cerberus

Automatic alert system for telemetry histograms.

Cerberus detects changes in the distribution of histograms (histogram regressions), and posts alerts for these to the medusa alert service.

Cerberus is also responsible for sending out email reminders for histograms that are expiring in upcoming versions.

Development and deployment

To start hacking on your local machine:

vagrant up
vagrant ssh

To deploy cerberus on AWS:

ansible-playbook ansible/deploy.yml -i ansible/inventory [ --private-key /path/to/mykey.pem ]

Note that the deployment requires medusa to be deployed.

Code Overview

run.sh is a shell script that will set up all the dependencies, then do a full run of the Cerberus detectors. These are the components used in the script:

• exporter/export.js downloads the histogram evolutions from the v4 aggregates API.
  • This script uses telemetry-next-node in order to access Unified Telemetry data.
• The code for detecting regressions lives in alert/alert.py. This file is intended to be run as a script.
  • This is a script that reads histogram definitions from Histograms.json (which is downloaded automatically by run.sh).
  • Detected regressions are written out to dashboard/regressions.json.
• alert/post.py reads in new regressions from dashboard/regressions.json, and posts alerts to Medusa with this data.
  • Posting new alerts to Medusa is done using alert/poster.py.
  • By default, the Medusa server URL is set to localhost:8080 - it expects to be on the same machine as the Medusa server. This can be changed by editing alert/post.py.
• alert/expiring.py is the histogram expiry detector - it notifies people via email when histograms are expiring soon.
  • Some configurable number of days before the versions where histograms are set to expire, it sends out emails using Amazon SES to watchers, and the dev-telemetry-alerts mailing list.
• dashboard/ contains a debugging/development dashboard for viewing detected regressions. It is intended to be hosted via GitHub Pages or a similar static hosting solution.