Enable and read Selenium Grid 4's built-in OpenTelemetry tracing and structured event logs to debug a distributed Grid session
domain: selenium.dev · 6 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Start the Grid (standalone, hub-and-node, or fully distributed) — tracing/event logging is enabled by default with no extra flag required
Pass --log-level FINE when launching the server jar, since normal spans/events log at FINE while the console default is a coarser level
Read the structured log lines per span/event, which include a trace ID, span ID, span kind, event name, and an attributes object (e.g. HTTP status code, handler class, session ID)
For failures, look for exception-tagged events that add exception type, message, and stack trace fields
Use the server's built-in 'tracing' info command to get setup instructions for exporting traces to a Jaeger backend via OpenTelemetry instead of reading raw console logs
Correlate one session across Grid's distributed components (router, distributor, node) by grepping for its trace ID or session ID
Known gotchas
There's no built-in visualization UI — a separate OpenTelemetry backend such as Jaeger must be run to view traces graphically; the console exporter only prints text/JSON
Normal events log at FINE and errors at a higher level; if your log configuration filters below FINE, tracing output will be invisible without explicitly raising the log level
This instruments Grid's own internal HTTP handling (session creation, routing, distribution), not arbitrary WebDriver commands sent into the browser itself
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