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User Manual

The following sections describe the installation of this plugin, the available goals and its configuration options.

Installation

This plugin is available from Maven central and can be connected to pre- and post-integration phase as seen below. The configuration and available goals are described below.

<plugin>
  <groupId>org.jolokia</groupId>
  <artifactId>docker-maven-plugin</artifactId>
  <version>0.10.5</version>

  <configuration>
     ....
     <images>
        <!-- A single's image configuration -->
        <image>
           ....
        </image>
        ....
     </images>
  </configuration>

  <!-- Connect start/stop to pre- and
       post-integration-test phase, respectively if you want to start
       your docker containers during integration tests -->
  <executions>
    <execution>
       <id>start</id>
       <phase>pre-integration-test</phase>
       <goals>
         <!-- "build" should be used to create the images with the
              artefacts --> 
         <goal>build</goal>
         <goal>start</goal>
       </goals>
    </execution>
    <execution>
       <id>stop</id>
       <phase>post-integration-test</phase>
       <goals>
         <goal>stop</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Global configuration

Global configuration parameters specify overall behavior like the connection to the Docker host. The corresponding system properties which can be used to set it from the outside are given in parentheses.

  • dockerHost (docker.host) Use this variable to specify the URL to on your Docker Daemon is listening. This plugin requires the usage of the Docker remote API so this must be enabled. If this configuration option is not given, the environment variable DOCKER_HOST is evaluated. If this is also not set the plugin will stop with an error. The scheme of this URL can be either given directly as http or https depending on whether plain HTTP communication is enabled (< 1.3.0) or SSL should be used (>= 1.3.0). Or the scheme could be tcp in which case the protocol is determined via the IANA assigned port: 2375 for http and 2376 for https.
  • apiVersion (docker.apiVersion) Use this variable if you are using an older version of docker not compatible with the current default use to communicate with the server.
  • certPath (docker.certPath) Since 1.3.0 Docker remote API requires communication via SSL and authentication with certificates when used with boot2docker. These certificates are normally stored in ~/.docker/. With this configuration the path can be set explicitly. If not set, the fallback is first taken from the environment variable DOCKER_CERT_PATH and then as last resort ~/.docker/. The keys in this are expected with it standard names ca.pem, cert.pem and key.pem. Please refer to the Docker documentation for more information about SSL security with Docker.
  • image (docker.image) In order to temporarily restrict the operation of plugin goals this configuration option can be used. Typically this will be set via the system property docker.image when Maven is called. The value can be a single image name (either its alias or full name) or it can be a comma separated list with multiple image names. Any name which doesn't refer an image in the configuration will be ignored.
  • useColor (docker.useColor) If set to true the log output of this plugin will be colored. By default the output is colored if the build is running with a TTY, without color otherwise.
  • skip (docker.skip) With this parameter the execution of this plugin can be skipped completely.
  • registry (docker.registry) Specify globally a registry to use for pulling and pushing images. See Registry handling for details.
  • autoPull (docker.autoPull) By default external images (base image for building or images to start) are downloaded automatically. With this options this can be switched off by setting this value to false.
  • authConfig holds the authentication information when pulling from or pushing to Docker registry. There is a dedicated section for how doing security.
  • logDate (docker.logDate) specifies the date format which is used for printing out container logs. This configuration can be overwritten by individual run configurations and described below. The format is described in the section below.
  • sourceDirectory (docker.source.dir) specifies the default directory that contains the assembly descriptor(s) used by the plugin. The default value is src/main/docker. This option is only relevant for the docker:build goal.
  • outputDirectory (docker.target.dir) specifies the default output directory to be used by the plugin. The default value is target/docker and is only used for the goal docker:build.

Example:

<configuration>
   <dockerHost>https://localhost:2376</dockerHost>
   <certPath>src/main/dockerCerts</certPath>
   <useColor>true</userColor>
   .....
</configuration>

Image configuration

The plugin's configuration is centered around images. These are lockspecified for each image within the <images> element of the configuration with one <image> element per image to use.

