add Garmin Connect exporter

[barnes-c]

Hi @RichiH & @juliusv,
I have a exporter which I would like to share with people who are interested in their health data from Garmin.
Hope you dont mind the ping as stated in your CONTRIBUTING.md.

Best regards,
Chris

Some example metrics of the exporter:

curl -s localhost:10043/metrics | grep ^garmin_ | head -60
garmin_activity_calories_total{type="cycling"} 342
garmin_activity_calories_total{type="hiking"} 2402
garmin_activity_calories_total{type="kayaking_v2"} 1292
garmin_activity_calories_total{type="lap_swimming"} 1009
garmin_activity_calories_total{type="resort_skiing"} 11311
garmin_activity_calories_total{type="running"} 4754
garmin_activity_calories_total{type="yoga"} 212
garmin_activity_count{type="cycling"} 1
garmin_activity_count{type="hiking"} 3
garmin_activity_count{type="kayaking_v2"} 2
garmin_activity_count{type="lap_swimming"} 3
garmin_activity_count{type="resort_skiing"} 7
garmin_activity_count{type="running"} 11
garmin_activity_count{type="yoga"} 3
garmin_activity_distance_meters_total{type="cycling"} 10652.8095703125
garmin_activity_distance_meters_total{type="hiking"} 19863.919921875
garmin_activity_distance_meters_total{type="kayaking_v2"} 16700.5400390625
garmin_activity_distance_meters_total{type="lap_swimming"} 4225
garmin_activity_distance_meters_total{type="resort_skiing"} 500387.22265625
garmin_activity_distance_meters_total{type="running"} 64118.269775390625
garmin_activity_distance_meters_total{type="yoga"} 0
garmin_activity_duration_seconds_total{type="cycling"} 4539.14599609375
garmin_activity_duration_seconds_total{type="hiking"} 26278.85791015625
garmin_activity_duration_seconds_total{type="kayaking_v2"} 15533.6337890625
garmin_activity_duration_seconds_total{type="lap_swimming"} 5458.0679931640625
garmin_activity_duration_seconds_total{type="resort_skiing"} 136557.6103515625
garmin_activity_duration_seconds_total{type="running"} 21620.8759765625
garmin_activity_duration_seconds_total{type="yoga"} 3022.873992919922
garmin_activity_last_timestamp_seconds{type="cycling"} 1.775749283e+09
garmin_activity_last_timestamp_seconds{type="hiking"} 1.779010913e+09
garmin_activity_last_timestamp_seconds{type="kayaking_v2"} 1.777894296e+09
garmin_activity_last_timestamp_seconds{type="lap_swimming"} 1.768409449e+09
garmin_activity_last_timestamp_seconds{type="resort_skiing"} 1.774689115e+09
garmin_activity_last_timestamp_seconds{type="running"} 1.778605586e+09
garmin_activity_last_timestamp_seconds{type="yoga"} 1.776274432e+09
garmin_activity_lifetime_count 304
garmin_body_composition_weight_grams_avg 76249.5
garmin_device_count 1
garmin_device_info{device_id="XXX",name="Forerunner 965",status="active",type="Forerunner 965"} 1
garmin_exporter_build_info{branch="",goarch="arm64",goos="darwin",goversion="go1.26.3",revision="dffc6b983076a17c6da844b81d8e0061d8309e2f-modified",tags="unknown",version=""} 1
garmin_goals_active_total 0
garmin_goals_earned_badges_total 50
garmin_heartrate_max_bpm 144
garmin_heartrate_min_bpm 42
garmin_heartrate_resting_bpm 46
garmin_heartrate_seven_day_avg_resting_bpm 50
garmin_hydration_goal_ml 3000
garmin_hydration_intake_ml 0
garmin_intensity_moderate_minutes_total 0
garmin_intensity_vigorous_minutes_total 0
garmin_intensity_weekly_goal_minutes 0
garmin_respiration_avg_waking_bpm 14
garmin_respiration_highest_bpm 22
garmin_respiration_lowest_bpm 9
garmin_scrape_collector_duration_seconds{collector="activities"} 0.401578625
garmin_scrape_collector_duration_seconds{collector="bloodpressure"} 0.410024125
garmin_scrape_collector_duration_seconds{collector="body"} 0.421912375
garmin_scrape_collector_duration_seconds{collector="bodycomposition"} 0.212123834
garmin_scrape_collector_duration_seconds{collector="cycling"} 0.208700833
garmin_scrape_collector_duration_seconds{collector="devices"} 0.438616958

[bwplotka]

Hello from the bug scrub!

This is great, we don't have a great official policy of what should go in, but it looks good (e.g. license) and @ArthurSens wanted to try it before merging.

From my POV it looks like a great addition!

Thanks!

[ArthurSens]

Hey @barnes-c, I'm a huge fan of Garmin, and knowing that you've built an exporter for it is awesome news! I, too, have hacked around with the Garmin Connect app, and some past experience makes me a bit concerned.

Garmin has an official Developers Program, which requires developers to formally apply for and obtain an API key to integrate with apps that require API access. The "unofficial" way is the way you, myself, and several other people have done, which is to authenticate through the Garmin Connect app, and use the internal endpoints that the Mobile App uses. Garmin changes those internal API a lot, which means the Garmin exporter needs to constantly be re-built to keep in sync with Garmin Connect internal APIs.

A Garmin exporter is awesome, and I'll be a happy user, but I'm wondering how you plan to keep it up to date in the long run. It would be a shame to advertise an exporter that doesn't work in a few months 😅

[barnes-c]

Hi @ArthurSens,
thanks on your interest :)

Garmin changes those internal API a lot, which means the Garmin exporter needs to constantly be re-built to keep in sync with Garmin Connect internal APIs

Yes, I know. I contributed to garth where we already had that problem. Usually this only happens once a year but now with the bigger changes in March garth was deprecated which is why I also build a go-garminconnect client so I dont need to depend on 3rd party libs and own the auth impl

I'm wondering how you plan to keep it up to date in the long run

Im very interested in keeping it running because with this I get to combine work + hobbies. Im a trainer of a local cycling team and use this exporter atm to track my athletes data. TLDR it helps me at my hobbies/job

Hope that answers your questions :)

[ArthurSens]

Thanks for the answers, I'm happy to merge now that you've shared some past experience.

I got it running without problems as well :)