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- // Copyright 2013 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/variations_seed_processor.h"
- #include <stddef.h>
- #include <map>
- #include <vector>
- #include "base/command_line.h"
- #include "base/feature_list.h"
- #include "base/metrics/field_trial.h"
- #include "base/metrics/histogram_functions.h"
- #include "base/metrics/histogram_macros.h"
- #include "base/strings/utf_string_conversions.h"
- #include "components/variations/client_filterable_state.h"
- #include "components/variations/processed_study.h"
- #include "components/variations/study_filtering.h"
- #include "components/variations/variations_associated_data.h"
- #include "components/variations/variations_layers.h"
- #include "third_party/abseil-cpp/absl/types/optional.h"
- namespace variations {
- namespace {
- // Associates the variations params of |experiment|, if present.
- void RegisterExperimentParams(const Study& study,
- const Study::Experiment& experiment) {
- std::map<std::string, std::string> params;
- for (int i = 0; i < experiment.param_size(); ++i) {
- if (experiment.param(i).has_name() && experiment.param(i).has_value())
- params[experiment.param(i).name()] = experiment.param(i).value();
- }
- if (!params.empty())
- AssociateVariationParams(study.name(), experiment.name(), params);
- }
- // Returns the IDCollectionKey with which |experiment| should be associated.
- // Returns nullopt when |experiment| doesn't have a Google web or Google web
- // trigger experiment ID.
- absl::optional<IDCollectionKey> GetKeyForWebExperiment(
- const Study::Experiment& experiment) {
- bool has_web_experiment_id = experiment.has_google_web_experiment_id();
- bool has_web_trigger_experiment_id =
- experiment.has_google_web_trigger_experiment_id();
- if (!has_web_experiment_id && !has_web_trigger_experiment_id)
- return absl::nullopt;
- // An experiment cannot have both |google_web_experiment_id| and
- // |google_trigger_web_experiment_id|. This is enforced by the variations
- // server before generating a variations seed.
- DCHECK(!(has_web_experiment_id && has_web_trigger_experiment_id));
- Study::GoogleWebVisibility visibility = experiment.google_web_visibility();
- if (visibility == Study::FIRST_PARTY) {
- return has_web_trigger_experiment_id
- ? GOOGLE_WEB_PROPERTIES_TRIGGER_FIRST_PARTY
- : GOOGLE_WEB_PROPERTIES_FIRST_PARTY;
- }
- return has_web_trigger_experiment_id
- ? GOOGLE_WEB_PROPERTIES_TRIGGER_ANY_CONTEXT
- : GOOGLE_WEB_PROPERTIES_ANY_CONTEXT;
- }
- // If there are VariationIDs associated with |experiment|, register the
- // VariationIDs.
- void RegisterVariationIds(const Study::Experiment& experiment,
- const std::string& trial_name) {
- if (experiment.has_google_app_experiment_id()) {
- const VariationID variation_id =
- static_cast<VariationID>(experiment.google_app_experiment_id());
- AssociateGoogleVariationIDForce(GOOGLE_APP, trial_name, experiment.name(),
- variation_id);
- }
- absl::optional<IDCollectionKey> key = GetKeyForWebExperiment(experiment);
- if (!key.has_value())
- return;
- // An experiment cannot have both |google_web_experiment_id| and
- // |google_trigger_web_experiment_id|. See GetKeyForWebExperiment() for more
- // details.
- const VariationID variation_id =
- experiment.has_google_web_trigger_experiment_id()
- ? static_cast<VariationID>(
- experiment.google_web_trigger_experiment_id())
- : static_cast<VariationID>(experiment.google_web_experiment_id());
- AssociateGoogleVariationIDForce(key.value(), trial_name, experiment.name(),
- variation_id);
- }
- // Executes |callback| on every override defined by |experiment|.
- void ApplyUIStringOverrides(
- const Study::Experiment& experiment,
- const VariationsSeedProcessor::UIStringOverrideCallback& callback) {
- UMA_HISTOGRAM_COUNTS_100("Variations.StringsOverridden",
- experiment.override_ui_string_size());
- for (int i = 0; i < experiment.override_ui_string_size(); ++i) {
- const Study::Experiment::OverrideUIString& override =
- experiment.override_ui_string(i);
- callback.Run(override.name_hash(), base::UTF8ToUTF16(override.value()));
- }
- }
- // Forces the specified |experiment| to be enabled in |study|.
- void ForceExperimentState(
- const Study& study,
- const Study::Experiment& experiment,
- const VariationsSeedProcessor::UIStringOverrideCallback& override_callback,
- base::FieldTrial* trial) {
- RegisterExperimentParams(study, experiment);
- RegisterVariationIds(experiment, study.name());
- if (study.activation_type() == Study::ACTIVATE_ON_STARTUP) {
- // This call must happen after all params have been registered for the
- // trial. Otherwise, since we look up params by trial and group name, the
- // params won't be registered under the correct key.