The <image> element can contain the following sub elements:

  • name : Each <image> configuration has a mandatory, unique docker repository name. This can include registry and tag parts, too. For definition of the repository name please refer to the Docker documentation
  • alias is a shortcut name for an image which can be used for identifying the image within this configuration. This is used when linking images together or for specifying it with the global image configuration.
  • registry is a registry to use for this image. If the name already contains a registry this takes precedence. See Registry handling for more details.
  • build is a complex element which contains all the configuration aspects when doing a docker:build or docker:push. This element can be omitted if the image is only pulled from a registry e.g. as support for integration tests like database images.
  • run contains subelements which describe how containers should be created and run when docker:start or docker:stop is called. If this image is only used a data container for exporting artifacts via volumes this section can be missing.
  • external can be used to fetch the configuration through other means than the intrinsic configuration with run and build. It contains a <type> element specifying the handler for getting the configuration. See External configuration for details.

Either <build> or <run> must be present. They are explained in details in the corresponding goal sections.

Example:

<configuration>
  ....
  <images>
    <image>
      <name>jolokia/docker-demo:0.1</name>
      <alias>service</alias>
      <run>....</run>
      <build>....</build>      
    </image>  
  </images>
</configuration>

Maven Goals

This plugin supports the following goals which are explained in detail in the following sections.

Goal Description
docker:build Build images
docker:start Create and start containers
docker:stop Stop and destroy containers
docker:push Push images to a registry
docker:remove Remove images from local docker host
docker:logs Show container logs

Note that all goals are orthogonal to each other. For example in order to start a container for your application you typically have to build its image before. docker:start does not imply building the image so you should use it then in combination with docker:build.

docker:build

This goal will build all images which have a <build> configuration section, or, if the global configuration image is set, only those images contained in this variable will be build.

All build relevant configuration is contained in the <build> section of an image configuration. The available subelements are

  • assembly specifies the assembly configuration as described in Build Assembly
  • command is the command to execute by default (i.e. if no command is provided when a container for this image is started).
  • env hold environments as described in Setting Environment Variables.
  • from specifies the base image which should be used for this image. If not given this default to busybox:latest and is suitable for a pure data image.
  • ports describes the exports ports. It contains a list of <port> elements, one for each port to expose.
  • volumes contains a list of volume elements to create a container volume.
  • tags contains a list of additional tag elements with which an image is to be tagged after the build.

From this configuration this Plugin creates an in-memory Dockerfile, copies over the assembled files and calls the Docker daemon via its remote API. In a future version you will be able to specify alternatively an own Dockerfile (possibly containing maven properties) for better customization.

Here's an example:

<build>
  <from>java:8u40</from>
  <tags>
    <tag>latest</tag>
    <tag>${project.version}</tag>
  </tags>
  <ports>
    <port>8080</port>
  </ports>
  <volumes>
    <volume>/path/to/expose</volume>
  </volumes>
  <command>java /opt/demo/server.jar</command>
  <assembly>
    <basedir>/opt/demo</basedir>
    <descriptor>assembly.xml</descriptor>
  </assembly>
</build>
Build Assembly
  • basedir depicts the directory under which the files and artifacts contained in the assembly will be copied within the container. The default value for this is /maven.
  • descriptor is a reference to an assembly descriptor as described in the section Docker Assembly below.
  • descriptorRef is an alias to a predefined assembly descriptor. The available aliases are also described in the Docker Assembly section.
  • dockerFileDir specifies a directory containing an external Dockerfile that will be used to create the image. Any additional files located in this directory will also be added to the image. Usage of this directive will take precedence over any configuration specified in the build element. In addition to the files specified within the assembly also all files contained in this directory are added to the docker build directory.
  • exportBasedir indicates if the basedir should be exported as a volume. This value is true by default except in the case the basedir is set to the container root (/), which cannot be exported.
  • ignorePermissions indicates if existing file permissions should be ignored when creating the assembly archive. This value is false by default.

In the event you do not need to include any artifacts with the image, you may safely omit this element from the configuration.

