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// Copyright 2017 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_VARIATIONS_SERVICE_SAFE_SEED_MANAGER_H_
#define COMPONENTS_VARIATIONS_SERVICE_SAFE_SEED_MANAGER_H_
#include "base/memory/raw_ptr.h"
#include "base/time/time.h"
class PrefRegistrySimple;
class PrefService;
namespace variations {
struct ClientFilterableState;
class VariationsSeedStore;
enum class SeedType {
kRegularSeed,
kSafeSeed,
kNullSeed,
};
// As of January 2018, users at the 99.5th percentile, across all platforms,
// tend to experience fewer than 3 consecutive crashes: [1], [2], [3], [4].
// Note, however, that this is less true for the less-stable channels on some
// platforms.
// [1] All platforms, stable channel (consistently stable):
// https://uma.googleplex.com/timeline_v2?sid=90ac80f4573249fb341a8e49501bfcfd
// [2] Most platforms, all channels (consistently stable other than occasional
// spikes on Canary):
// https://uma.googleplex.com/timeline_v2?sid=7af5ba1969db76689a401f982a1db539
// [3] A less stable platform, all channels:
// https://uma.googleplex.com/timeline_v2?sid=07dbc8e4fa9f08e332fb609309a21882
// [4] Another less stable platform, all channels:
// https://uma.googleplex.com/timeline_v2?sid=a7b529ef5d52863fae2d216e963c4cbc
// Overall, the only {platform, channel} combinations that spike above 3
// consecutive crashes are ones with very few users, plus Canary. It's probably
// not realistic to avoid false positives for these less-stable configurations.
constexpr int kCrashStreakSafeSeedThreshold = 3;
constexpr int kCrashStreakNullSeedThreshold = 4;
// The primary class that encapsulates state for managing the safe seed.
class SafeSeedManager {
public:
// Creates a SafeSeedManager instance and updates a safe mode pref,
// kVariationsFailedToFetchSeedStreak, for bookkeeping.
explicit SafeSeedManager(PrefService* local_state);
SafeSeedManager(const SafeSeedManager&) = delete;
SafeSeedManager& operator=(const SafeSeedManager&) = delete;
virtual ~SafeSeedManager();
// Registers safe mode prefs in Local State.
static void RegisterPrefs(PrefRegistrySimple* registry);
// Returns the type of seed the client should use. Uses Regular seed by
// default, but will use Safe seed, and Null seed after continual crashes or
// network fetch failures.
//
// Virtual for testing.
virtual SeedType GetSeedType() const;
// Stores the combined server and client state that control the active
// variations state. May be called at most once per Chrome app launch. As an
// optimization, should not be called when running in safe mode.
//
// Virtual for testing.
virtual void SetActiveSeedState(
const std::string& seed_data,
const std::string& base64_seed_signature,
int seed_milestone,
std::unique_ptr<ClientFilterableState> client_filterable_state,
base::Time seed_fetch_time);
// Records that a fetch has started: pessimistically increments the
// corresponding failure streak for safe mode.
void RecordFetchStarted();
// Records a successful fetch: resets the failure streaks for safe mode.
// Writes the currently active seed to the |seed_store| as a safe seed, if
// appropriate.
void RecordSuccessfulFetch(VariationsSeedStore* seed_store);
private:
// The combined server and client state needed to save an active seed as a
// safe seed. Not set when running in safe mode.
struct ActiveSeedState {
ActiveSeedState(
const std::string& seed_data,
const std::string& base64_seed_signature,
int seed_milestone,
std::unique_ptr<ClientFilterableState> client_filterable_state,
base::Time seed_fetch_time);
~ActiveSeedState();
// The serialized variations seed data.
const std::string seed_data;
// The base64-encoded signature for the seed data.
const std::string base64_seed_signature;
// The milestone with which the active seed was fetched.
const int seed_milestone;
// The client state which is used for filtering studies.
const std::unique_ptr<ClientFilterableState> client_filterable_state;
// The latest timestamp at which this seed was fetched. This is always a
// client-side timestamp, never a server-provided timestamp.
const base::Time seed_fetch_time;
};
// Accessor for active_seed_state_.
const std::optional<ActiveSeedState>& GetActiveSeedState() const;
// The pref service used to persist the variations seed. Weak reference; must
// outlive |this| instance.
raw_ptr<PrefService> local_state_;
std::optional<ActiveSeedState> active_seed_state_;
};
} // namespace variations
#endif // COMPONENTS_VARIATIONS_SERVICE_SAFE_SEED_MANAGER_H_
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