Sensu is a distributed scalable monitoring solution, written in Ruby with a JVM option for Enterprise users. It has multi-master redundancy using a message broker architecture to distribute messages from clients. Clients are configured to either push messages to the master, or provide results in response to requests from the masters.

Key Points

  • Compatible with Nagios style checks
  • Lightweight agent and servers
  • Uses RabbitMQ or Redis for message brokers
  • Very simple configuration through JSON
  • Uses Redis as a key/value database
    • Can be purged completely with no lasting impact to Sensu
    • Maintains last 20 events for Flap detection
    • Maintains list of ‘silenced’ alerts
    • Maintains list of ‘known’ clients - to allow alerts when machines stop responding
  • Great community support from freenode#sensu

Getting Started

The online getting started documentation is a perfect place to begin your experimentation with Sensu.

It basically boils down to:

  1. Install Redis, RabbitMQ and Sensu servers
  2. Configure the various components to talk to eachother
  3. Define your first checks and you’re done
  4. Optionally install a dashboard such as Uchiwa, (recommended)

Sensu Community Plugins

You’ll find that there exist lots of sensu checks already created by the Sensu community, many of these have been placed onto GitHub for others to easily find.

Check out for more information on the scripts and checks that are avaliable.

Additional Resources

WTF is Sensu presentation slides

Slides from a presentation I gave at Bristol DevOps which explains the importance and prioritisation you need to give for effective monitoring of your product, and its impact on your customers.

Docker and Sensu

A set of sensu docker containers that can help provision automated checks of docker containers

Mosaic - A Dashboard I Made

A simple information radiator for use with Sensu that uses the Uchiwa (< 0.11) api to provide a TV sized board that can let users quickly know the state of health for a large number of machines at once.

Mosaic Screenshot