src/components/variations/variations_seed_simulator.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   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 "components/variations/variations_seed_simulator.h"
   6
   7 #include <map>
   8
   9 #include "base/metrics/field_trial.h"
  10 #include "components/variations/processed_study.h"
  11 #include "components/variations/proto/study.pb.h"
  12 #include "components/variations/study_filtering.h"
  13 #include "components/variations/variations_associated_data.h"
  14
  15 namespace variations {
  16
  17 namespace {
  18
  19 // Fills in |current_state| with the current process' active field trials, as a
  20 // map of trial names to group names.
  21 void GetCurrentTrialState(std::map<std::string, std::string>* current_state) {
  22   base::FieldTrial::ActiveGroups trial_groups;
  23   base::FieldTrialList::GetActiveFieldTrialGroups(&trial_groups);
  24   for (size_t i = 0; i < trial_groups.size(); ++i)
  25     (*current_state)[trial_groups[i].trial_name] = trial_groups[i].group_name;
  26 }
  27
  28 // Simulate group assignment for the specified study with PERMANENT consistency.
  29 // Returns the experiment group that will be selected. Mirrors logic in
  30 // VariationsSeedProcessor::CreateTrialFromStudy().
  31 std::string SimulateGroupAssignment(
  32     const base::FieldTrial::EntropyProvider& entropy_provider,
  33     const ProcessedStudy& processed_study) {
  34   const Study& study = *processed_study.study();
  35   DCHECK_EQ(Study_Consistency_PERMANENT, study.consistency());
  36
  37   const double entropy_value =
  38       entropy_provider.GetEntropyForTrial(study.name(),
  39                                           study.randomization_seed());
  40   scoped_refptr<base::FieldTrial> trial(
  41       base::FieldTrial::CreateSimulatedFieldTrial(
  42           study.name(), processed_study.total_probability(),
  43           study.default_experiment_name(), entropy_value));
  44
  45   for (int i = 0; i < study.experiment_size(); ++i) {
  46     const Study_Experiment& experiment = study.experiment(i);
  47     // TODO(asvitkine): This needs to properly handle the case where a group was
  48     // forced via forcing_flag in the current state, so that it is not treated
  49     // as changed.
  50     if (!experiment.has_forcing_flag() &&
  51         experiment.name() != study.default_experiment_name()) {
  52       trial->AppendGroup(experiment.name(), experiment.probability_weight());
  53     }
  54   }
  55   if (processed_study.is_expired())
  56     trial->Disable();
  57   return trial->group_name();
  58 }
  59
  60 // Finds an experiment in |study| with name |experiment_name| and returns it,
  61 // or NULL if it does not exist.
  62 const Study_Experiment* FindExperiment(const Study& study,
  63                                        const std::string& experiment_name) {
  64   for (int i = 0; i < study.experiment_size(); ++i) {
  65     if (study.experiment(i).name() == experiment_name)
  66       return &study.experiment(i);
  67   }
  68   return NULL;
  69 }
  70
  71 // Checks whether experiment params set for |experiment| on |study| are exactly
  72 // equal to the params registered for the corresponding field trial in the
  73 // current process.
  74 bool VariationParamsAreEqual(const Study& study,
  75                              const Study_Experiment& experiment) {
  76   std::map<std::string, std::string> params;
  77   GetVariationParams(study.name(), &params);
  78
  79   if (static_cast<int>(params.size()) != experiment.param_size())
  80     return false;
  81
  82   for (int i = 0; i < experiment.param_size(); ++i) {
  83     std::map<std::string, std::string>::const_iterator it =
  84         params.find(experiment.param(i).name());
  85     if (it == params.end() || it->second != experiment.param(i).value())
  86       return false;
  87   }
  88
  89   return true;
  90 }
  91
  92 }  // namespace
  93
  94 VariationsSeedSimulator::Result::Result()
  95     : normal_group_change_count(0),
  96       kill_best_effort_group_change_count(0),
  97       kill_critical_group_change_count(0) {
  98 }
  99
 100 VariationsSeedSimulator::Result::~Result() {
 101 }
 102
 103 VariationsSeedSimulator::VariationsSeedSimulator(
 104     const base::FieldTrial::EntropyProvider& entropy_provider)
 105     : entropy_provider_(entropy_provider) {
 106 }
 107
 108 VariationsSeedSimulator::~VariationsSeedSimulator() {
 109 }
 110
 111 VariationsSeedSimulator::Result VariationsSeedSimulator::SimulateSeedStudies(
 112     const VariationsSeed& seed,
 113     const std::string& locale,
 114     const base::Time& reference_date,
 115     const base::Version& version,
 116     Study_Channel channel,
 117     Study_FormFactor form_factor,
 118     const std::string& hardware_class) {
 119   std::vector<ProcessedStudy> filtered_studies;
 120   FilterAndValidateStudies(seed, locale, reference_date, version, channel,
 121                            form_factor, hardware_class, &filtered_studies);
 122
 123   return ComputeDifferences(filtered_studies);
 124 }
 125
 126 VariationsSeedSimulator::Result VariationsSeedSimulator::ComputeDifferences(
 127     const std::vector<ProcessedStudy>& processed_studies) {
 128   std::map<std::string, std::string> current_state;
 129   GetCurrentTrialState(&current_state);
 130
 131   Result result;
 132   for (size_t i = 0; i < processed_studies.size(); ++i) {
 133     const Study& study = *processed_studies[i].study();
 134     std::map<std::string, std::string>::const_iterator it =
 135         current_state.find(study.name());
 136
 137     // Skip studies that aren't activated in the current state.
