Observability in Selenium

A project to showcase Selenium 4's Tracing capability using OpenTelemetry APIs(Jaeger) with Selenium Grid

Selenium 4

It has number of new exciting features and one such is a cleaner code for Selenium Grid along with support for distributed tracing via OpenTelemetry APIs. This is pretty exciting and important feature for the admins and devops engineers to trace the flow of control through the Grid for each and every command.

Distributed tracing has two parts:

Code instrumentation: Adding instrumentation code in your application to produce traces. The major instrumentation parts are done neatly by the developers of Selenium project, which leaves us to consume it by using Selenium Grid start-up command along with Jaeger.

Collection of data and providing meaning over it, Jaeger has a UI which allows us to view traces visually well.

Steps to start tracing your tests,

Start Jaeger via docker(as its easy)

Instrument your Selenium Grid start-up command with Jaeger tracing as in start-grid-distributed.sh distributed mode.

Now execute your tests, and navigate to http://localhost:16686/ to view the outputs.

Pre-requisites

Assuming you have docker running on your machine,

1. Install Coursier via homebrew brew install coursier/formulas/coursier
2. Install Jaeger via docker
3. Selenium-server.jar refers to the latest alpha version of selenium releases (Tested with Apha 5)

Start Jaeger via docker server

The simplest way to start the all-in-one is to use the pre-built image published to DockerHub (a single command line).

$ docker run --rm -it --name jaeger \
    -p 16686:16686 \
    -p 14250:14250 \
    jaegertracing/all-in-one:1.17

You can then navigate to http://localhost:16686 to access the Jaeger UI.

Instrument your Selenium Grid command

We're going to add support for Open Telemetry API's(one of the many ways to do distributed tracing) using Coursier to generate a full classpath, when started this way the selenium server will inform you that it has found a tracer on stdout.

Refer start-grid-distributed.sh if you want to start Grid in distributed mode.

curl http://localhost:4444/status to check if your grid deployment is ready

Execute your tests

Point your tests as in DistributedTracingExamples Class and navigate to http://localhost:16686/ to view the outputs.

Under services look up for Selenium-router and notices actions for each calls made by your tests. An example below

References:

• Tracing Info command
• Jaeger guide
• Three Pillars of Observability

A special thanks to Manoj Kumar and Puja Jagani for knowledge sharing on these capabilities.