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- // Copyright 2017 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.
- #include "components/variations/service/safe_seed_manager.h"
- #include "base/base_switches.h"
- #include "base/command_line.h"
- #include "base/cxx17_backports.h"
- #include "base/metrics/histogram_functions.h"
- #include "base/metrics/histogram_macros.h"
- #include "components/prefs/pref_registry.h"
- #include "components/prefs/pref_registry_simple.h"
- #include "components/prefs/pref_service.h"
- #include "components/variations/client_filterable_state.h"
- #include "components/variations/pref_names.h"
- #include "components/variations/variations_seed_store.h"
- #include "components/variations/variations_switches.h"
- namespace variations {
- // Consecutive seed fetch failures are, unfortunately, a bit more common. As of
- // January 2018, users at the 99.5th percentile tend to see fewer than 4
- // consecutive fetch failures on mobile platforms; and users at the 99th
- // percentile tend to see fewer than 5 or 6 consecutive failures on desktop
- // platforms. It makes sense that the characteristics differ on mobile
- // vs. desktop platforms, given that the two use different scheduling algorithms
- // for the fetches. Graphs:
- // [1] Android, all channels (consistently connected):
- // https://uma.googleplex.com/timeline_v2?sid=99d1d4c2490c60bcbde7afeb77c12a28
- // [2] High-connectivity platforms, Stable and Beta channel (consistently
- // connected):
- // https://uma.googleplex.com/timeline_v2?sid=2db5b7278dad41cbf349f5f2cb30efd9
- // [3] Other platforms, Stable and Beta channel (slightly less connected):
- // https://uma.googleplex.com/timeline_v2?sid=d4ba2f3751d211898f8e69214147c2ec
- // [4] All platforms, Dev (even less connected):
- // https://uma.googleplex.com/timeline_v2?sid=5740fb22b17faa823822adfd8e00ec1a
- // [5] All platforms, Canary (actually fairly well-connected!):
- // https://uma.googleplex.com/timeline_v2?sid=3e14d3e4887792bb614db9f3f2c1d48c
- // Note the all of the graphs show a spike on a particular day, presumably due
- // to server-side instability. Moreover, the Dev channel on desktop is an
- // outlier – users on the Dev channel can experience just shy of 9 consecutive
- // failures on some platforms.
- // Decision: There is not an obvious threshold that both achieves a low
- // false-positive rate and provides good coverage for true positives. For now,
- // set a threshold that should minimize false-positives.
- // TODO(isherman): Check in with the networking team about their thoughts on how
- // to find a better balance here.
- constexpr int kFetchFailureStreakThreshold = 25;
- SafeSeedManager::SafeSeedManager(PrefService* local_state)
- : local_state_(local_state) {
- int num_failed_fetches =
- local_state_->GetInteger(prefs::kVariationsFailedToFetchSeedStreak);
- base::UmaHistogramSparse("Variations.SafeMode.Streak.FetchFailures",
- base::clamp(num_failed_fetches, 0, 100));
- }
- SafeSeedManager::~SafeSeedManager() = default;
- // static
- void SafeSeedManager::RegisterPrefs(PrefRegistrySimple* registry) {
- // Verify that the crash streak pref has already been registered.
- DCHECK(
- registry->defaults()->GetValue(prefs::kVariationsCrashStreak, nullptr));
- // Registers one of two prefs used for tracking variations-seed-related
- // failures. The other pref, kVariationsCrashStreak, is registered in
- // CleanExitBeacon::RegisterPrefs(). See components/metrics/
- // clean_exit_beacon.cc for more details.
- registry->RegisterIntegerPref(prefs::kVariationsFailedToFetchSeedStreak, 0);
- }
- bool SafeSeedManager::ShouldRunInSafeMode() const {
- // Ignore any number of failures if the --disable-variations-safe-mode flag is
- // set.
- if (base::CommandLine::ForCurrentProcess()->HasSwitch(
- switches::kDisableVariationsSafeMode)) {
- return false;
- }
- int num_crashes = local_state_->GetInteger(prefs::kVariationsCrashStreak);
- int num_failed_fetches =
- local_state_->GetInteger(prefs::kVariationsFailedToFetchSeedStreak);
- return num_crashes >= kCrashStreakThreshold ||
- num_failed_fetches >= kFetchFailureStreakThreshold;
- }
- void SafeSeedManager::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) {
- DCHECK(!has_set_active_seed_state_);
- has_set_active_seed_state_ = true;
- active_seed_state_ = std::make_unique<ActiveSeedState>(
- seed_data, base64_seed_signature, seed_milestone,
- std::move(client_filterable_state), seed_fetch_time);
- }
- void SafeSeedManager::RecordFetchStarted() {
- // Pessimistically assume the fetch will fail. The failure streak will be
- // reset upon success.
- int num_failures_to_fetch =
- local_state_->GetInteger(prefs::kVariationsFailedToFetchSeedStreak);
- local_state_->SetInteger(prefs::kVariationsFailedToFetchSeedStreak,
- num_failures_to_fetch + 1);
- }
- void SafeSeedManager::RecordSuccessfulFetch(VariationsSeedStore* seed_store) {
- // The first time a fetch succeeds for a given run of Chrome, save the active
- // seed+filter configuration as safe. Note that it's sufficient to do this
- // only on the first successful fetch because the active configuration does
- // not change while Chrome is running. Also, note that it's fine to do this
- // even if running in safe mode, as the saved seed in that case will just be
- // the existing safe seed.
- if (active_seed_state_) {
- seed_store->StoreSafeSeed(active_seed_state_->seed_data,
- active_seed_state_->base64_seed_signature,
- active_seed_state_->seed_milestone,
- *active_seed_state_->client_filterable_state,
- active_seed_state_->seed_fetch_time);
- // The active seed state is only needed for the first time this code path is
- // reached, so free up its memory once the data is no longer needed.
- active_seed_state_.reset();
- }
- // Note: It's important to clear the crash streak as well as the fetch
- // failures streak. Crashes that occur after a successful seed fetch do not
- // prevent updating to a new seed, and therefore do not necessitate falling
- // back to a safe seed.
- local_state_->SetInteger(prefs::kVariationsCrashStreak, 0);
- local_state_->SetInteger(prefs::kVariationsFailedToFetchSeedStreak, 0);
- }
- SafeSeedManager::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)
- : seed_data(seed_data),
- base64_seed_signature(base64_seed_signature),
- seed_milestone(seed_milestone),
- client_filterable_state(std::move(client_filterable_state)),
- seed_fetch_time(seed_fetch_time) {}
- SafeSeedManager::ActiveSeedState::~ActiveSeedState() = default;
- } // namespace variations
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