48 lines
3.1 KiB
Markdown
48 lines
3.1 KiB
Markdown
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# Metrics Internals Debug Page
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**chrome://metrics-internals** is a debug page that reports the state of various
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metrics systems.
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The page displays logs that have been collected by the UMA metrics service,
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which are eventually sent to Google servers. These logs can be exported, and
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their proto data can later be inspected using a Google-internal tool:
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[go/metrics-internals-inspector](http://go/metrics-internals-inspector).
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On debug builds, the page will show all logs collected since browser startup,
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including logs from previous sessions that were not sent yet. On release builds,
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the page will instead show logs collected since the page was opened. This
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difference is mostly due to memory concerns (on official releases, we don't want
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logs to be lingering in memory since they can be relatively large).
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> Tip: By using the `--export-uma-logs-to-file=FILE_PATH` command line flag, all
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logs collected throughout the Chrome session will be exported to the passed
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`FILE_PATH` on shutdown (the file is created if it does not already exist). For
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release builds, this flag also has the effect of showing all logs collected
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since browser startup on the page.
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> Note: The delay between logs being closed can be [long]. If you are just
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testing to see if a certain metric (e.g., histogram, user action, etc.) is being
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properly sent to Google servers and you want logs to be collected more often,
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you can use the `--metrics-upload-interval=N` command line flag, where `N` is in
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seconds and is at least `20`.
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[long]: https://source.chromium.org/chromium/chromium/src/+/main:components/metrics/net/cellular_logic_helper.cc;l=18,21;drc=8ba1bad80dc22235693a0dd41fe55c0fd2dbdabd
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Unlike other metrics debug pages ([chrome://user-actions], **chrome://ukm**, and
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[chrome://histograms]), this page focuses mainly on what has actually been sent
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to Google servers. For example, it is possible that a user action shown on
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[chrome://user-actions] is never actually sent (e.g., due to being [truncated]
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for bandwidth reasons). Similarly, a source shown on **chrome://ukm** might be
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[dropped] and hence never be sent. Or, a histogram shown on
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[chrome://histograms] would not have been collected under regular circumstances
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(e.g., subprocess histograms, which are normally only collected periodically,
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but are collected [immediately] when loading **chrome://histograms**). In other
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words, this page displays the actual logs that have been created and sent,
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without modifications.
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[chrome://user-actions]: https://chromium.googlesource.com/chromium/src/+/master/tools/metrics/actions/README.md#Testing
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[chrome://histograms]: https://chromium.googlesource.com/chromium/src/+/master/tools/metrics/histograms/README.md#Testing
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[truncated]: https://source.chromium.org/chromium/chromium/src/+/main:components/metrics/metrics_log.cc;l=552;drc=38321ee39cd73ac2d9d4400c56b90613dee5fe29
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[dropped]: https://source.chromium.org/chromium/chromium/src/+/main:components/ukm/ukm_recorder_impl.cc;l=362;drc=38321ee39cd73ac2d9d4400c56b90613dee5fe29
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[immediately]: https://source.chromium.org/chromium/chromium/src/+/main:content/browser/metrics/histograms_internals_ui.cc;l=100;drc=5e521f43547ebdce502a555c5edb3a18f0c87a8a
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