Cauchy is Riemann's colleague
Riemann is a powerful event processing engine, in which rules are written in Clojure. Riemann Events are data structures conveying statuses, metrics or logs sent to the server by Riemann Clients.
Riemann is very interesting in a cloud environment because it can be used to monitor systems without having to store and update an inventory, unlike traditional solutions (nagios, zabbix, etc..) which only handle hosts that were defined in the system first. Since we use instance auto-scaling this is a must-have.
Riemann had many input and output plugins, allowing a rich ecosystem to thrive on your collected data. As an example, we use Graphite interop at linkfluence.
Although there are a lot of clients for the Riemann protocol, we didn't find an already existing piece of software to act as an agent (an autonomous agent gathers and then sends metrics and statuses to Riemann). That is why we started working on Cauchy.
Cauchy is a Riemann system agent with batteries included. Once deployed on your servers, we hope it'll provide a better monitoring than the usual solutions. It allows inventory-less, decentralized processing of your statuses and metrics (for both system and application monitoring). It is extensible with community-provided or custom plugins to monitor specific application data, and these extensions can benefit from the advanced capabilities of Clojure whereas with classic monitoring plugins we're often hindered by bash scripting.
Cauchy is basically a job scheduler, in which jobs are the periodic checks that you'd like configure on your host. Jobs are clojure functions.
Jobs can be :
- built-in into cauchy,
- defined inline in the configuration,
- defined in some extra JARs provided by the community (see examples of extra cauchy-jobs below)
- or defined in a JAR provided by your own means.
Jobs can be scheduled with intervals way lower than a minute, and Cauchy spreads the load randomly to prevent swarming your Riemann server with events.
Cauchy provides, out of the box, the usual checks (jobs) that you expect from a server monitoring solution.
- CPU load (1 minute, 5 minutes, 15 minutes)
- Memory usage
- Swap Usage
- Disk usage for all mountpoints
- Disk IO throughput
- Network IO throughput
- Check for process existence
Additionally, I wrote a few extra jars providing additional checks to cauchy :
Please have a look at them if you intend to write your own jobs. Please get in touch if you defined a job that can be useful to others and want to share.
{:service "Service1 check"
:interval 12 :type :clj
:job-fn (fn [] )}
A job must return a map, or a seq of maps if returning more than one event, with the following keys :
:state ;; Can be skipped if only a metric
:metric ;; Optional, default : not sent
:description ;; Optional, default : not sent
:ttl ;; Optional, default : (* 2 interval)
:service ;; Optional, default : (:service job)
:host ;; Optional, default : hostname
:tags ;; Optional, default : not sent
This return map is merged with the :defaults from the configuration file before being sent to the Riemann server.
Cauchy is a trapperkeeper application and benefits from trapperkeeper's configuration system to easily load templates:
/usr/bin/java -Xmx256m -cp /opt/cauchy/jar/cauchy/lib/cauchy-jobs-kestrel-0.1.0-SNAPSHOT-standalone.jar:/opt/cauchy/jar/cauchy/cauchy-0.1.0-SNAPSHOT-standalone.jar puppetlabs.trapperkeeper.main --config /opt/cauchy/conf/cauchy.edn,/opt/cauchy/conf/cauchy-profiles
- Web server to show current (local) state of the agent.
- route to reload config (ou signal?)
- buffer events when they cannot be sent to riemann
Augustin-Louis Cauchy (1789 – 1857) was a french mathematician, contemporary of Bernhard Riemann. They often worked on similar areas of mathematics.
Copyright © 2014 Philippe Guillebert
Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.