Swarm Web App Demo Cluster: Voting App
JavaScript Shell Java HTML CSS Ruby Python
Switch branches/tags
Nothing to show
Clone or download
Latest commit 677a332 Mar 4, 2016
Permalink
Failed to load latest commit information.
AWS Remove OPTS Mar 4, 2016
Vagrant Change pg->store, web01->frontend01 Feb 6, 2016
results-app
vote-worker
web-vote-app Removed unnecessary files Feb 6, 2016
.gitignore Ignore the .vagrant directory that gets created by vagrant users Jan 14, 2016
README.md
cluster-detailed.png Added rough diagram of cluster with more details (IPs, ports, etc) Jan 12, 2016
cluster.png
docker-compose.override.yml And in the override file as well. Feb 9, 2016
docker-compose.yml Use a version string not int. Feb 9, 2016

README.md

Swarm Example Cluster: Microservices App

This is a sample Swarm cluster that illustrates how Swarm can be used as the foundation for a high-traffic microservice-architecture web application. It is based on the Docker Cats-vs-Dogs voting example application, but re-architected to accomodate arbitrarily large scale through the use of parallel vote capture frontends and asynchronous background workers processing each vote.

Use Case

Imagine that your company is planning to buy an ad during the Superbowl to drive people to a web survey about whether they prefer cats or dogs as pets. (Perhaps your company sells pet food.) You need to ensure that millions of people can vote nearly simultaneously without your website becoming unavailable. You don't need exact real time results because you will announce them the next day, but you do need confidence that every vote will eventually get counted.

Architecture

An Interlock load balancer (ha_proxy plugin) sits in front of N web containers, each of which runs a simple Python (Flask) app that accepts votes and queues them into a redis container on the same node. These N web (+ redis) nodes capture votes quickly and can scale up to any value of N since they operate independently. Any level of expected voting traffic can thus be accomodated.

Asynchronously, M background workers running on separate nodes scan through those N redis containers, dequeueing votes, de-duplicating them (to prevent double voting) and committing the results to a single postgres container that runs on its own node.

Cluster Diagram

(Detailed cluster diagram with port numbers in ./cluster-detailed.png)

Usage

This cluster can be deployed on either Vagrant and AWS. A CloudFormation template (for AWS) and a Vangrantfile (for Vagrant) are included.

For AWS deployment: start at AWS/HOWTO.TXT, which will guide you through other text files documenting the various steps to set up the cluster and the application on AWS.

For Vagrant deployment: start at Vagrant/HOWTO.TXT, again following the pointers to other text files and scripts.