This is the source code for the demo that I used when I presented this talk to

• PuppetConf 2012
• again at OSDC 2013
• at PuppetCamp Sydney 2013
• Sysadmin Miniconf at linux.conf.au 2014
• using Prometheus as a demo at Monitorama 2015
• again at linux.conf.au 2016
• Velocity SC 2016
• SRECon Americas 2017
• incorporating SLO Burn alerting for Monitorama 2018, SRECon Asia 2018, Velocity SJ 2018, and Velocity NY 2018.
• SLOconf Sydney 2023

There are Git tags for each presentation so you can jump back to each demo if that pleases you.

The URL for the video from PuppetConf 2012 is http://youtu.be/eq4CnIzw-pE

The original slide deck is at https://docs.google.com/presentation/d/1uTLggLR5HICnSyhTJyQWNeYWZ6niHyCsup7wNFByex4/pub

I presented an abridged version to the Sysadmin Miniconf at Linux.conf.au 2014, the revised slide deck is here:

https://docs.google.com/presentation/d/1Dq4eRUlkONnVnnXg6M_ZSi6xBLEwe7kjwjx74vFL1N4/pub

Monitorama 2015 slides: https://docs.google.com/presentation/d/1X1rKozAUuF2MVc1YXElFWq9wkcWv3Axdldl8LOH9Vik/edit

linux.conf.au 2016 slides: https://docs.google.com/presentation/d/1NziwSTwuz91fqsFhXeOGwyhFUoT6ght1irA_0ABLPU0/edit

The code is likely to break without notice. At best I can promise you it worked at the time I gave the most recent demo, with the dependencies available at the time. YMMV.

The demo is of a mock service, a web application frontend, composed of a cluster of application servers and a single loadbalancer. The loadbalancer is not very good, and the application servers fail often. An antagonistic load generator drives them past their capable limits.

Prometheus is the metrics collector and alerting engine used in this example. Zipkin is used for capturing traces if you choose to add it.

The demo uses Podman Compose to start up the environment. You'll get a Grafana with the SLO Dashboard, a Prometheus, a Servers image containing the fake cluster and load balancer, and a Zipkin.

./load.sh requires ab (ApacheBench) from the Apache webserver tools (apache2-utils). ./load-nice.sh is the non-antagonistic version.

./1000concurrent.sh keeps 1000 concurrent HTTP sessions open to the loadbalancer. Because the system latency is about 1s average, this means around 100 qps. Thanks, Little's Law!

./replace.sh takes the PID of one backend server and replaces it with a backend that fails more often. Killing this script causes the entire backend to die.

The subdirectory prom contains the main config and rules for the Prometheus tools, likewise graf for Grafana.

The R code is from the version back in 2012 when Prometheus didn't exist, and I couldn't yet talk about Borgmon. ;-) I like to keep it here as a reminder.

This code is available under the Apache v2 license.

The first demo series is based around the idea of alerting from timeseries, not from check scripts.

Make sure you have golang-github-containernetworking-plugin-dnsname installed for the container networking DNS support.

Start the containers with podman-compose up, and then start the demo with ./load-nice.sh. Go to the prometheus console at http://localhost:9090/alerts and observe no alerts being fired.

Stop load-nice.sh and start up ./load.sh. The system should quickly cascade to failure and you'll get some alerts firing.

The alerts are defined in prom/tasks.rules, prom/errors.rules, and prom/latency.rules.

The second demo shows how to avoid all those alerts and focus on the overall health of the system, i.e. by having defined service level objective, let us know when that objective is in danger of being missed.

Start the system with docker-compose up, and then run ./1000concurrent.sh.

Look at the Grafana console at http://localhost:3000 and see the SLO Burn Demo console. The Burn rate vs Threshold chart shows you the current short term burn rate vs the estimated threshold. The threshold estimate is based on a prediction of the total events over the SLO measurement period, but at a consumption rate faster the Burn Period, i.e. page if we are burning at a rate that would consume the entire error budget for one month in the next day. The maths can be seen in prom/slo.rules.yml

To demo a failure of a backend, you need to log into the servers container and run the replace.sh script with the PID of the old backend we want to cause to fail.

podman exec -it blts_servers_1 sh to get a shell in the container. Do a ps | grep "[p]ort 8009" to find the PID of the server, and then run ./replace <pid>.

On the dashboard, you'll see a higher failure rate, but not yet an alert because the SLO burn rate has not been breached yet.

^C the replace script, stopping that backend server entirely, and there should be a high enough failure rate to trigger the SLO burn alert on the console.

This is not an officially supported Google product

There is a similar project at https://github.com/google/prometheus-slo-burn-example