Running distributed, and what it changes, Selenium Senior

Running distributed, and what it changes

Remote execution multiplies latency, breaks local assumptions, and makes evidence collection the only debugging you have.

What you'll learn

Why latency multiplies when you go remote
What breaks that worked locally
How to debug a failure on a machine you cannot see

A suite that passed reliably on laptops moved to a Grid and became unreliable. No test changed. The team suspected the Grid was broken.

The Grid was fine. Distributed execution changes four things, and each breaks a different assumption.

One: latency multiplies.

Every command is an HTTP round trip, as the protocol lecture explained. Locally that is a millisecond. To a Grid in another data centre it might be 30 to 50ms.

A test making 100 commands goes from 0.1 seconds of protocol overhead to 5 seconds. A suite of 2,000 such tests adds hours.

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