(pageextractor-observability)=

# Page Extractor observability

One extraction can cross the parent and content processes, run in several
stages, and depend on a site that behaves differently in a hidden browser. Page
Extractor records each instrumented stage as a Glean event and, while the
profiler runs, as a profiler marker, so you can investigate failures and
performance as one flow.

Each record includes the stage, process, outcome, strategy, and size
information. Nested stages
overlap, so do not add their durations together. A shared flow identifier
connects work across processes and between profiler and telemetry data.

## Investigate an extraction

1. Start the profiler from the toolbar button or `about:profiling`.
2. Run the extraction.
3. Look for `PageExtractor #n` tracks in the marker chart.

Markers are blue for success, red for thrown errors, and yellow for handled
outcomes such as unavailable or empty content. The marker details name the
stage and strategy that produced the outcome. In a hidden browser, pass the
callback's `traceId` into `getText` so loading and extraction stay in the same
flow.

[Instrumenting JavaScript](/tools/profiler/instrumenting-javascript.md) explains
the profiler mechanism.

## Telemetry

Finished stages record `page_extractor.phase` events in the `page-extractor`
ping, subject to Glean collection settings. The event holds operational
information such as outcome, duration, strategy, and coarse size counts. It
holds no page text, URLs, image data, or error messages. The ping has no client
identifier and uses OHTTP.

When you analyze the events, pick the stage that represents the behavior you
are measuring. Counting every nested stage counts one failure more than once.
Group records by flow identifier to follow a request across processes.

The events module and the Glean metrics and pings definitions next to it define
the phases and fields. The design history is in
[bug 2065318](https://bugzilla.mozilla.org/show_bug.cgi?id=2065318) and
[bug 2058247](https://bugzilla.mozilla.org/show_bug.cgi?id=2058247).