Docker Assembly

With using the descriptor or descriptorRef option it is possible to bring local files, artifacts and dependencies into the running Docker container. A descriptor points to a file describing the data to put into an image to build. It has the same format as for creating assemblies with the maven-assembly-plugin with following exceptions:

  • <formats> are ignored, the assembly will allways use a directory when preparing the data container (i.e. the format is fixed to dir)
  • The <id> is ignored since only a single assembly descriptor is used (no need to distinguish multiple descriptors)

Alternatively descriptorRef can be used with the name of a predefined assembly descriptor. The following symbolic names can be used for assemblyDescriptorRef:

  • artifact-with-dependencies will copy your project's artifact and all its dependencies
  • artifact will copy only the project's artifact but no dependencies.
  • project will copy over the whole Maven project but with out target/ directory.
  • rootWar will copy the artifact as ROOT.war to the exposed directory. I.e. Tomcat will then deploy the war under the root context.

All declared files end up in the configured basedir (or /maven by default) in the created image.

In the following example a dependency from the pom.xml is included and mapped to the name jolokia.war. With this configuration you will end up with an image, based on busybox which has a directory /maven containing a single file jolokia.war. This volume is also exported automatically.

<assembly>
  <dependencySets>
    <dependencySet>
      <includes>
        <include>org.jolokia:jolokia-war</include>
      </includes>
      <outputDirectory>.</outputDirectory>
      <outputFileNameMapping>jolokia.war</outputFileNameMapping>
    </dependencySet>
  </dependencySets>
</assembly>

Another container can now connect to the volume an 'mount' the /maven directory. A container from consol/tomcat-7.0 will look into /maven and copy over everything to /opt/tomcat/webapps before starting Tomcat.

If you are using the artifact or artifact-with-dependencies descriptor, it is possible to change the name of the final build artifact with the following:

<build>
  <finalName>your-desired-final-name</build>
  ...
</build>

Please note, based upon the following documentation listed here, there is no guarantee the plugin creating your artifact will honor it in which case you will need to use a custom descriptor like above to achieve the desired naming.

At the time of this writing, the jar and war plugins properly honor the usage of finalName.

docker:start

Creates and starts docker containers. This goals evaluates the configuration's <run> section of all given (and enabled images)

The <run> configuration knows the following sub elements:

  • volumes for bind configurtion of host directories and from other containers. See "[Volume binding]" (#volume-binding) for details.
  • capAdd (v1.14) a list of add elements to specify kernel parameters to add to the container.
  • capDrop (v1.14) a list of drop elements to specify kernel parameters to remove from the container.
  • command is a command which should be executed at the end of the container's startup. If not given, the image's default command is used.
  • domainname (v1.12) domain name for the container
  • dns (v1.11) list of host elements specifying dns servers for the container to use
  • dnsSearch (v1.15) list of host elements specying dns search domains
  • entrypoint (v1.15) set the entry point for the container
  • env can contain environment variables as subelements which are set during startup of the container. The are specified in the typical maven property format as described below.
  • extraHosts (v1.15) list of host elements in the form host:ip to add to the container's /etc/hosts file.
  • hostname (v1.11) desired hostname for the container
  • links declares how containers are linked together see description on container linking.
  • log specifies the log configuration for whether and how log messages from the running containers should be printed. See below for a detailed description of this configuration section.
  • memory (v1.11) memory limit in bytes
  • memorySwap (v1.11) total memory usage (memory + swap); use -1 to disable swap.
  • portPropertyFile, if given, specifies a file into which the mapped properties should be written to. The format of this file and its purpose are also described below
  • ports declares how container exposed ports should be mapped. This is described below in an extra section.
  • privileged (v1.11) give container full access to host (true|false)
  • restartPolicy (v1.15) specifies the container restart policy, see below
  • showLogs allows, if set, to see all standard output and standard error messages for all containers selected. As value the images for which logs should be shown can be given as a comma separated list. This is probably most useful when used from the command line as system property docker.showLogs.
  • user (v1.11) user used inside the container
  • wait specifies condition which must be fulfilled for the startup to complete. See below which subelements are available and how they can be specified.
  • workingDir (v1.11) working dir for commands to run in