- trial->group();
- // UI Strings can only be overridden from ACTIVATE_ON_STARTUP experiments.
- ApplyUIStringOverrides(experiment, override_callback);
- }
- }
- // Registers feature overrides for the chosen experiment in the specified study.
- void RegisterFeatureOverrides(const ProcessedStudy& processed_study,
- base::FieldTrial* trial,
- base::FeatureList* feature_list) {
- const std::string& group_name = trial->GetGroupNameWithoutActivation();
- int experiment_index = processed_study.GetExperimentIndexByName(group_name);
- // If the chosen experiment was not found in the study, simply return.
- // Although not normally expected, but could happen in exception cases, see
- // tests: ExpiredStudy_NoDefaultGroup, ExistingFieldTrial_ExpiredByConfig
- if (experiment_index == -1)
- return;
- const Study& study = *processed_study.study();
- const Study::Experiment& experiment = study.experiment(experiment_index);
- // Process all the features to enable.
- int feature_count = experiment.feature_association().enable_feature_size();
- for (int i = 0; i < feature_count; ++i) {
- feature_list->RegisterFieldTrialOverride(
- experiment.feature_association().enable_feature(i),
- base::FeatureList::OVERRIDE_ENABLE_FEATURE, trial);
- }
- // Process all the features to disable.
- feature_count = experiment.feature_association().disable_feature_size();
- for (int i = 0; i < feature_count; ++i) {
- feature_list->RegisterFieldTrialOverride(
- experiment.feature_association().disable_feature(i),
- base::FeatureList::OVERRIDE_DISABLE_FEATURE, trial);
- }
- // Associate features for groups that do not specify them manually (e.g.
- // "Default" group), so that such groups are reported.
- if (!experiment.has_feature_association()) {
- for (const auto& feature_name : processed_study.associated_features()) {
- feature_list->RegisterFieldTrialOverride(
- feature_name, base::FeatureList::OVERRIDE_USE_DEFAULT, trial);
- }
- }
- }
- // Checks if |experiment| is associated with a forcing flag or feature and if it
- // is, returns whether it should be forced enabled based on the |command_line|
- // or |feature_list| state.
- bool ShouldForceExperiment(const Study::Experiment& experiment,
- const base::CommandLine& command_line,
- const base::FeatureList& feature_list) {
- if (experiment.feature_association().has_forcing_feature_on()) {
- return feature_list.IsFeatureOverriddenFromCommandLine(
- experiment.feature_association().forcing_feature_on(),
- base::FeatureList::OVERRIDE_ENABLE_FEATURE);
- }
- if (experiment.feature_association().has_forcing_feature_off()) {
- return feature_list.IsFeatureOverriddenFromCommandLine(
- experiment.feature_association().forcing_feature_off(),
- base::FeatureList::OVERRIDE_DISABLE_FEATURE);
- }
- if (experiment.has_forcing_flag())
- return command_line.HasSwitch(experiment.forcing_flag());
- return false;
- }
- } // namespace
- VariationsSeedProcessor::VariationsSeedProcessor() = default;
- VariationsSeedProcessor::~VariationsSeedProcessor() = default;
- void VariationsSeedProcessor::CreateTrialsFromSeed(
- const VariationsSeed& seed,
- const ClientFilterableState& client_state,
- const UIStringOverrideCallback& override_callback,
- const base::FieldTrial::EntropyProvider* low_entropy_provider,
- base::FeatureList* feature_list) {
- base::UmaHistogramCounts1000("Variations.AppliedSeed.StudyCount",
- seed.study().size());
- std::vector<ProcessedStudy> filtered_studies;
- VariationsLayers layers(seed, low_entropy_provider);
- FilterAndValidateStudies(seed, client_state, layers, &filtered_studies);
- SetSeedVersion(seed.version());
- for (const ProcessedStudy& study : filtered_studies) {
- CreateTrialFromStudy(study, override_callback, low_entropy_provider,
- feature_list);
- }
- }
- // static
- bool VariationsSeedProcessor::ShouldStudyUseLowEntropy(const Study& study) {
- // This should be kept in sync with the server-side layer validation
- // code: https://go/chrome-variations-layer-validation
- for (int i = 0; i < study.experiment_size(); ++i) {
- const Study::Experiment& experiment = study.experiment(i);
- if (experiment.has_google_web_experiment_id() ||
- experiment.has_google_web_trigger_experiment_id() ||
- experiment.has_chrome_sync_experiment_id()) {
- return true;
- }
- }
- return false;
- }
- void VariationsSeedProcessor::CreateTrialFromStudy(
- const ProcessedStudy& processed_study,
- const UIStringOverrideCallback& override_callback,
- const base::FieldTrial::EntropyProvider* low_entropy_provider,
- base::FeatureList* feature_list) {
- const Study& study = *processed_study.study();
- // If the trial already exists, check if the selected group exists in the
- // |processed_study|. If not, there is nothing to do here.
