1 // Copyright 2017 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "base/metrics/field_trial_params.h"
6
7 #include <optional>
8 #include <set>
9 #include <string_view>
10 #include <utility>
11 #include <vector>
12
13 #include "base/debug/crash_logging.h"
14 #include "base/debug/dump_without_crashing.h"
15 #include "base/feature_list.h"
16 #include "base/metrics/field_trial.h"
17 #include "base/metrics/field_trial_param_associator.h"
18 #include "base/metrics/histogram_functions.h"
19 #include "base/metrics/metrics_hashes.h"
20 #include "base/notreached.h"
21 #include "base/strings/escape.h"
22 #include "base/strings/string_number_conversions.h"
23 #include "base/strings/string_split.h"
24 #include "base/strings/stringprintf.h"
25 #include "base/time/time_delta_from_string.h"
26
27 namespace base {
28
LogInvalidValue(const Feature & feature,const char * type,const std::string & param_name,const std::string & value_as_string,const std::string & default_value_as_string)29 void LogInvalidValue(const Feature& feature,
30 const char* type,
31 const std::string& param_name,
32 const std::string& value_as_string,
33 const std::string& default_value_as_string) {
34 UmaHistogramSparse("Variations.FieldTriamParamsLogInvalidValue",
35 static_cast<int>(base::HashFieldTrialName(
36 FeatureList::GetFieldTrial(feature)->trial_name())));
37 // To anyone noticing these crash dumps in the wild, these parameters come
38 // from server-side experiment configuration. If you're seeing an increase it
39 // is likely due to a bad experiment rollout rather than changes in the client
40 // code.
41 SCOPED_CRASH_KEY_STRING32("FieldTrialParams", "feature_name", feature.name);
42 SCOPED_CRASH_KEY_STRING32("FieldTrialParams", "param_name", param_name);
43 SCOPED_CRASH_KEY_STRING32("FieldTrialParams", "value", value_as_string);
44 SCOPED_CRASH_KEY_STRING32("FieldTrialParams", "default",
45 default_value_as_string);
46 LOG(ERROR) << "Failed to parse field trial param " << param_name
47 << " with string value " << value_as_string << " under feature "
48 << feature.name << " into " << type
49 << ". Falling back to default value of "
50 << default_value_as_string;
51 base::debug::DumpWithoutCrashing();
52 }
53
UnescapeValue(const std::string & value)54 std::string UnescapeValue(const std::string& value) {
55 return UnescapeURLComponent(
56 value, UnescapeRule::PATH_SEPARATORS |
57 UnescapeRule::URL_SPECIAL_CHARS_EXCEPT_PATH_SEPARATORS);
58 }
59
AssociateFieldTrialParams(const std::string & trial_name,const std::string & group_name,const FieldTrialParams & params)60 bool AssociateFieldTrialParams(const std::string& trial_name,
61 const std::string& group_name,
62 const FieldTrialParams& params) {
63 return FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
64 trial_name, group_name, params);
65 }
66
AssociateFieldTrialParamsFromString(const std::string & params_string,FieldTrialParamsDecodeStringFunc decode_data_func)67 bool AssociateFieldTrialParamsFromString(
68 const std::string& params_string,
69 FieldTrialParamsDecodeStringFunc decode_data_func) {
70 // Format: Trial1.Group1:k1/v1/k2/v2,Trial2.Group2:k1/v1/k2/v2
71 std::set<std::pair<std::string, std::string>> trial_groups;
72 for (std::string_view experiment_group :
73 SplitStringPiece(params_string, ",", TRIM_WHITESPACE, SPLIT_WANT_ALL)) {
74 std::vector<std::string_view> experiment = SplitStringPiece(
75 experiment_group, ":", TRIM_WHITESPACE, SPLIT_WANT_ALL);
76 if (experiment.size() != 2) {
77 DLOG(ERROR) << "Experiment and params should be separated by ':'";
