ansible-smartstack

SmartStack is an automated service discovery and registration framework. This ansible role installs airbnb smartstack, which includes following components

• ruby
• nerve : for service registration.
• synapse : for service discovery.
• serf : for cluster membership
• HAProxy : for load balancing

For more information on smartstack This role uses the getyourguide smartstack fork.
The role will use serf instead of zookeeper.

How it Works

• Assumption : There are two services, Service-A and Service-B. There are n numbers of Service-A which Service-B connects it.
• Nerve run on every instance of Service-A and announces that service is up and running via serf
• Serf communicates this information to the other members via gossip protocol
• Synapse which runs on Service-B get this information from serf and and configures HAProxy
• Service-B now can connect to list of Service-A. If there is a new instance of Service-A this will be added into the HAProxy.
• If one of them fail will be removed from the HAProxy.

That means, Serf is required both for nerve and synapse and Haproxy is required only for synapse.

Requirements

This role is tested with ubuntu 12.04 and ansible 1.7

Role Variables

Please check following files for variables

default/main.yml
vars/services.yml

Usage

Installation of synapse and nerve are have to be explicitly stated in your playbook.

	nerve_install           : True

If you would like to install synapse

	synapse_install         : True

You also have to give the list of services that you want to make available, for instance if you would like to announce the postgres service

	nerve_selected_services       : [ "postgresql" ]

You also have to give the list of services that you want to connect to / use, for instance if you would like to connect to a memcache service running on another server:

	synapse_selected_services       : [ "memcache" ]

You also need to define the services that you need, an example how services can be defined can be found at

vars/services.yml

Once you define your services you can give the path of your service file as a variable to the this role:

	smartstack_services_files  : "my-services.yml"

Example Playbook

Head to demo directoy Requires Vagrant 1.5 + and ansible 1.8+

vagrant up 3 vagrant images will be created

demo1 (192.168.56.150)

• postgresql server
• SuperApp
• nerv
• serf

demo2 (192.168.56.151)

• superApp
• synapse
• serf
• haproxy

demo3 (192.168.56.152)

• nginx
• synapse
• serf
• haproxy

Check superApp

http://192.168.56.152 and refersh a couple of times

###To check serf members From demo1 or demo2 type serf members

###To check haproxy stats page http://192.168.56.151:3212/ on demo2 http://192.168.56.152:3212/ on demo3

Simulate failure serf failure

On demo1 type sudo service serf stop then on demo2 serf members

Enable back serf on demo1 by typing sudo service serf stop

Simulate postgresql faliure

on demo2 sudo service postgresql stop then head to http://192.168.56.151:3212/

Simulate Applocation faliure

on demo2 sudo service superapp stop then head to http://192.168.56.151:3212/

License

MIT

TODOs

• a service guarantee (runit, monit, ...)

Contributors (sorted alphabetically on the first name)

• Adham Helal
• Engin Yoeyen
• Joé Schaul