Measure Device Counts & Churn

Contact Information

• Contact:
  • troywang@google.com
• Escalation:
  • chromeos-data-eng@google.com
• File a bug: template

Summary

We use a privacy compliant mechanism (private set membership) to measure device counts and device churn.

The client deterministically generates a pseudonymous id using a high entropy seed, which is used to send the pseudo-id at most once from the device.

In the future, there are plans to measure user level metrics.

Developer Notes

active_ts_ field - PLEASE NOTE DETAILS

Please note, we represent the device's online timestamp, adjusted to Pacific Time (PST) in the variable |active_ts_|, which is a part of the UseCaseParameters object.

• Type: base::Time
• Initialization: Adjusted during initialization to Pacific time, based on Daylight savings.
• Usage: Propagated across child classes use cases (1DA, 28DA, Churn, etc.). base::Time methods will be PST-disguised-as-UTC-things (UTCExplode, UTCMidnight calls).

Purpose

• Compare dates in the Pacific Time zone to determine whether device pinged already.
• Determine new PST days.
• Store data in local and preserved file caches.
• Provides PST based metadata in network requests to Fresnel server, such as online PST day.