Example:

<run>
  <env>
    <CATALINA_OPTS>-Xmx32m</CATALINA_OPTS>
    <JOLOKIA_OFF/>
  </env>
  <ports>
    <port>jolokia.port:8080</port>
  </ports>
  <links>
    <link>db</db>
  </links>
  <wait>
    <url>http://localhost:${jolokia.port}/jolokia</url>
    <time>10000</time>
  </wait>
  <log>
    <prefix>DEMO</prefix>
    <date>ISO8601</date>
    <color>blue</color>
  </log>
  <command>java -jar /maven/docker-demo.jar</command>
</run>
Setting environment variables

When creating a container one or more environment variables can be set via configuration with the env parameter

<env>
  <JAVA_HOME>/opt/jdk8</JAVA_HOME>
  <CATALINA_OPTS>-Djava.security.egd=file:/dev/./urandom</CATALINA_OPTS>
</env>

If you put this configuration into profiles you can easily create various test variants with a single image (e.g. by switching the JDK or whatever).

Port Mapping

The <ports> configuration contains a list of port mappings. Each mapping has multiple parts, each separate by a colon. This is equivalent to the port mapping when using the Docker CLI with option -p.

<ports>
  <port>18080:8080</port> 
  <port>host.port:80</port> 
<ports>

A port stanza may take one of two forms:

  • A tuple consisting of two numeric values separated by a :. This form will result in an explicit mapping between the docker host and the corresponding port inside the container. In the above example, port 18080 would be exposed on the docker host and mapped to port 8080 in the running container.
  • A tuple consisting of a string and a numeric value separated by a :. In this form, the string portion of the tuple will correspond to a Maven property. If the property is undefined when the start task executes, a port will be dynamically selected by Docker in the range 49000 ... 49900 and assigned to the property which may then be used later in the same POM file. If the property exists and has a numeric value, that value will be used as the exposed port on the docker host as in the previous form. In the above example, the docker service will elect a new port and assign the value to the property host.port which may then later be used in a property expression similar to <value>${host.port}</value>. This can be used to pin a port from the outside when doing some initial testing similar to mvn -Dhost.port=10080 docker:start

Both forms of the port stanza also support binding to a specific ip address on the docker host.

<ports>
  <port>1.2.3.4:80:80</port>
  <port>1.2.3.4:host.port:80</port>
</ports>

As a convenience, a hostname pointing to the docker host may also be specified. The container will fail to start if the hostname resolves to an ip address of something other then the docker host itself.

<ports>
  <port>docker.example.com:80:80</port>
</ports>

Another useful configuration option is portPropertyFile with which a file can be specified to which the real port mapping is written after all dynamic ports has been resolved. The keys of this property file are the variable names, the values are the dynamically assigned host ports. This property file might be useful together with other maven plugins which already resolved their maven variables earlier in the lifecycle than this plugin so that the port variables might not be available to them.

Container linking

The <links> configuration contains a list of containers that should be linked to this container according to Docker Links. Each link can have two parts where the optional right side is separated by a : and will be used as the name in the environment variables and the left side refers to the name of the container linking to. This is equivalent to the linking when using the Docker CLI --link option.

Example for linking to a container with name or alias postgres :

<links>
  <link>postgres:db</link>
</links>

This will create the following environment variables, given that the postgres image exposes TCP port 5432:

DB_NAME=/web2/db
DB_PORT=tcp://172.17.0.5:5432
DB_PORT_5432_TCP=tcp://172.17.0.5:5432
DB_PORT_5432_TCP_PROTO=tcp
DB_PORT_5432_TCP_PORT=5432
DB_PORT_5432_TCP_ADDR=172.17.0.5
Volume binding

A container can bind (or "mount") volumes from various source when starting up: Either from a directory of the host system or from another container which exports one or more directories. The mount configuration is specified within a <volumes> section of the run configuration. It can contain the following sub elements:

