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 <set>
8 #include <utility>
9 #include <vector>
10
11 #include "base/debug/crash_logging.h"
12 #include "base/debug/dump_without_crashing.h"
13 #include "base/feature_list.h"
14 #include "base/metrics/field_trial.h"
15 #include "base/metrics/field_trial_param_associator.h"
16 #include "base/metrics/histogram_functions.h"
17 #include "base/metrics/metrics_hashes.h"
18 #include "base/notreached.h"
19 #include "base/strings/escape.h"
20 #include "base/strings/string_number_conversions.h"
21 #include "base/strings/string_split.h"
22 #include "base/strings/stringprintf.h"
23 #include "base/time/time_delta_from_string.h"
24 #include "third_party/abseil-cpp/absl/types/optional.h"
25
26 namespace base {
27
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)28 void LogInvalidValue(const Feature& feature,
29 const char* type,
30 const std::string& param_name,
31 const std::string& value_as_string,
32 const std::string& default_value_as_string) {
33 UmaHistogramSparse("Variations.FieldTriamParamsLogInvalidValue",
34 static_cast<int>(base::HashFieldTrialName(
35 FeatureList::GetFieldTrial(feature)->trial_name())));
36 // To anyone noticing these crash dumps in the wild, these parameters come
37 // from server-side experiment configuration. If you're seeing an increase it
38 // is likely due to a bad experiment rollout rather than changes in the client
39 // code.
40 SCOPED_CRASH_KEY_STRING32("FieldTrialParams", "feature_name", feature.name);
41 SCOPED_CRASH_KEY_STRING32("FieldTrialParams", "param_name", param_name);
42 SCOPED_CRASH_KEY_STRING32("FieldTrialParams", "value", value_as_string);
43 SCOPED_CRASH_KEY_STRING32("FieldTrialParams", "default",
44 default_value_as_string);
45 LOG(ERROR) << "Failed to parse field trial param " << param_name
46 << " with string value " << value_as_string << " under feature "
47 << feature.name << " into " << type
48 << ". Falling back to default value of "
49 << default_value_as_string;
50 base::debug::DumpWithoutCrashing();
51 }
52
UnescapeValue(const std::string & value)53 std::string UnescapeValue(const std::string& value) {
54 return UnescapeURLComponent(
55 value, UnescapeRule::PATH_SEPARATORS |
56 UnescapeRule::URL_SPECIAL_CHARS_EXCEPT_PATH_SEPARATORS);
57 }
58
AssociateFieldTrialParams(const std::string & trial_name,const std::string & group_name,const FieldTrialParams & params)59 bool AssociateFieldTrialParams(const std::string& trial_name,
60 const std::string& group_name,
61 const FieldTrialParams& params) {
62 return FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
63 trial_name, group_name, params);
64 }
65
AssociateFieldTrialParamsFromString(const std::string & params_string,FieldTrialParamsDecodeStringFunc decode_data_func)66 bool AssociateFieldTrialParamsFromString(
67 const std::string& params_string,
68 FieldTrialParamsDecodeStringFunc decode_data_func) {
69 // Format: Trial1.Group1:k1/v1/k2/v2,Trial2.Group2:k1/v1/k2/v2
70 std::set<std::pair<std::string, std::string>> trial_groups;
71 for (StringPiece experiment_group :
72 SplitStringPiece(params_string, ",", TRIM_WHITESPACE, SPLIT_WANT_ALL)) {
73 std::vector<StringPiece> experiment = SplitStringPiece(
74 experiment_group, ":", TRIM_WHITESPACE, SPLIT_WANT_ALL);
75 if (experiment.size() != 2) {
76 DLOG(ERROR) << "Experiment and params should be separated by ':'";
77 return false;
78 }
79
80 std::vector<std::string> group_parts =
81 SplitString(experiment[0], ".", TRIM_WHITESPACE, SPLIT_WANT_ALL);
82 if (group_parts.size() != 2) {
83 DLOG(ERROR) << "Trial and group name should be separated by '.'";
84 return false;
85 }
86
87 std::vector<std::string> key_values =
88 SplitString(experiment[1], "/", TRIM_WHITESPACE, SPLIT_WANT_ALL);
89 if (key_values.size() % 2 != 0) {
90 DLOG(ERROR) << "Param name and param value should be separated by '/'";
91 return false;
92 }
93 std::string trial = decode_data_func(group_parts[0]);
94 std::string group = decode_data_func(group_parts[1]);
95 auto trial_group = std::make_pair(trial, group);
96 if (trial_groups.find(trial_group) != trial_groups.end()) {
97 DLOG(ERROR) << StringPrintf(
98 "A (trial, group) pair listed more than once. (%s, %s)",
99 trial.c_str(), group.c_str());
100 return false;
101 }
102 trial_groups.insert(trial_group);
103 std::map<std::string, std::string> params;
104 for (size_t i = 0; i < key_values.size(); i += 2) {
105 std::string key = decode_data_func(key_values[i]);
106 std::string value = decode_data_func(key_values[i + 1]);
107 params[key] = value;
108 }
109 bool result = AssociateFieldTrialParams(trial, group, params);
110 if (!result) {
111 DLOG(ERROR) << "Failed to associate field trial params for group \""
112 << group << "\" in trial \"" << trial << "\"";
113 return false;
114 }
115 }
116 return true;
117 }
118
GetFieldTrialParams(const std::string & trial_name,FieldTrialParams * params)119 bool GetFieldTrialParams(const std::string& trial_name,
120 FieldTrialParams* params) {
121 FieldTrial* trial = FieldTrialList::Find(trial_name);
122 return FieldTrialParamAssociator::GetInstance()->GetFieldTrialParams(trial,
123 params);
124 }
125
