This is a recap about how we use the isolation of containers and the power, portability and simplicity of Docker for providing tooling as a service via executable images using DCOS-CLI as an example. True story!

The problem:

  • We want to install Mesos Frameworks.
  • We want to deploy apps with Marathon.
  • We want to automate the installation of Mesos Frameworks.
  • We want to automate the deployment of apps.

The pain!

  • DCOS-CLI from Mesosphere is the best solution for the first two problems but we need to follow all the steps to install it.
  • We need to make sure our environment is suitable to install and run it so it has all the required dependencies.
  • We need to make sure every environment where we want to run it is suitable to install and run it so every environment has all the required dependencies.
  • We need to ensure all the dependencies and any executables comply with security requirements, as the attack vector can be quite extensive.

The solution:

  • To offer DCOS-CLI as a service that can be executed with zero dependencies with the specific environment.
  • To consume this service from a given automation tool like Ansible.

But how?

SOURCES=${SOURCES:-'[ "", "",]'}
  • The container creates a temporary config file from your environment variables, executes your command and dies. Check out the source code here.
docker run -v `pwd`/chronos_config:/config \
           -e MESOS_MASTER_URL='' \
           -e MARATHON_URL='' \
           -it capgemini:dcos-cli package install --options=config --yes chronos
  • Now it’s up to you how to automate it. We use ansible and the Frameworks role for Apollo which looks something like this:

# defaults file for frameworks
frameworks_dcos_cli_image: capgemini/dcos-cli
frameworks_zk_master_peers: "zk://{{ zookeeper_peers_nodes }}/mesos"
frameworks_mesos_master_url: "http://{{ ansible_ssh_host }}:5050"
frameworks_marathon_url: "http://{{ ansible_ssh_host }}:8080"
frameworks_sources: '["",]'
  - cassandra
  - chronos

- name: "install dcos-cli package"
  when: "frameworks_{{ item }}_enabled | bool"
  run_once: true
    name: "{{ item }}"
    image: "{{ frameworks_dcos_cli_image }}"
    state: started
    command: "package install --options=/config --yes {{ item }}"
    - "/tmp/{{ item }}-config:/config"
      MESOS_MASTER_URL: "{{ frameworks_mesos_master_url }}"
      MARATHON_URL: "{{ frameworks_marathon_url }}"
      SOURCES: "{{ frameworks_sources }}"
    - "{{ item }}"
    - "{{ frameworks_list }}"

The benefits:

  • Reduced impacting surface.
  • Only one dependency with the run time container, i.e Docker.
  • Crazily easy to integrate with other automation tools!
  • Reusable.
  • Build once, Run everywhere!

At the time of writing this post, Mesosphere, the creators of DCOS-CLI among such other amazing tools around Mesos, are working on their own image for DCOS-CLI

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