  • from can contain a list of <image> elements which specify image names or aliases of containers whose volumes should be imported.
  • bind can contain a list of <volume> specifications (or 'host mounts). Use /path to create and expose a new volume in the containaer, /host_path:/container_path to mount a host path into the container and /host_path:/container_path:ro to bind it read-only.
<volumes>
  <bind>
    <volume>/logs</volume>
    <volume>/opt/host_export:/opt/container_import</volume>
  </bind>
  <from>
    <image>jolokia/docker-demo</image>
  </from>
</volumes>

In this example the container mounts from the host /logs as /logs on the container, and /opt/host_export from the host as /opt/container_import on the container. In addition all exported volumes from the container which has been created from the image jolokia/docker-demo are mounted directly into the container (with the same name as the exporting container exposes these directories). The image must be also configured for this plugin. Instead of the full image name, an alias name like service can be used, too.

Container restart policy

Specify the behavior to apply when the container exits. These values can be specified withing a <restartPolicy> section with the following sub-elements:

  • name restart policy name, choose from: -- always (v1.15) always restart -- on-failure (v1.15) restart on container non-exit code of zero
  • retry if on-failure is used, controls max number of attempts to restart before giving up.

The behavior to apply when the container exits. The value is an object with a Name property of either "always" to always restart or "on-failure" to restart only when the container exit code is non-zero. If on-failure is used, MaximumRetryCount controls the number of times to retry before giving up. The default is not to restart. (optional)

Wait during startup and shutdown

While starting a container is it possible to block the execution until some condition is met. These conditions can be specified within a <wait> section which the following sub-elements:

  • url is an URL which is polled periodically until it returns a HTTP 200 status code.
  • log is a regular expression which is applied against the log output of an container and blocks until the pattern is matched.
  • time is the time in milliseconds to block.
  • shutdown is the time to wait in milliseconds between stopping a container and removing it. This might be helpful in situation where a Docker croaks with an error when trying to remove a container to fast after it has been stopped.

As soon as one condition is met the build continues. If you add a <time> constraint this works more or less as a timeout for other conditions.

Example:

<wait>
  <url>http://localhost:${host.port}</url>
  <time>10000</time>
  <shutdown>500</shutdown>
</wait>

This setup will wait for the given URL to be reachable but ten seconds at most. Also, when stopping the container after an integration tests, the build wait for 500 ms before it tries to remove the container (if not keepContainer or keepRunning is used). You can use maven properties in each condition, too. In the example, the ${host.port} property is probably set before within a port mapping section.

Log configuration

When running containers the standard output and standard error of the container can be printed out. Several options are available for configuring the log output:

  • enabled If given and set to false log output is disabled. This is useful if you want to disable log output by default but want to use the other configuration options when log output is switched on on the command line with -Ddocker.showLogs. Logging is enabled by default if a <log> section is given.
  • prefix Prefix to use for the log output in order to identify the container. By default the image alias is used or alternatively the container id.
  • date Dateformat to use for log timestamps. If <date> is not given no timestamp will be shown. The date specification can be either a constant or a date format. The recognized constants are:
    • NONE Switch off timestamp output. Useful on the command line (-Ddocker.logDate=NONE) for switching off otherwise enabled logging.
    • DEFAULT A default format in the form HH:mm:ss.SSS
    • MEDIUM Joda medium date time format
    • SHORT Joda short date time format
    • LONG Joda long date time format
    • ISO8601 Full ISO-8601 formatted date time with milli seconds As an alternative a date-time format string as recognized by JodaTime is possible. In order to set a consistent date format the global configuration parameter logDate can be used.
  • color Color used for coloring the prefix when coloring is enabeld (i.e. if running in a console and useColor is set). The available colors are YELLOW, CYAN, MAGENTA, GREEN, RED, BLUE. If coloring is enabled and now color is provided a color is picked for you.