78 return false;
79 }
80
81 std::vector<std::string> group_parts =
82 SplitString(experiment[0], ".", TRIM_WHITESPACE, SPLIT_WANT_ALL);
83 if (group_parts.size() != 2) {
84 DLOG(ERROR) << "Trial and group name should be separated by '.'";
85 return false;
86 }
87
88 std::vector<std::string> key_values =
89 SplitString(experiment[1], "/", TRIM_WHITESPACE, SPLIT_WANT_ALL);
90 if (key_values.size() % 2 != 0) {
91 DLOG(ERROR) << "Param name and param value should be separated by '/'";
92 return false;
93 }
94 std::string trial = decode_data_func(group_parts[0]);
95 std::string group = decode_data_func(group_parts[1]);
96 auto trial_group = std::make_pair(trial, group);
97 if (trial_groups.find(trial_group) != trial_groups.end()) {
98 DLOG(ERROR) << StringPrintf(
99 "A (trial, group) pair listed more than once. (%s, %s)",
100 trial.c_str(), group.c_str());
101 return false;
102 }
103 trial_groups.insert(trial_group);
104 std::map<std::string, std::string> params;
105 for (size_t i = 0; i < key_values.size(); i += 2) {
106 std::string key = decode_data_func(key_values[i]);
107 std::string value = decode_data_func(key_values[i + 1]);
108 params[key] = value;
109 }
110 bool result = AssociateFieldTrialParams(trial, group, params);
111 if (!result) {
112 DLOG(ERROR) << "Failed to associate field trial params for group \""
113 << group << "\" in trial \"" << trial << "\"";
114 return false;
115 }
116 }
117 return true;
118 }
119
GetFieldTrialParams(const std::string & trial_name,FieldTrialParams * params)120 bool GetFieldTrialParams(const std::string& trial_name,
121 FieldTrialParams* params) {
122 FieldTrial* trial = FieldTrialList::Find(trial_name);
123 return FieldTrialParamAssociator::GetInstance()->GetFieldTrialParams(trial,
124 params);
125 }
126
GetFieldTrialParamsByFeature(const Feature & feature,FieldTrialParams * params)127 bool GetFieldTrialParamsByFeature(const Feature& feature,
128 FieldTrialParams* params) {
129 if (!FeatureList::IsEnabled(feature))
130 return false;
131
132 FieldTrial* trial = FeatureList::GetFieldTrial(feature);
133 return FieldTrialParamAssociator::GetInstance()->GetFieldTrialParams(trial,
134 params);
135 }
136
GetFieldTrialParamValue(const std::string & trial_name,const std::string & param_name)137 std::string GetFieldTrialParamValue(const std::string& trial_name,
138 const std::string& param_name) {
139 FieldTrialParams params;
140 if (GetFieldTrialParams(trial_name, ¶ms)) {
141 auto it = params.find(param_name);
142 if (it != params.end())
143 return it->second;
144 }
145 return std::string();
146 }
147
GetFieldTrialParamValueByFeature(const Feature & feature,const std::string & param_name)148 std::string GetFieldTrialParamValueByFeature(const Feature& feature,
149 const std::string& param_name) {
150 FieldTrialParams params;
151 if (GetFieldTrialParamsByFeature(feature, ¶ms)) {
152 auto it = params.find(param_name);
153 if (it != params.end())
154 return it->second;
155 }
156 return std::string();
157 }
158
GetFieldTrialParamByFeatureAsInt(const Feature & feature,const std::string & param_name,int default_value)159 int GetFieldTrialParamByFeatureAsInt(const Feature& feature,
160 const std::string& param_name,
161 int default_value) {
162 std::string value_as_string =
163 GetFieldTrialParamValueByFeature(feature, param_name);
164 int value_as_int = 0;
165 if (!StringToInt(value_as_string, &value_as_int)) {
166 if (!value_as_string.empty()) {
167 LogInvalidValue(feature, "an int", param_name, value_as_string,
168 base::NumberToString(default_value));
169 }
