components/variations/variations_seed_simulator.h

   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 #ifndef COMPONENTS_VARIATIONS_VARIATIONS_SEED_SIMULATOR_H_
   6 #define COMPONENTS_VARIATIONS_VARIATIONS_SEED_SIMULATOR_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/compiler_specific.h"
  12 #include "base/gtest_prod_util.h"
  13 #include "base/metrics/field_trial.h"
  14 #include "base/version.h"
  15 #include "components/variations/proto/study.pb.h"
  16 #include "components/variations/proto/variations_seed.pb.h"
  17
  18 namespace variations {
  19
  20 class ProcessedStudy;
  21 class VariationsSeed;
  22
  23 // VariationsSeedSimulator simulates the result of creating a set of studies
  24 // and detecting which studies would result in group changes.
  25 class VariationsSeedSimulator {
  26  public:
  27   // The result of variations seed simulation, counting the number of experiment
  28   // group changes of each type that are expected to occur on a restart with the
  29   // seed.
  30   struct Result {
  31     // The number of expected group changes that do not fall into any special
  32     // category. This is a lower bound due to session randomized studies.
  33     int normal_group_change_count;
  34
  35     // The number of expected group changes that fall in the category of killed
  36     // experiments that should trigger the "best effort" restart mechanism.
  37     int kill_best_effort_group_change_count;
  38
  39     // The number of expected group changes that fall in the category of killed
  40     // experiments that should trigger the "critical" restart mechanism.
  41     int kill_critical_group_change_count;
  42
  43     Result();
  44     ~Result();
  45   };
  46
  47   // Creates the simulator with the given entropy |provider|.
  48   explicit VariationsSeedSimulator(
  49       const base::FieldTrial::EntropyProvider& provider);
  50   virtual ~VariationsSeedSimulator();
  51
  52   // Computes differences between the current process' field trial state and
  53   // the result of evaluating |seed| with the given parameters. Returns the
  54   // results of the simulation as a set of expected group change counts of each
  55   // type.
  56   Result SimulateSeedStudies(const VariationsSeed& seed,
  57                              const std::string& locale,
  58                              const base::Time& reference_date,
  59                              const base::Version& version,
  60                              Study_Channel channel,
  61                              Study_FormFactor form_factor,
  62                              const std::string& hardware_class);
  63
  64  private:
  65   friend class VariationsSeedSimulatorTest;
  66
  67   enum ChangeType {
  68     NO_CHANGE,
  69     CHANGED,
  70     CHANGED_KILL_BEST_EFFORT,
  71     CHANGED_KILL_CRITICAL,
  72   };
  73
  74   // Computes differences between the current process' field trial state and
  75   // the result of evaluating the |processed_studies| list. It is expected that
  76   // |processed_studies| have already been filtered and only contain studies
  77   // that apply to the configuration being simulated. Returns the results of the
  78   // simulation as a set of expected group change counts of each type.
  79   Result ComputeDifferences(
  80       const std::vector<ProcessedStudy>& processed_studies);
  81
  82   // Maps proto enum |type| to a ChangeType.
  83   ChangeType ConvertExperimentTypeToChangeType(Study_Experiment_Type type);
  84
  85   // For the given |processed_study| with PERMANENT consistency, simulates group
  86   // assignment and returns a corresponding ChangeType if the result differs
  87   // from that study's group in the current process.
  88   ChangeType PermanentStudyGroupChanged(const ProcessedStudy& processed_study,
  89                                         const std::string& selected_group);
  90
  91   // For the given |processed_study| with SESSION consistency, determines if
  92   // there are enough changes in the study config that restarting will result
  93   // in a guaranteed different group assignment (or different params) and
  94   // returns the corresponding ChangeType.
  95   ChangeType SessionStudyGroupChanged(const ProcessedStudy& filtered_study,
  96                                       const std::string& selected_group);
  97
  98   const base::FieldTrial::EntropyProvider& entropy_provider_;
  99
 100   DISALLOW_COPY_AND_ASSIGN(VariationsSeedSimulator);
 101 };
 102
 103 }  // namespace variations
 104
 105 #endif  // COMPONENTS_VARIATIONS_VARIATIONS_SEED_SIMULATOR_H_