chromium/components/metrics/structured/lib/key_data.h

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

#ifndef COMPONENTS_METRICS_STRUCTURED_LIB_KEY_DATA_H_
#define COMPONENTS_METRICS_STRUCTURED_LIB_KEY_DATA_H_

#include <memory>
#include <optional>
#include <string>
#include <string_view>

#include "base/memory/scoped_refptr.h"
#include "base/memory/weak_ptr.h"
#include "base/sequence_checker.h"
#include "base/task/sequenced_task_runner.h"
#include "base/time/time.h"
#include "components/metrics/structured/lib/persistent_proto.h"
#include "components/metrics/structured/lib/proto/key.pb.h"

namespace metrics::structured {

// KeyData is the central class for managing keys and generating hashes for
// structured metrics.
//
// The class maintains one key and its rotation data for every project defined
// in /tools/metrics/structured/sync/structured.xml. This can be used to
// generate:
//  - an ID for the project with KeyData::Id.
//  - a hash of a given value for an event with KeyData::HmacMetric.
//
// Every project has a uint64_t project_name_hash that is generated by taking
// the first 8 bytes of MD5 hash of the project name. Keys for the project are
// retrieved using this project_name_hash. For more details, refer to
// //tools/metrics/structured/ccodegen.py.
//
// KeyData performs key rotation. Every project is associated with a rotation
// period, which is 90 days unless specified in structured.xml. Keys are rotated
// with a resolution of one day. They are guaranteed not to be used for
// HmacMetric or UserProjectId for longer than their rotation period, except in
// cases of local clock changes.
//
// When first created, every project's key rotation date is selected uniformly
// so that there is an even distribution of rotations across users. This means
// that, for most users, the first rotation period will be shorter than the
// standard full rotation period for that project.
class KeyData { … };

}  // namespace metrics::structured

#endif  // COMPONENTS_METRICS_STRUCTURED_LIB_KEY_DATA_H_