170 value_as_int = default_value;
171 }
172 return value_as_int;
173 }
174
GetFieldTrialParamByFeatureAsDouble(const Feature & feature,const std::string & param_name,double default_value)175 double GetFieldTrialParamByFeatureAsDouble(const Feature& feature,
176 const std::string& param_name,
177 double default_value) {
178 std::string value_as_string =
179 GetFieldTrialParamValueByFeature(feature, param_name);
180 double value_as_double = 0;
181 if (!StringToDouble(value_as_string, &value_as_double)) {
182 if (!value_as_string.empty()) {
183 LogInvalidValue(feature, "a double", param_name, value_as_string,
184 base::NumberToString(default_value));
185 }
186 value_as_double = default_value;
187 }
188 return value_as_double;
189 }
190
GetFieldTrialParamByFeatureAsBool(const Feature & feature,const std::string & param_name,bool default_value)191 bool GetFieldTrialParamByFeatureAsBool(const Feature& feature,
192 const std::string& param_name,
193 bool default_value) {
194 std::string value_as_string =
195 GetFieldTrialParamValueByFeature(feature, param_name);
196 if (value_as_string == "true")
197 return true;
198 if (value_as_string == "false")
199 return false;
200
201 if (!value_as_string.empty()) {
202 LogInvalidValue(feature, "a bool", param_name, value_as_string,
203 default_value ? "true" : "false");
204 }
205 return default_value;
206 }
207
GetFieldTrialParamByFeatureAsTimeDelta(const Feature & feature,const std::string & param_name,base::TimeDelta default_value)208 base::TimeDelta GetFieldTrialParamByFeatureAsTimeDelta(
209 const Feature& feature,
210 const std::string& param_name,
211 base::TimeDelta default_value) {
212 std::string value_as_string =
213 GetFieldTrialParamValueByFeature(feature, param_name);
214
215 if (value_as_string.empty())
216 return default_value;
217
218 std::optional<base::TimeDelta> ret = TimeDeltaFromString(value_as_string);
219 if (!ret.has_value()) {
220 LogInvalidValue(feature, "a base::TimeDelta", param_name, value_as_string,
221 base::NumberToString(default_value.InSecondsF()) + " s");
222 return default_value;
223 }
224
225 return ret.value();
226 }
227
Get() const228 std::string FeatureParam<std::string>::Get() const {
229 // We don't use `GetFieldTrialParamValueByFeature()` to handle empty values in
230 // the map.
231 FieldTrialParams params;
232 if (GetFieldTrialParamsByFeature(*feature, ¶ms)) {
233 auto it = params.find(name);
234 if (it != params.end()) {
235 return it->second;
236 }
237 }
238 return default_value;
239 }
240
Get() const241 double FeatureParam<double>::Get() const {
242 return GetFieldTrialParamByFeatureAsDouble(*feature, name, default_value);
243 }
244
Get() const245 int FeatureParam<int>::Get() const {
246 return GetFieldTrialParamByFeatureAsInt(*feature, name, default_value);
247 }
248
Get() const249 bool FeatureParam<bool>::Get() const {
250 return GetFieldTrialParamByFeatureAsBool(*feature, name, default_value);
251 }
252
Get() const253 base::TimeDelta FeatureParam<base::TimeDelta>::Get() const {
254 return GetFieldTrialParamByFeatureAsTimeDelta(*feature, name, default_value);
255 }
256
LogInvalidEnumValue(const Feature & feature,const std::string & param_name,const std::string & value_as_string,int default_value_as_int)257 void LogInvalidEnumValue(const Feature& feature,
258 const std::string& param_name,
259 const std::string& value_as_string,
260 int default_value_as_int) {
261 LogInvalidValue(feature, "an enum", param_name, value_as_string,
262 base::NumberToString(default_value_as_int));
263 }
264
265 } // namespace base
266