 138     // TODO(asvitkine): This should be handled more intelligently. There are
 139     // several cases that fall into this category:
 140     //   1) There's an existing field trial with this name but it is not active.
 141     //   2) There's an existing expired field trial with this name, which is
 142     //      also not considered as active.
 143     //   3) This is a new study config that previously didn't exist.
 144     // The above cases should be differentiated and handled explicitly.
 145     if (it == current_state.end())
 146       continue;
 147
 148     // Study exists in the current state, check whether its group will change.
 149     // Note: The logic below does the right thing if study consistency changes,
 150     // as it doesn't rely on the previous study consistency.
 151     const std::string& selected_group = it->second;
 152     ChangeType change_type = NO_CHANGE;
 153     if (study.consistency() == Study_Consistency_PERMANENT) {
 154       change_type = PermanentStudyGroupChanged(processed_studies[i],
 155                                                selected_group);
 156     } else if (study.consistency() == Study_Consistency_SESSION) {
 157       change_type = SessionStudyGroupChanged(processed_studies[i],
 158                                              selected_group);
 159     }
 160
 161     switch (change_type) {
 162       case NO_CHANGE:
 163         break;
 164       case CHANGED:
 165         ++result.normal_group_change_count;
 166         break;
 167       case CHANGED_KILL_BEST_EFFORT:
 168         ++result.kill_best_effort_group_change_count;
 169         break;
 170       case CHANGED_KILL_CRITICAL:
 171         ++result.kill_critical_group_change_count;
 172         break;
 173     }
 174   }
 175
 176   // TODO(asvitkine): Handle removed studies (i.e. studies that existed in the
 177   // old seed, but were removed). This will require tracking the set of studies
 178   // that were created from the original seed.
 179
 180   return result;
 181 }
 182
 183 VariationsSeedSimulator::ChangeType
 184 VariationsSeedSimulator::ConvertExperimentTypeToChangeType(
 185     Study_Experiment_Type type) {
 186   switch (type) {
 187     case Study_Experiment_Type_NORMAL:
 188       return CHANGED;
 189     case Study_Experiment_Type_IGNORE_CHANGE:
 190       return NO_CHANGE;
 191     case Study_Experiment_Type_KILL_BEST_EFFORT:
 192       return CHANGED_KILL_BEST_EFFORT;
 193     case Study_Experiment_Type_KILL_CRITICAL:
 194       return CHANGED_KILL_CRITICAL;
 195   }
 196   return CHANGED;
 197 }
 198
 199 VariationsSeedSimulator::ChangeType
 200 VariationsSeedSimulator::PermanentStudyGroupChanged(
 201     const ProcessedStudy& processed_study,
 202     const std::string& selected_group) {
 203   const Study& study = *processed_study.study();
 204   DCHECK_EQ(Study_Consistency_PERMANENT, study.consistency());
 205
 206   const std::string simulated_group = SimulateGroupAssignment(entropy_provider_,
 207                                                               processed_study);
 208   const Study_Experiment* experiment = FindExperiment(study, selected_group);
 209   if (simulated_group != selected_group) {
 210     if (experiment)
 211       return ConvertExperimentTypeToChangeType(experiment->type());
 212     return CHANGED;
 213   }
 214
 215   // Current group exists in the study - check whether its params changed.
 216   DCHECK(experiment);
 217   if (!VariationParamsAreEqual(study, *experiment))
 218     return ConvertExperimentTypeToChangeType(experiment->type());
 219   return NO_CHANGE;
 220 }
 221
 222 VariationsSeedSimulator::ChangeType
 223 VariationsSeedSimulator::SessionStudyGroupChanged(
 224     const ProcessedStudy& processed_study,
 225     const std::string& selected_group) {
 226   const Study& study = *processed_study.study();
 227   DCHECK_EQ(Study_Consistency_SESSION, study.consistency());
 228
 229   const Study_Experiment* experiment = FindExperiment(study, selected_group);
 230   if (processed_study.is_expired() &&
 231       selected_group != study.default_experiment_name()) {
 232     // An expired study will result in the default group being selected - mark
 233     // it as changed if the current group differs from the default.
 234     if (experiment)
 235       return ConvertExperimentTypeToChangeType(experiment->type());
 236     return CHANGED;
 237   }
 238
 239   if (!experiment)
 240     return CHANGED;
 241   if (experiment->probability_weight() == 0 &&
 242       !experiment->has_forcing_flag()) {
 243     return ConvertExperimentTypeToChangeType(experiment->type());
 244   }
 245
 246   // Current group exists in the study - check whether its params changed.
 247   if (!VariationParamsAreEqual(study, *experiment))
 248     return ConvertExperimentTypeToChangeType(experiment->type());
 249   return NO_CHANGE;
 250 }
 251
 252 }  // namespace variations