Network

Maven Plugin Networks

For this chapter we will use Simple App With DB - from plugin-db-initial branch.

Auto Create Network

• When dealing with network, we may need to create a network.
• If we create a custom network, we need to create it manually.
• Plugin that we are using can be configured so that custom network can be created automatically.
• Just set <docker.autoCreateCustomNetworks> value to true and you will be all set.

<properties>
    ...
    <docker.autoCreateCustomNetworks>true</docker.autoCreateCustomNetworks>
</properties>

Create a network

• To create a network we use <network> tag.
• <network> has few children.
  • mode: The network mode, which can be one of the following values:
  • name: For mode container this is the container name, which is this image alias. For Mode custom this is the name of the custom network.
  • alias: One or more alias element can be provided which gives a way for a container to be discovered by alternate names by any other container within the scope of a particular network. This configuration only has effect for when the network mode is custom. More than one alias can be given by providing multiple entries.

<image>
    <name>docker-kubernetes:${project.version}</name>
    ...
    <run>
        <network>
            <mode>custom</mode>
            <name>mynet</name>
        </network>
        ...
        <env>
            <DB_URL>
                <![CDATA[ jdbc:mysql://mysql_db:3306/docker_kubernetes?useSSL=false]]>
            </DB_URL>
            <DB_USER>root</DB_USER>
            <DB_PASS>password</DB_PASS>
        </env>
    </run>
</image>
<image>
    <name>mydb:${project.version}</name>
    <alias>mydb</alias>
    ...
    <run>
        <network>
            <mode>custom</mode>
            <name>mynet</name>
            <alias>mysql_db</alias>
        </network>
        ...
        <ports>
            <port>4406:3306</port>
        </ports>
        <env>
            <MYSQL_ROOT_PASSWORD>password</MYSQL_ROOT_PASSWORD>
            <MYSQL_DATABASE>docker_kubernetes</MYSQL_DATABASE>
        </env>
    </run>
</image>

• To add your container in a network, you use <network> tag inside <run> tag.

• <mode> can accept multiple value

  • bridge : Bridged mode with the default Docker bridge (default)
  • host : Share the Docker host network interfaces
  • container : Connect to the network of the specified container. The name of the container is taken from the <name> element.
  • custom : Use a custom network, which must be created before by using docker network create.
  • none : No network will be setup.

• In our case we are using custom, because we want to create our own network.

• <alias> is where we give a way for a container to be discovered by alternate names by any other container within the scope of a particular network.

• Notice: we are using same network on both image configuration. But on mysql part we are giving alias.

• If you build and run the app, and your app will just work.

mode container

• Using mode container you can access your network container using localhost.
• But remember you have one big limitation, you cannot combine this with <ports>.

<images>
    <image>
        <name>docker-kubernetes:${project.version}</name>
        <alias>my-app</alias>
        ...
        <run>
            <network>
                <mode>custom</mode>
                <name>mynet</name>
            </network>
            <ports>
                <port>9090:8080</port>
            </ports>
            <env>
                <DB_URL> <![CDATA[ jdbc:mysql://localhost:3306/docker_kubernetes?useSSL=false ]]> </DB_URL>
                ...
            </env>
        </run>
    </image>
    <image>
        <name>mydb:${project.version}</name>
        <alias>mydb</alias>
        <build>
            <from>mysql:5.7</from>
        </build>
        <run>
            <network>
                <mode>container</mode>
                <name>my-app</name>
            </network>
            ...
        </run>
    </image>
</images>

• We are still using <network> with mode custom on our web app side.
• On database side, we are using mode container but instead of network name we are using our web app name.
• We are using container alias here but you could have used name as well.

dependsOn

• If you want to order which container start first you can use depends_on.
• With the plugin we have <dependsOn> tag.

<image>
    <name>docker-kubernetes:${project.version}</name>
    ...
    <run>
        ...
        <dependsOn>
            <container>mydb</container>
        </dependsOn>
    </run>
</image>
<image>
<name>mydb:${project.version}</name>
<alias>mydb</alias>
...
</image>