Example (values can be case insensitive, too) :

<log>
  <prefix>TC</prefix>
  <date>default</date>
  <color>cyan</color>
</log>

docker:stop

Stops and removes a docker container. This goals starts every container started with <docker:stop> either during the same build (e.g. when bound to lifecycle phases when doing integration tests) or for containers created by a previous call to <docker:start>

If called within the same build run it will exactly stop and destroy all containers started by this plugin. If called in a separate run it will stop (and destroy) all containers which were created from images which are configured for this goal. This might be dangerous, but of course you can always stop your containers with the Docker CLI, too.

For tuning what should happen when stopping there are two global parameters which are typically used as system properties:

  • keepContainer (docker.keepContainer) If given will not destroy container after they have been stopped.
  • keepRunning (docker.keepRunning) actually won't stop the container. This apparently makes only sense when used on the command line when doing integration testing (i.e. calling docker:stop during a lifecycle binding) so that the container are still running after an integration test. This is useful for analysis of the containers (e.g. by entering it with docker exec).

Example:

$ mvn -Ddocker.keepRunning clean install

docker:push

This goals uploads images to the registry which have a <build> configuration section. The images to push can be restricted with with the global option image (see Global Configuration for details). The registry to push is by default registry.hub.docker.io but can be specified as part of the images's name name the Docker way. E.g. docker.test.org:5000/data:1.5 will push the image data with tag 1.5 to the registry docker.test.org at port 5000. Security information (i.e. user and password) can be specified in multiple ways as described in an extra section.

docker:remove

This goal can be used to clean up images and containers. By default all so called data images are removed with its containers. A data image is an image without a run configuration. This can be tuned by providing the properties removeAll which indicates to remove all images managed by this build. As with the other goals, the configuration image can be used to tune the images to remove. All containers belonging to the images are removed as well.

Considering three images 'db','tomcat' and 'data' where 'data' is the only data images this example demonstrates the effect of this goal:

  • mvn docker:remove will remove 'data'
  • mvn -Ddocker.removeAll docker:remove will remove all three images
  • mvn -Ddocker.image=data,tomcat docker:remove will remove 'data'
  • mvn -Ddocker.image=data,tomcat -Ddocker.removeAll docker:remove will remove 'data' and 'tomcat'

docker:logs

With this goal it is possible to print out the logs of containers started from images configured in this plugin. By default only the latest container started is printed, but this can be changed with a property. The format of the log output is influenced by run configuration of the configured images. The following system properties can the behaviour of this goal:

  • docker.logAll if set to true the logs of all containers created from images configured for this plugin are printed. The container id is then prefixed before every log line. These images can contain many containers which are already stopped. It is probably a better idea to use docker logs diretly from the command line.
  • docker.follow if given will wait for subsequent log output until CRTL-C is pressed. This is similar to the behaviour of docker logs -f (or tail -f).
  • docker.image can be used to restrict the set of images for which log should be fetched. This can be a comma separated list of image or alias names.
  • docker.logDate specifies the log date to use. See "Log configuration" above for the available formats.

Example:

$ mvn docker:logs -Ddocker.follow -Ddocker.logDate=DEFAULT

External Configuration

For special configuration needs there is the possibility to get the runtime and build configuration from places outside the plugin's configuration. This is done with the help of <external> configuration sections which at least has a <type> subelement. This <type> element selects a specific so called "handler" which is responsible for creating the full image configuration. A handler can decided to use the <run> and <build> configuration which could be provided in addition to this <external> section or it can decide to completely ignore any extra configuration option.

A handler can also decide to expand this single image configuration to a list of image configurations. The image configurations resulting from such a external configuration are added to the regular <image> configurations without an <external> section.

The available handlers are described in the following.

Property based Configuration

For simple needs the image configuration can be completely defined via Maven properties which are defined outside of this plugin's configuration. Such a property based configuration can be selected with an <type> of props. As extra configuration a prefix for the properties can be defined which by default is docker.

Example:

<image>
  <external>
     <type>props</type>
     <prefix>docker</prefix> <!-- this is the default -->
  </external>
</image>

Given this example configuration a single image configuration is build up from the following properties, which correspond to corresponding values in the <build> and <run> sections.

