third_party/metrics_proto/structured_event.proto

// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

syntax = "proto2";

option optimize_for = LITE_RUNTIME;

package metrics;

// One structured metrics event, containing several hashed and unhashed metrics
// related to a single event type, tied to a single pseudonymous user.
//
// Next tag: 4
message StructuredEventProto {
  // A per-profile, per-client, per-event ID that is used only for structured
  // metrics.
  optional fixed64 profile_event_id = 1;

  // The first 8 bytes of the MD5 hash of the event's name as a string. Each
  // name is defined in src/tools/metrics/structured/structured.xml, and this
  // will be the hash of one of those.
  optional fixed64 event_name_hash = 2;

  // All metric values for this event. Each metric has two properties defined in
  // structured.xml that determine what is recorded.
  //
  // 1. Metric name. This is a string, and the first 8 bytes of its MD5 hash is
  //    recorded as name_hash.
  //
  // 2. Kind. Each metric can store two kinds of values.
  //
  //    - int64. The client supplies an int64 value for the metric, and that
  //      value is recorded as-is in value_raw.
  //
  //    - hashed-string. The client supplies an arbitrary string for the metric.
  //      The string itself is not recorded, instead, value_hmac records the
  //      first 8 bytes of:
  //
  //          HMAC_SHA256(concat(string, metric_name), event_key)
  //
  //      The event_key is a per-profile, per-client, per-event secret 32-byte
  //      key used only for signing hashed values for this event. Keys should
  //      never leave the device, and are rotated at most every 90 days.
  message Metric {
    optional fixed64 name_hash = 1;
    oneof value {
      fixed64 value_hmac = 2;
      int64 value_int64 = 3;
    }
  }
  repeated Metric metrics = 3;
}