM vertx/vertx4

    ENV VERTICLE_HOME /usr/verticles
    ENV VERTICLE_NAME io.vertx.example.HelloWorldVerticle

    COPY ./verticles $VERTICLE_HOME

    ENTRYPOINT ["sh", "-c"]
    CMD ["exec vertx run $VERTICLE_NAME -cp $VERTICLE_HOME/*"]

It’s basically the same content as we saw above. The copy is a bit different as the plugin have placed files in the same directory as the `Dockerfile`.

Once configured the image is built using: `mvn clean package`

### Build Docker Images for Fabric 8

Fabric 8 is an open source set of micro-services that run on top of Kubernetes and OpenShift V3 to provide management, continuous delivery and iPaas facilities. You can execute vert.x application on top of Fabric 8 by packaging them into a Docker image. However, additional metadata is required. In this example, we are going to use the docker-maven-plugin from Roland Huß.

Let’s set up the following structure:

    .
    ├── pom.xml
    ├── src
    │   └── main
    │       ├── docker
    │       │   └── assembly.xml
    │       └── java
    │           └── io
    │               └── vertx
    │                   └── example
    │                       └── HelloWorldVerticle.java
    └── target

Unlike the maven plugin from Spotify, this plugin takes an `assembly.xml` as input. The file lists all the files that need to be copied to the docker container such as:

     <assembly>
       <dependencySets>
         <dependencySet>
           <includes>
             <include>:${project.artifactId}</include>
           </includes>
           <outputDirectory>.</outputDirectory>
         </dependencySet>
       </dependencySets>
     </assembly>

The rest of the `Dockerfile configuration is given in the `pom.xml` file. Add the following plugin to the `pom.xml` file:

     <plugin>
      <groupId>org.jolokia</groupId>
      <artifactId>docker-maven-plugin</artifactId>
      <version>0.11.5</version>
      <executions>
        <execution>
          <id>build</id>
          <phase>package</phase>
          <goals>
            <goal>build</goal>
          </goals>
        </execution>
      </executions>
      <configuration>
        <images>
          <image>
            <name>${docker.image}</name>
            <build>
              <from>vertx/vertx4</from>
              <tags>
                <tag>${project.version}</tag>
              </tags>
              <ports>
                <port>8080</port>
              </ports>
              <command>vertx run io.vertx.example.HelloWorldVerticle -cp
                /usr/verticles/${project.artifactId}-${project.version}.jar
              </command>
              <assembly>
                <mode>dir</mode>
                <basedir>/usr/verticles</basedir>
                <descriptor>assembly.xml</descriptor>
              </assembly>
            </build>
          </image>
        </images>
      </configuration>
     </plugin>

To configure the container more finely, check the manual. All the instructions we put in the `Dockerfile` can be set from the plugin.

Note | The previous `pom.xml` file use a properties called `docker.image` setting the image name. Don’t forget to set it in your pom.xml` file.

Once you have this configuration in place, we need a second plugin to generate the metadata required by Fabric8:

    <plugin>
    <groupId>io.fabric8</groupId>
    <artifactId>fabric8-maven-plugin</artifactId>
    <version>2.1.4</version>
    <executions>
      <execution>
        <id>json</id>
        <phase>generate-resources</phase>
        <goals>
          <goal>json</goal>
        </goals>
      </execution>
      <execution>
        <id>attach</id>
        <phase>package</phase>
        <goals>
          <goal>attach</goal>
        </goals>
      </execution>
    </executions>
    </plugin>

Once set up, you can build your docker image with: `mvn clean package`. It creates the `kubernates.json` file required by Fabric8. Then push your image on the Docker Registry provided by Fabric8:

    docker push $DOCKER_REGISTRY/sample/vertx-hello

Don’t forget to set the `DOCKER_REGISTRY` url to point on the registry managed by Fabric8. The last step is to apply it with:

    mvn io.fabric8:fabric8-maven-plugin:2.1.4:apply

## The executable image

The `vertx/vertx4-exec` image provides the `vertx` command to the host. So no need to install vert.x on your machine, you can just use this docker image.

For instance:

    > docker run -i -t vertx/vertx4-exec -version
    4.3.1

To run a verticle:

    docker run -i -t -p 8080:8080 \
        -v $PWD:/verticles vertx/vertx4-exec \
        run io.vertx.sample.RandomGeneratorVerticle \
        -cp /verticles/MY_VERTICLE.jar

This command mounts the current directory (`PWD`) into `/verticles` and then launch the `vertx run` command. Notice the `-cp` parameter reusing the `/verticles` directory.

### Customizing the stack

The `vertx/vertx4-exec` image provides the default "full" Vert.x stack. You may want to customize this stack and create your own exec image. First, create a `vertx-stack.json` file:

    {
      "variables": {
        "vertx.version": "3.3.3"
      },
      "dependencies": [
        {
          "groupId": "io.vertx",
          "artifactId": "vertx-web",
          "version": "${vertx.version}",
          "included": true
        }
      ]
    }

You can list any dependency you need, not just the Vert.x artifacts (refer to the Stack Manager documentation for details).

Then write a `Dockerfile` for your custom executable image:

    FROM vertx/vertx4-exec                                     (1)

    COPY vertx-stack.json ${VERTX_HOME}/vertx-stack.json       (2)

    RUN vertx resolve && rm -rf ${HOME}/.m2                    (3)

1. Extend the Vert.x executable image

2. Replace the stack file in the Vert.x command installation

3. Resolve dependencies

You should know be able to build your custom executable image:

    docker build -t mycompany/my-vertx4-exec .

And run your verticle:

    docker run -i -t -p 8080:8080 \
        -v $PWD:/verticles mycompany/my-vertx4-exec \
        run io.vertx.sample.RandomGeneratorVerticle \
        -cp /verticles/MY_VERTICLE.jar

## Deploying a fat jar

It is also possible to deploy a Vert.x application packaged as a fat jar into a docker container. For this you don’t need the images provided by Vert.x, you can directly use a base Java image. Let’s have a look.

First, be sure your application is packaged as a fat jar. Then, use the following `Dockerfile`:

    FROM openjdk:8-jre-alpine                                           (1)

    ENV VERTICLE_FILE hello-verticle-fatjar-3.0.0-SNAPSHOT-fat.jar      (2)

    # Set the location of the verticles
    ENV VERTICLE_HOME /usr/verticles

    EXPOSE 8080

    # Copy your fat jar to the container
    COPY target/$VERTICLE_FILE $VERTICLE_HOME/                          (3)

    # Launch the verticle
    WORKDIR $VERTICLE_HOME
    ENTRYPOINT ["sh", "-c"]
    CMD ["exec java -jar $VERTICLE_FILE"]                               (4)

1. Extend the image providing OpenJDK 8, use the one you want

2. Set the `VERTICLE_FILE` to point on the fat jar

3. Copy the Fat jar from target. Change it if you don’t use Maven.

4. Launch the application using the `java` executable (instead of `vertx`

It’s basically the same `Dockerfile` as before. However, this time we extend `java:8` instead of the `vertx/vertx4` image. Then we copy the fat jar to the container, and launch it with the `java` executable. All the configuration settings presented above are still valid.

Build and run the container with:

    > docker build -t sample/vertx-java-fat .
    ....
    > docker run -t -i -p 8080:8080 sample/vertx-java-fat