  • docker.alias Alias name
  • docker.assemblyDescriptor Path to the assembly descriptor when building an image
  • docker.assemblyDescriptorRef Name of a predefined assembly to use.
  • docker.bind.idx Sets a list of paths to bind/expose in the container
  • docker.capAdd.idx List of kernel capabilities to add to the container
  • docker.capDrop.idx List of kernel capabilities to remove from the container
  • docker.command Command to execute. This is used both when running a container and as default command when creating an image.
  • docker.domainname Container domain name
  • docker.dns.idx List of dns servers to use
  • docker.dnsSearch.idx List of dns search domains
  • docker.entrypoint Container entry point
  • docker.env.VARIABLE Sets an environment variable. E.g. <docker.env.JAVA_OPTS>-Xmx512m</docker.env.JAVA_OPTS> sets the environment variable JAVA_OPTS. Multiple such entries can be provided. This environment is used both for building images and running containers. The value cannot be empty.
  • docker.exportDir Directory name for the exported artifacts as described in an assembly (which is /maven by default).
  • docker.extraHosts.idx List of host:ip to add to /etc/hosts
  • docker.from Base image for building an image
  • docker.hostname Container hostname
  • docker.links.idx defines a list of links to other containers when starting a container. idx can be any suffix which is not use except when idx is numeric it specifies the order within the list (i.e. the list contains first a entries with numeric indexes sorted and the all non-numeric indexes in arbitrary order). For example <docker.links.1>db</docker.links.1> specifies a link to the image with alias 'db'.
  • docker.memory Container memory (in bytes)
  • docker.memorySwap Total memory (swap + memory) -1 to disable swap
  • docker.name Image name
  • docker.portPropertyFile specifies a path to a port mapping used when starting a container.
  • docker.ports.idx Sets a port mapping. For example <docker.ports.1>jolokia.ports:8080<docker.ports.1> maps the container port 8080 dynamically to a host port and assigns this host port to the Maven property ${jolokia.port}. See Port mapping for possible mapping options. When creating images images only the right most port is used for exposing the port. For providing multiple port mappings, the index should be count up.
  • docker.registry Registry to use for pushing images.
  • docker.restartPolicy.name Container restart policy
  • docker.restartPolicy.retry Max restrart retries if on-failure used
  • docker.user Container user
  • docker.volumes.idx defined a list of volumes to expose when building an image
  • docker.volumesFrom.idx defines a list of image aliases from which the volumes should be mounted of the container. The list semantics is the same as for links (see above). For examples <docker.volumesFrom.1>data</docker.volumesFrom.1> will mount all volumes exported by the data image.
  • docker.wait.url URL to wait for during startup of a container
  • docker.wait.time Amount of time to wait during startup of a container (in ms)
  • docker.wait.log Wait for a log output to appear.
  • docker.wait.shutdown Time in milliseconds to wait between stopping a container and removing it.
  • docker.workingDir Working dir for commands to run in

Any other <run> or <build> sections are ignored when this handler is used. Multiple property configuration handlers can be used if they use different prefixes. As stated above the environment and ports configuration are both used for running container and building images. If you need a separate configuration you should use explicit run and build configuration sections.

Example:

<properties>
  <docker.name>jolokia/demo</docker.name>
  <docker.alias>service</docker.alias>
  <docker.from>consol/tomcat:7.0</docker.from>
  <docker.assemblyDescriptor>src/main/docker-assembly.xml</docker.assemblyDescriptor>
  <docker.env.CATALINA_OPTS>-Xmx32m</docker.env.CATALINA_OPTS>
  <docker.ports.jolokia.port>8080</docker.ports.jolokia.port>
  <docker.wait.url>http://localhost:${jolokia.port}/jolokia</docker.wait.url>
</properties>

<build>
  <plugins>
    <plugin>
      <groupId>org.jolokia</groupId>
      <artifactId>docker-maven-plugin</artifactId>
      <configuration>
        <images>
          <image>
            <external>
              <type>props</type>
              <prefix>docker</prefix>
            </external>
          </image>
        </images>
      </configuration>
    </plugin>
  </plugins>
</build>

Registry handling

Docker uses registries to store images. The registry is typically specified as part of the name. I.e. if the first part (everything before the first /) contains a dot (.) or colon (:) this part is interpreted as an address (an optionally port) of a remote registry. This registry (or the default index.docker.io if no registry is given) is used during push and pull operations. This plugin follows the same semantics, so if an image name is specified with a registry part, this registry is contacted. Authentication is explained in the next section.