GetFieldTrialParamsByFeature(const Feature & feature,FieldTrialParams * params)126 bool GetFieldTrialParamsByFeature(const Feature& feature,
127 FieldTrialParams* params) {
128 if (!FeatureList::IsEnabled(feature))
129 return false;
130
131 FieldTrial* trial = FeatureList::GetFieldTrial(feature);
132 return FieldTrialParamAssociator::GetInstance()->GetFieldTrialParams(trial,
133 params);
134 }
135
GetFieldTrialParamValue(const std::string & trial_name,const std::string & param_name)136 std::string GetFieldTrialParamValue(const std::string& trial_name,
137 const std::string& param_name) {
138 FieldTrialParams params;
139 if (GetFieldTrialParams(trial_name, ¶ms)) {
140 auto it = params.find(param_name);
141 if (it != params.end())
142 return it->second;
143 }
144 return std::string();
145 }
146
GetFieldTrialParamValueByFeature(const Feature & feature,const std::string & param_name)147 std::string GetFieldTrialParamValueByFeature(const Feature& feature,
148 const std::string& param_name) {
149 FieldTrialParams params;
150 if (GetFieldTrialParamsByFeature(feature, ¶ms)) {
151 auto it = params.find(param_name);
152 if (it != params.end())
153 return it->second;
154 }
155 return std::string();
156 }
157
GetFieldTrialParamByFeatureAsInt(const Feature & feature,const std::string & param_name,int default_value)158 int GetFieldTrialParamByFeatureAsInt(const Feature& feature,
159 const std::string& param_name,
160 int default_value) {
161 std::string value_as_string =
162 GetFieldTrialParamValueByFeature(feature, param_name);
163 int value_as_int = 0;
164 if (!StringToInt(value_as_string, &value_as_int)) {
165 if (!value_as_string.empty()) {
166 LogInvalidValue(feature, "an int", param_name, value_as_string,
167 base::NumberToString(default_value));
168 }
169 value_as_int = default_value;
170 }
171 return value_as_int;
172 }
173
GetFieldTrialParamByFeatureAsDouble(const Feature & feature,const std::string & param_name,double default_value)174 double GetFieldTrialParamByFeatureAsDouble(const Feature& feature,
175 const std::string& param_name,
176 double default_value) {
177 std::string value_as_string =
178 GetFieldTrialParamValueByFeature(feature, param_name);
179 double value_as_double = 0;
180 if (!StringToDouble(value_as_string, &value_as_double)) {
181 if (!value_as_string.empty()) {
182 LogInvalidValue(feature, "a double", param_name, value_as_string,
183 base::NumberToString(default_value));
184 }
185 value_as_double = default_value;
186 }
187 return value_as_double;
188 }
189
GetFieldTrialParamByFeatureAsBool(const Feature & feature,const std::string & param_name,bool default_value)190 bool GetFieldTrialParamByFeatureAsBool(const Feature& feature,
191 const std::string& param_name,
192 bool default_value) {
193 std::string value_as_string =
194 GetFieldTrialParamValueByFeature(feature, param_name);
195 if (value_as_string == "true")
196 return true;
197 if (value_as_string == "false")
198 return false;
199
200 if (!value_as_string.empty()) {
201 LogInvalidValue(feature, "a bool", param_name, value_as_string,
202 default_value ? "true" : "false");
203 }
204 return default_value;
205 }
206
GetFieldTrialParamByFeatureAsTimeDelta(const Feature & feature,const std::string & param_name,base::TimeDelta default_value)207 base::TimeDelta GetFieldTrialParamByFeatureAsTimeDelta(
208 const Feature& feature,
209 const std::string& param_name,
210 base::TimeDelta default_value) {
211 std::string value_as_string =
212 GetFieldTrialParamValueByFeature(feature, param_name);
213
214 if (value_as_string.empty())
215 return default_value;
216
217 absl::optional<base::TimeDelta> ret = TimeDeltaFromString(value_as_string);
218 if (!ret.has_value()) {
219 LogInvalidValue(feature, "a base::TimeDelta", param_name, value_as_string,
220 base::NumberToString(default_value.InSecondsF()) + " s");
221 return default_value;
222 }
223
224 return ret.value();
225 }
226
Get() const227 std::string FeatureParam<std::string>::Get() const {
228 const std::string value = GetFieldTrialParamValueByFeature(*feature, name);
229 return value.empty() ? default_value : value;
230 }
231
Get() const232 double FeatureParam<double>::Get() const {
233 return GetFieldTrialParamByFeatureAsDouble(*feature, name, default_value);
234 }
235
Get() const236 int FeatureParam<int>::Get() const {
237 return GetFieldTrialParamByFeatureAsInt(*feature, name, default_value);
238 }
239
Get() const240 bool FeatureParam<bool>::Get() const {
241 return GetFieldTrialParamByFeatureAsBool(*feature, name, default_value);
242 }
243
Get() const244 base::TimeDelta FeatureParam<base::TimeDelta>::Get() const {
245 return GetFieldTrialParamByFeatureAsTimeDelta(*feature, name, default_value);
246 }
247
LogInvalidEnumValue(const Feature & feature,const std::string & param_name,const std::string & value_as_string,int default_value_as_int)248 void LogInvalidEnumValue(const Feature& feature,
249 const std::string& param_name,
250 const std::string& value_as_string,
251 int default_value_as_int) {
252 LogInvalidValue(feature, "an enum", param_name, value_as_string,
253 base::NumberToString(default_value_as_int));
254 }
255
256 } // namespace base
257