This project is an implementation of an External Containerizer for Apache Mesos, that allows Mesos Executors/Tasks to be launched inside a Docker container. This is especially useful as a mechanism for managing system dependencies, since you no longer need to ensure all of the Mesos slaves have everything installed.

Note: The External Containerizer is an unreleased feature of Mesos. To run this, mesos 0.19.0 is required.

You can configure various attributes of the containerizer using environment variables. If you wish to modify these, copy ./bin/environment.sh.dist to ./bin/environment.sh and change the values.

First, launch a mesos master.

$ ./bin/mesos-master.sh --ip=127.0.0.1
...

You now need to ensure the slave is configured to use external containerization, and give it the path to the docker containerizer.

$ ./bin/mesos-slave.sh --master=127.0.0.1:5050 \
                       --isolation="external" \
                       --containerizer_path="/path/to/this/repo/bin/docker-containerizer"

With the above slave, any tasks that are sent to the slave must contain container information otherwise they will be unable to run. You can configure a default image to allow users to submit tasks without this information, with --default_container_image.

As of version 0.19.0 a new CommandInfo.ContainerInfo message has been introduced. This message is designed to outline any attributes to pass to the containerizer when launching a task or executor, such as the docker image. If you don't specify this, the default docker image will be used.

Images are specified using the docker:/// URL scheme. For example use docker:///ubuntu:13.04 to launch the 13.04 ubuntu docker image in your container. If you're using a custom private registry, you can specify the registry URL also by using docker://my.registry.com/foo/bar:tag.

Note: Unless you're using one of the pure-language mesos frameworks (not released yet) you'll need to ensure the docker image you use has a recent version of Mesos installed. This is to allow running executors to gain access to the Mesos native libraries.

message TaskInfo {
  ...
  optional CommandInfo command = 7;
  ...
}

message CommandInfo {
  ...
  // Describes a container.
  // Not all containerizers currently implement ContainerInfo, so it
  // is possible that a launched task will fail due to supplying this
  // attribute.
  // NOTE: The containerizer API is currently in an early beta or
  // even alpha state. Some details, like the exact semantics of an
  // "image" or "options" are not yet hardened.
  // TODO(tillt): Describe the exact scheme and semantics of "image"
  // and "options".
  message ContainerInfo {
    // URI describing the container image name.
    required string image = 1;

    // Describes additional options passed to the containerizer.
    repeated string options = 2;
  }

  // NOTE: MesosContainerizer does currently not support this
  // attribute and tasks supplying a 'container' will fail.
  optional ContainerInfo container = 4;
  ...
}

The ./example folder contains a Vagrantfile that launches a vagrant VM ready and waiting for testing the containerizer.

• Installs docker
• Downloads and compiles mesos (at the right version) into /opt/mesos
• Includes the containerizer code into /opt/mesos-docker-containerizer

The VM doesn't launch a running mesos master or slave, you'll need to log in via vagrant ssh and use the /opt/mesos/build/bin/* tools to do that yourself.