- base::FieldTrial* existing_trial = base::FieldTrialList::Find(study.name());
- if (existing_trial) {
- int experiment_index = processed_study.GetExperimentIndexByName(
- existing_trial->GetGroupNameWithoutActivation());
- if (experiment_index == -1)
- return;
- }
- // Check if any experiments need to be forced due to a command line
- // flag. Force the first experiment with an existing flag.
- base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
- for (int i = 0; i < study.experiment_size(); ++i) {
- const Study::Experiment& experiment = study.experiment(i);
- if (ShouldForceExperiment(experiment, *command_line, *feature_list)) {
- base::FieldTrial* trial = base::FieldTrialList::CreateFieldTrial(
- study.name(), experiment.name());
- // If |trial| is null, then there might already be a trial forced to a
- // different group (e.g. via --force-fieldtrials). Break out of the loop,
- // but don't return, so that variation ids and params for the selected
- // group will still be picked up.
- if (!trial)
- break;
- if (experiment.feature_association().has_forcing_feature_on()) {
- feature_list->AssociateReportingFieldTrial(
- experiment.feature_association().forcing_feature_on(),
- base::FeatureList::OVERRIDE_ENABLE_FEATURE, trial);
- } else if (experiment.feature_association().has_forcing_feature_off()) {
- feature_list->AssociateReportingFieldTrial(
- experiment.feature_association().forcing_feature_off(),
- base::FeatureList::OVERRIDE_DISABLE_FEATURE, trial);
- }
- ForceExperimentState(study, experiment, override_callback, trial);
- return;
- }
- }
- // This study has no randomized experiments and none of its experiments were
- // forced by flags so don't create a field trial.
- if (processed_study.total_probability() <= 0)
- return;
- uint32_t randomization_seed = 0;
- base::FieldTrial::RandomizationType randomization_type =
- base::FieldTrial::SESSION_RANDOMIZED;
- if (study.has_consistency() &&
- study.consistency() == Study_Consistency_PERMANENT &&
- // If all assignments are to a single group, no need to enable one time
- // randomization (which is more expensive to compute), since the result
- // will be the same.
- !processed_study.all_assignments_to_one_group()) {
- randomization_type = base::FieldTrial::ONE_TIME_RANDOMIZED;
- if (study.has_randomization_seed())
- randomization_seed = study.randomization_seed();
- }
- // The trial is created without specifying an expiration date because the
- // expiration check in field_trial.cc is based on the build date. Instead,
- // the expiration check using |reference_date| is done explicitly below.
- scoped_refptr<base::FieldTrial> trial(
- base::FieldTrialList::FactoryGetFieldTrialWithRandomizationSeed(
- study.name(), processed_study.total_probability(),
- processed_study.GetDefaultExperimentName(), randomization_type,
- randomization_seed, nullptr,
- ShouldStudyUseLowEntropy(study) ? low_entropy_provider : nullptr));
- bool has_overrides = false;
- bool enables_or_disables_features = false;
- for (int i = 0; i < study.experiment_size(); ++i) {
- const Study::Experiment& experiment = study.experiment(i);
- RegisterExperimentParams(study, experiment);
- // Groups with forcing flags have probability 0 and will never be selected.
- // Therefore, there's no need to add them to the field trial.
- if (experiment.has_forcing_flag() ||
- experiment.feature_association().has_forcing_feature_on() ||
- experiment.feature_association().has_forcing_feature_off()) {
- continue;
- }
- if (experiment.name() != study.default_experiment_name())
- trial->AppendGroup(experiment.name(), experiment.probability_weight());
- RegisterVariationIds(experiment, study.name());
- has_overrides = has_overrides || experiment.override_ui_string_size() > 0;
- if (experiment.feature_association().enable_feature_size() != 0 ||
- experiment.feature_association().disable_feature_size() != 0) {
- enables_or_disables_features = true;
- }
- }
- trial->SetForced();
- if (processed_study.is_expired())
- trial->Disable();
- if (enables_or_disables_features)
- RegisterFeatureOverrides(processed_study, trial.get(), feature_list);
- if (study.activation_type() == Study::ACTIVATE_ON_STARTUP) {
- // This call must happen after all params have been registered for the
- // trial. Otherwise, since we look up params by trial and group name, the
- // params won't be registered under the correct key.
- const std::string& group_name = trial->group_name();
- // Don't try to apply overrides if none of the experiments in this study had
- // any.
- if (!has_overrides)
- return;
- // UI Strings can only be overridden from ACTIVATE_ON_STARTUP experiments.
- int experiment_index = processed_study.GetExperimentIndexByName(group_name);
- // If the chosen experiment was not found in the study, simply return.
- // Although not normally expected, but could happen in exception cases, see
- // tests: ExpiredStudy_NoDefaultGroup, ExistingFieldTrial_ExpiredByConfig
- if (experiment_index != -1) {
- ApplyUIStringOverrides(study.experiment(experiment_index),
- override_callback);
- }
- }
- }
- } // namespace variations
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