1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
|
// 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.
#include "components/variations/service/safe_seed_manager.h"
#include <algorithm>
#include "base/base_switches.h"
#include "base/command_line.h"
#include "base/logging.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 kFetchFailureStreakSafeSeedThreshold = 25;
constexpr int kFetchFailureStreakNullSeedThreshold = 50;
SafeSeedManager::SafeSeedManager(PrefService* local_state)
: local_state_(local_state) {
int num_failed_fetches =
local_state_->GetInteger(prefs::kVariationsFailedToFetchSeedStreak);
base::UmaHistogramSparse("Variations.SafeMode.Streak.FetchFailures",
std::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);
}
SeedType SafeSeedManager::GetSeedType() const {
// Ignore any number of failures if the --disable-variations-safe-mode flag is
// set.
if (base::CommandLine::ForCurrentProcess()->HasSwitch(
switches::kDisableVariationsSafeMode)) {
return SeedType::kRegularSeed;
}
int num_crashes = local_state_->GetInteger(prefs::kVariationsCrashStreak);
int num_failed_fetches =
local_state_->GetInteger(prefs::kVariationsFailedToFetchSeedStreak);
if (num_crashes >= kCrashStreakNullSeedThreshold ||
num_failed_fetches >= kFetchFailureStreakNullSeedThreshold) {
#if BUILDFLAG(IS_CHROMEOS)
// Logging is useful in listnr reports for ChromeOS (http://b/277650823).
LOG(ERROR) << "Using finch safe mode null seed: num_crashes=" << num_crashes
<< ", num_failed_fetches=" << num_failed_fetches;
#endif // BUILDFLAG(IS_CHROMEOS)
return SeedType::kNullSeed;
}
if (num_crashes >= kCrashStreakSafeSeedThreshold ||
num_failed_fetches >= kFetchFailureStreakSafeSeedThreshold) {
#if BUILDFLAG(IS_CHROMEOS)
LOG(ERROR) << "Using finch safe mode safe seed: num_crashes=" << num_crashes
<< ", num_failed_fetches=" << num_failed_fetches;
#endif // BUILDFLAG(IS_CHROMEOS)
return SeedType::kSafeSeed;
}
return SeedType::kRegularSeed;
}
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.
const std::optional<ActiveSeedState>& active_seed_state =
GetActiveSeedState();
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.
ClearActiveSeedState();
}
// 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);
}
} // namespace variations
|
