Docker Support

Roboconf has a target implementation for Docker.
This handler makes Docker seen as a kind of IaaS. Roboconf may create and manage Docker containers, that run Roboconf agents (just like VMs) and can be used as deployment targets.

This is useful for tests and demonstrations.
Not for real productions.

To install it, open the DM’s interactive mode and use one of the following options.
With the roboconf:target command:

# The version will be deduced automatically by the DM
roboconf:target docker

Or with the native Karaf commands:

# Here in version %v_SNAP%
bundle:install --start mvn:net.roboconf/roboconf-target-docker/%v_SNAP%

Sample target.properties.
Just copy / paste and edit.

# Configuration file for Docker
handler = docker

# Provide a meaningful description of the target
id = a unique identifier
name = 
description = 

# Docker API
# docker.endpoint = tcp://localhost:4243
# docker.image = roboconf/roboconf-agent:<version> 

# docker.user = 
# docker.password = 
# docker.email = 
# docker.version = 

# Image Generation
# docker.generate.image.from = ./img

Here is a complete description of the parameters for Docker.
Let’s begin with general parameters.

\<version\> is the version of the DM.
If the DM is a snapshot version, then LATEST is retained.

If you use your own image, you should extend the official one for Roboconf agents.
If the Docker image is not found, Roboconf will try to generate it from a Dockerfile that is supposed to be provided. If no Dockerfile is provided, an error will be thrown. Let’s take a look at parameters related to image generation.

You should use our official images as a work base.

Default Run Options

This handler starts containers with the following elements:

• A shared volume that contain dynamic parameters.
• An environment variable (AGENT_PARAMETERS) which sets up the agent configuration in the container.
• An environment variable (RBCF_VERSION) which is the version of the DM.

Docker Configuration

See Roboconf’s Docker tips for details about installing and preparing Docker for Roboconf.
You will also find a reminder about basic Docker commands.

Docker Options

Docker CLI and Docker’s remote API allows you to pass various options.
Some of these options can also be passed via Roboconf to create a new container (i.e. docker run…).

These options are only used when Roboconf creates a container.
Other operations, like creating an image, cannot use them.

Since these options are passed with the Java REST API, Roboconf only supports a subset of options.
Only those of type int, long, boolean, string, array of string and array of capabilities are supported.
These options must be prefixed with docker.option.run..

Let’s take a look at examples.

# Set the host name
docker.option.run.hostname = some host name

# Set the CPU share
docker.option.run.cpushares = 512
docker.option.run.cpu-shares = 512

# Attach the standard error with the container
# (probably useless with Roboconf but this is for the example)
docker.option.run.attachstderr = true
docker.option.run.attach-stderr = true

# Add capacilities
docker.option.run.capadd = SYS_PTRACE, AUDIT_CONTROL
docker.option.run.cap-add = SYS_PTRACE, AUDIT_CONTROL

# Remove capabilities
docker.option.run.capdrop = MKNOD, AUDIT_CONTROL
docker.option.run.cap-drop = MKNOD, AUDIT_CONTROL

Options can be found in the remote API’s guide.
Given the way Roboconf passes these options to the REST clients, it is possible some options fail to be set. Complex ones are not supported at all (e.g. ExposedPorts).

If you need support for new options, or if one does not work, please submit a feature request and/or a bug report.

Docker Environment Variables

It is possible to pass environment variables when the DM starts a Docker container.
Such variables must be prefixed with docker.option.env.. It is also possible few place holders in values.

Example:

# "VAR=value"
docker.option.env.VAR = value

#  AGENT_APPLICATION_NAME="application name injected by the DM"
docker.option.env.AGENT_APPLICATION_NAME = <application-name>

#  AGENT_SCOPED_INSTANCE_PATH="scoped instance path injected by the DM"
docker.option.env.AGENT_SCOPED_INSTANCE_PATH = <scoped-instance-path>

#  AGENT_MESSAGING_TYPE="messaging type injected by the DM" (e.g. RabbitMQ)
docker.option.env.AGENT_MESSAGING_TYPE = <scoped-messaging_type>

Notice that there is no place holder for messaging properties.
Also remember the DM injects the AGENT_PARAMETERS environment variable.

Privileges

docker.option.run.cap-add can be used to change privileges.
Indeed, some Software component cannot be installed with the default configuration.
As an example, if set to SYS_PTRACE, then Roboconf will execute…

docker run --cap-add SYS_PTRACE id /usr/local/roboconf-agent/start.sh

Such permissions are sometimes necessary.
See these discussions on Github for additional information.

• How to use init script
• Add a property to pass options to run Docker containers

Extending the Official Image

There are cases where you want to extend the official image to install automatically some add-ons. It can be installing new system packages…

FROM roboconf/roboconf-agent:${RBCF_VERSION}
RUN apt-get install -y my-package1 my-package2

… or installing extensions for a Roboconf agent.
This second case is a little more complex. Let’s start with a simple scenario: we only want to deploy something that runs in Karaf but does not depend on Roboconf libraries. Example: Karaf Decanter (a monitoring solution).

FROM roboconf/roboconf-agent:${RBCF_VERSION}

# Add a new repo
RUN echo "mvn:org.apache.karaf.decanter/apache-karaf-decanter/LATEST/xml/features" \
	>> /opt/roboconf-karaf-dist-agent/etc/org.apache.karaf.features.repos.cfg

# Add a list of features to enable / install at startup
RUN sed -i /featuresBoot\s*=\s*/featuresBoot = management, decanter-collector-jmx, / \
	/opt/roboconf-karaf-dist-agent/etc/org.apache.karaf.features.cfg

Let’s take a look now about a feature that would depend on Roboconf.
To solve deployment ordering, you need to create a Karaf feature first, that depends on the roboconf-agent one.

<?xml version="1.0" encoding="UTF-8"?>
<features 
		name="generated-by-roboconf"
		xmlns="http://karaf.apache.org/xmlns/features/v1.3.0"
		xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://karaf.apache.org/xmlns/features/v1.3.0 http://karaf.apache.org/xmlns/features/v1.3.0">

	<feature name="roboconf-agent-additions" version="1.0" description="Generated by Roboconf (Docker Target)" install="auto">
		<feature>roboconf-agent</feature>

		<bundle>http://my-server/bundle1.jar</bundle>
		<bundle>http://my-server/bundle2.jar</bundle>
		<bundle>file:/opt/roboconf-karaf-dist-agent/my-agent-extensions/bundle3.jar</bundle>
	</feature>
</features>

Put it within the same directory than your Dockerfile.

FROM roboconf/roboconf-agent:${RBCF_VERSION}

# Copy a local dependency
# (assuming all the other ones are available remotely) 
RUN mkdir -p /opt/roboconf-karaf-dist-agent/my-agent-extensions
ADD bundle3.jar /opt/roboconf-karaf-dist-agent/my-agent-extensions/

# Copy the feature  in the "deploy" folder
# (its name must be "feature.xml")
COPY my-feature.xml /opt/roboconf-karaf-dist-agent/deploy/