Re: [dev-platform] Are we Glean yet? Yes!
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Andrew Overholt
Jul 9, 2025, 7:33:06 PMJul 9
to Florian Quèze, dev-platform, Firefox Dev
2086 probes migrated 😅 Great work!
On Wed, Jul 9, 2025 at 7:18 PM Florian Quèze <flo...@queze.net> wrote:
--tl;dr: All data collection in Firefox Desktop now happens using Glean. Legacy telemetry recording APIs have been removed.
With over 419 patches landed, 593 reviews from 75 unique reviewers (thank you!), 1242 files changed and 2086 probes migrated or removed since we decided to accelerate the migration [1], the effort to migrate data collection in Firefox Desktop from legacy Telemetry to Glean is now completed: arewegleanyet.com reached 100% today!
To avoid causing immediate disruption in existing queries, the data for migrated probes is being sent to both Glean and legacy telemetry through automatic mirroring. We expect this mirroring to last about a year, to allow year-over-year queries and give people time to update their queries.
Legacy telemetry recording APIs have been removed to ensure no new legacy-Telemetry only data collection is introduced, but legacy telemetry testing APIs are still in use. Some existing probes had test coverage and the tests still pass, checking the data recorded through mirroring.
No immediate action is required, but it would be a good idea to start modifying tests using legacy telemetry APIs to instead check the data recorded in Glean[2].
Once the mirroring period is over (exact date TBD), legacy telemetry will stop sending data, and the remaining legacy telemetry code will be dead code to clean-up. If you already know you don’t need to have your data in both legacy telemetry and Glean, to reduce costs please remove the legacy telemetry mirrors for glean metrics in your code by removing the telemetry_mirror property from the Glean metrics, and removing the named definitions from Histograms.json, Scalars.yaml, or Events.yaml.
Need help? Ask in https://chat.mozilla.org/#/room/#telemetry:mozilla.org
[1] https://docs.google.com/document/d/14xYKOOi-8dHKcCP1awcT4_LxxyNFTB6Tkv18zQUGhn4/edit
[2]: https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/instrumentation_tests.html
--Florian Quèze
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Bobby Holley
Jul 9, 2025, 8:27:08 PMJul 9
to Andrew Overholt, Florian Quèze, dev-platform, Firefox Dev
Amazing work. Thank you Florian for relentlessly driving this to the finish line, and thanks to everyone who pitched in to get us there.
Nick Alexander
Jul 9, 2025, 9:51:26 PMJul 9
to Florian Quèze, dev-platform, Firefox Dev
On Wed, Jul 9, 2025 at 4:18 PM Florian Quèze <flo...@queze.net> wrote:
tl;dr: All data collection in Firefox Desktop now happens using Glean. Legacy telemetry recording APIs have been removed.
With over 419 patches landed, 593 reviews from 75 unique reviewers (thank you!), 1242 files changed and 2086 probes migrated or removed since we decided to accelerate the migration [1], the effort to migrate data collection in Firefox Desktop from legacy Telemetry to Glean is now completed: arewegleanyet.com reached 100% today!
The amount of time, effort, and tenacity this project required was very high. Thanks and congratulations to Florian and Chris Hutten-Czapski for making this happen! And thanks to Firefox technical leadership for prioritizing this "last mile" effort, which too often languishes in favour of more immediate priorities.
Well done!
Nick
Mike Conley
Jul 10, 2025, 11:44:36 AMJul 10
to Nick Alexander, Florian Quèze, dev-platform, Firefox Dev
Yep, big lift and great job. Wonderful work Florian, and everybody who helped drive this through!
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Florian Quèze
Jul 11, 2025, 9:28:21 AMJul 11
to dev-platform, Firefox Dev
tl;dr: All data collection in Firefox Desktop now happens using Glean. Legacy telemetry recording APIs have been removed.
With over 419 patches landed, 593 reviews from 75 unique reviewers (thank you!), 1242 files changed and 2086 probes migrated or removed since we decided to accelerate the migration [1], the effort to migrate data collection in Firefox Desktop from legacy Telemetry to Glean is now completed: arewegleanyet.com reached 100% today!
With over 419 patches landed, 593 reviews from 75 unique reviewers (thank you!), 1242 files changed and 2086 probes migrated or removed since we decided to accelerate the migration [1], the effort to migrate data collection in Firefox Desktop from legacy Telemetry to Glean is now completed: arewegleanyet.com reached 100% today!
To avoid causing immediate disruption in existing queries, the data for migrated probes is being sent to both Glean and legacy telemetry through automatic mirroring. We expect this mirroring to last about a year, to allow year-over-year queries and give people time to update their queries.
Legacy telemetry recording APIs have been removed to ensure no new legacy-Telemetry only data collection is introduced, but legacy telemetry testing APIs are still in use. Some existing probes had test coverage and the tests still pass, checking the data recorded through mirroring.
No immediate action is required, but it would be a good idea to start modifying tests using legacy telemetry APIs to instead check the data recorded in Glean[2].
Once the mirroring period is over (exact date TBD), legacy telemetry will stop sending data, and the remaining legacy telemetry code will be dead code to clean-up. If you already know you don’t need to have your data in both legacy telemetry and Glean, to reduce costs please remove the legacy telemetry mirrors for glean metrics in your code by removing the telemetry_mirror property from the Glean metrics, and removing the named definitions from Histograms.json, Scalars.yaml, or Events.yaml.
Need help? Ask in https://chat.mozilla.org/#/room/#telemetry:mozilla.org
[1] https://docs.google.com/document/d/14xYKOOi-8dHKcCP1awcT4_LxxyNFTB6Tkv18zQUGhn4/edit
[2]: https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/instrumentation_tests.html
Legacy telemetry recording APIs have been removed to ensure no new legacy-Telemetry only data collection is introduced, but legacy telemetry testing APIs are still in use. Some existing probes had test coverage and the tests still pass, checking the data recorded through mirroring.
No immediate action is required, but it would be a good idea to start modifying tests using legacy telemetry APIs to instead check the data recorded in Glean[2].
Once the mirroring period is over (exact date TBD), legacy telemetry will stop sending data, and the remaining legacy telemetry code will be dead code to clean-up. If you already know you don’t need to have your data in both legacy telemetry and Glean, to reduce costs please remove the legacy telemetry mirrors for glean metrics in your code by removing the telemetry_mirror property from the Glean metrics, and removing the named definitions from Histograms.json, Scalars.yaml, or Events.yaml.
Need help? Ask in https://chat.mozilla.org/#/room/#telemetry:mozilla.org
[1] https://docs.google.com/document/d/14xYKOOi-8dHKcCP1awcT4_LxxyNFTB6Tkv18zQUGhn4/edit
[2]: https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/instrumentation_tests.html
--
Florian Quèze
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