There are some situations however where you want to have more flexibility for specifying a remote registry. This might be, because you do not want to hard code a registry within the pom.xml but provide it from the outside with an environment variable or a system property.

This plugin supports various ways for specifying a registry:

  • If the image name contains a registry part, this registry is used unconditionally and can not be overwritten from the outside.
  • If an image name doesn't contain a registry, then by default the default Docker registry index.docker.io is used for push and pull operations. But this can be overwritten through various means:
    • If the <image> configuration contains a <registry> subelement this registry is used.
    • Otherwise, a global configuration element <registry> is evaluated which can be also provided as system property via -Ddocker.registry.
    • Finally a environment variable DOCKER_REGISTRY is looked up for detecting a registry.

Example:

<configuration>
  <registry>docker.jolokia.org:443</registry>
  <images>
    <image>
      <!-- Without an explicit registry ... -->
      <name>jolokia/jolokia-java</name>
      <!-- ... hence use this registry -->
      <registry>docker.consol.de</registry>
      ....
    <image>
    <image>
      <name>postgresql</name>
      <!-- No registry in the name, hence use the globally 
           configured docker.jolokia.org:443 as registry -->
      ....
    </image>
    <image>
      <!-- Explicitely specified always wins -->
      <name>docker.example.com:5000/another/server</name>
    </image>
  </images>
</configuration>

There is some special behaviour when using an externally provided registry like described above:

  • When pulling, the image pulled will be also tagged with a repository name without registry. The reasoning behind this is that this image then can be referenced also by the configuration when the registry is not specified anymore explicitely.
  • When pushing a local image, temporarily an tag including the registry is added and removed after the push. This is required because Docker an only push registry-named images.

Authentication

When pulling (via the autoPull mode of docker:start) or pushing image, it might be necessary to authenticate against a Docker registry.

There are three different ways for providing credentials:

  • Using a <authConfig> section in the plugin configuration with <username> and <password> elements.
  • Providing system properties docker.username and docker.password from the outside
  • Using a <server> configuration in the the ~/.m2/settings.xml settings

Using the username and password directly in the pom.xml is not recommended since this is widely visible. This is most easiest and transparent way, though. Using an <authConfig> is straight forward:

<plugin>
  <configuration>
     <image>consol/tomcat-7.0</image>
     ...
     <authConfig>
         <username>jolokia</username>
         <password>s!cr!t</password>
     </authConfig>
  </configuration>
</plugin>

The system property provided credentials are a good compromise when using CI servers like Jenkins. You simply provide the credentials from the outside:

mvn -Ddocker.username=jolokia -Ddocker.password=s!cr!t docker:push

The most secure and also the most mavenish way is to add a server to the Maven settings file ~/.m2/settings.xml:

<servers>
  <server>
    <id>registry.hub.docker.io</id>
    <username>jolokia</username>
    <password>s!cr!t</password>
  </server>
  ....
</servers>

The server id must specify the registry to push to/pull from, which by default is central index registry.hub.docker.io. Here you should add you docker.io account for your repositories.

Password encryption

Regardless which mode you choose you can encrypt password as described in the Maven documentation. Assuming that you have setup a master password in ~/.m2/security-settings.xml you can create easily encrypted passwords:

$ mvn --encrypt-password
Password:
{QJ6wvuEfacMHklqsmrtrn1/ClOLqLm8hB7yUL23KOKo=}

This password then can be used in authConfig, docker.password and/or the <server> setting configuration. However, putting an encrypted password into authConfig in the pom.xml doesn't make much sense, since this password is encrypted with an individual master password.