How to Rapidly Deploy DCOS Services with Ansible and Docker

1. Overview of Services and Components

Core services used in the DCOS deployment include Ansible, a test yum repository created with createrepo, a private Docker registry secured by a self‑signed certificate, a simple HTTP server, Docker as the container runtime, cAdvisor for monitoring, HAProxy for load balancing, Keepalived for high availability, MySQL in a master‑slave configuration, custom DCOS UI components, Consul for service discovery and health checks, Zookeeper, Mesos, Marathon, and the DCOS resource manager.

2. Functional Architecture and Logic

Installation scripts first verify whether a service already exists; if it does, the script aborts for manual verification. Key components are:

Test yum repo : lightweight yum source built with createrepo that hosts required RPMs.

Test Docker registry : private registry without authentication, using a self‑signed certificate; all component images are pushed once and reused.

Consul : provides health checks, service discovery, and MySQL master‑slave failover. Services register via the Consul client API, and health checks run locally on each client.

HAProxy : external load balancer that routes traffic to services registered in Consul. HAProxy 1.6 is used to enable dynamic DNS resolution.

MySQL HA : master‑slave pair registers four Consul services (master, slave, and their health checks). When the master disappears, the virtual IP resolves to the slave.

Zookeeper / Mesos / Marathon : referenced for further reading.

3. Dockerizing Services

Typical Dockerfile instructions: FROM – base image RUN – execute shell commands ADD – add files or download archives COPY – copy local files ENTRYPOINT – default container command CMD – default parameters

Reference: https://docs.docker.com/engine/reference/builder/

Example build and run commands:

docker build -t my-zookeeper .

docker run -d --name zookeeper my-zookeeper

4. Installing the Control Host

Start the test yum repository and add a file /etc/yum.repos.d/test.repo pointing to it. Install essential tools:

yum --disablerepo=* --enablerepo=testrepo install -y net-tools iptables ansible

Configure the NTP client as part of the host setup.

5. System Pre‑Installation Checks

Yum repository status

Test Docker registry health

NTP server synchronization

Operating system and kernel version

Filesystem layout

Disk capacity

If any check fails, the installation aborts.

6. Host Initialization

Disable firewalls and SELinux

Configure hostname and DNS resolution

Set up NTP client

Install and configure Docker

Install debugging tools (netstat, dig, etc.)

Verify post‑initialization environment

7. Cluster Initialization with Ansible

Prepare Ansible inventory files describing master nodes, worker nodes, MySQL hosts, Keepalived VIPs, and other roles. Playbooks perform:

Installation of Docker images and service agents (Consul, HAProxy, Keepalived, MySQL, Zookeeper, etc.)

Registration of each service to Consul

Dynamic DNS configuration for HAProxy

MySQL master‑slave registration and health‑based VIP failover

8. Summary

The DCOS deployment is abstracted into two steps: (1) define all services and parameters in a single configuration file; (2) execute the Ansible‑driven installation script. The current solution works for small‑scale clusters; performance improvements are planned for large‑scale host provisioning.

Additional resources:

OpenDockerFile repository: https://github.com/Dataman-Cloud/OpenDockerFile

Related article on container‑based product iteration: http://blog.dataman-inc.com/shurenyun-docker-164/