src/chrome/common/variations/uniformity_field_trials.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 "chrome/common/variations/uniformity_field_trials.h"
   6
   7 #include <string>
   8
   9 #include "base/metrics/field_trial.h"
  10 #include "base/strings/stringprintf.h"
  11 #include "base/time/time.h"
  12 #include "components/variations/variations_associated_data.h"
  13
  14 namespace chrome_variations {
  15
  16 namespace {
  17
  18 const int MINIMIUM_ID = 3300000;
  19
  20 const int UNIFORMITY_1_PERCENT_BASE  = MINIMIUM_ID;
  21 const int UNIFORMITY_1_PERCENT_LIMIT = UNIFORMITY_1_PERCENT_BASE + 100;
  22 const int UNIFORMITY_5_PERCENT_BASE  = UNIFORMITY_1_PERCENT_LIMIT;
  23 const int UNIFORMITY_5_PERCENT_LIMIT = UNIFORMITY_5_PERCENT_BASE + 20;
  24 const int UNIFORMITY_10_PERCENT_BASE  = UNIFORMITY_5_PERCENT_LIMIT;
  25 const int UNIFORMITY_10_PERCENT_LIMIT = UNIFORMITY_10_PERCENT_BASE + 10;
  26 const int UNIFORMITY_20_PERCENT_BASE  = UNIFORMITY_10_PERCENT_LIMIT;
  27 const int UNIFORMITY_20_PERCENT_LIMIT = UNIFORMITY_20_PERCENT_BASE + 5;
  28 const int UNIFORMITY_50_PERCENT_BASE  = UNIFORMITY_20_PERCENT_LIMIT;
  29 // A uniformity trial used to compare one-time-randomized and
  30 // session-randomized FieldTrials.
  31 const int UNIFORMITY_SESSION_RANDOMIZED_5_PERCENT_BASE  = 3300139;
  32
  33 // Set up a uniformity field trial. |one_time_randomized| indicates if the
  34 // field trial is one-time randomized or session-randomized. |trial_name_string|
  35 // must contain a "%d" since the percentage of the group will be inserted in
  36 // the trial name. |num_trial_groups| must be a divisor of 100 (e.g. 5, 20)
  37 void SetupSingleUniformityFieldTrial(
  38     base::FieldTrial::RandomizationType randomization_type,
  39     const std::string& trial_name_string,
  40     const variations::VariationID trial_base_id,
  41     int num_trial_groups) {
  42   // Probability per group remains constant for all uniformity trials, what
  43   // changes is the probability divisor.
  44   static const base::FieldTrial::Probability kProbabilityPerGroup = 1;
  45   const std::string kDefaultGroupName = "default";
  46   const base::FieldTrial::Probability divisor = num_trial_groups;
  47
  48   DCHECK_EQ(100 % num_trial_groups, 0);
  49   const int group_percent = 100 / num_trial_groups;
  50   const std::string trial_name = base::StringPrintf(trial_name_string.c_str(),
  51                                                     group_percent);
  52
  53   DVLOG(1) << "Trial name = " << trial_name;
  54
  55   scoped_refptr<base::FieldTrial> trial(
  56       base::FieldTrialList::FactoryGetFieldTrial(
  57           trial_name, divisor, kDefaultGroupName, 2015, 1, 1,
  58           randomization_type, NULL));
  59   variations::AssociateGoogleVariationID(variations::GOOGLE_UPDATE_SERVICE,
  60                                          trial_name, kDefaultGroupName,
  61                                          trial_base_id);
  62
  63   // Loop starts with group 1 because the field trial automatically creates a
  64   // default group, which would be group 0.
  65   for (int group_number = 1; group_number < num_trial_groups; ++group_number) {
  66     const std::string group_name =
  67           base::StringPrintf("group_%02d", group_number);
  68     DVLOG(1) << "    Group name = " << group_name;
  69     trial->AppendGroup(group_name, kProbabilityPerGroup);
  70     variations::AssociateGoogleVariationID(
  71         variations::GOOGLE_UPDATE_SERVICE, trial_name, group_name,
  72         static_cast<variations::VariationID>(trial_base_id + group_number));
  73   }
  74
  75   // Now that all groups have been appended, call group() on the trial to
  76   // ensure that our trial is registered. This resolves an off-by-one issue
  77   // where the default group never gets chosen if we don't "use" the trial.
  78   const int chosen_group = trial->group();
  79   DVLOG(1) << "Chosen Group: " << chosen_group;
  80 }
  81
  82 // Setup a 50% uniformity trial for new installs only. This is accomplished by
  83 // disabling the trial on clients that were installed before a specified date.
  84 void SetupNewInstallUniformityTrial(const base::Time install_date) {
  85   const base::Time::Exploded kStartDate = {
  86     2012, 11, 0, 6,  // Nov 6, 2012
  87     0, 0, 0, 0       // 00:00:00.000
  88   };
  89   scoped_refptr<base::FieldTrial> trial(
  90       base::FieldTrialList::FactoryGetFieldTrial(
  91           "UMA-New-Install-Uniformity-Trial", 100, "Disabled",
  92           2015, 1, 1, base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
  93   trial->AppendGroup("Control", 50);
  94   trial->AppendGroup("Experiment", 50);
  95   const base::Time start_date = base::Time::FromLocalExploded(kStartDate);
  96   if (install_date < start_date)
  97     trial->Disable();
  98   else
  99     trial->group();
 100 }
 101
 102 }  // namespace
 103
 104 void SetupUniformityFieldTrials(const base::Time install_date) {
 105   // The 100 percent field trial in which everyone is a member is a special
 106   // case. It is useful to create as it permits viewing all UMA data in UIs
 107   // and tools that require a field trial.
 108   base::FieldTrial* trial =
 109       base::FieldTrialList::CreateFieldTrial("UMA-Uniformity-Trial-100-Percent",
 110                                              "group_01");
 111   // Call |group()| on the trial to ensure its reported in metrics.
 112   trial->group();
 113
 114   // One field trial will be created for each entry in this array. The i'th
 115   // field trial will have |trial_sizes[i]| groups in it, including the default
 116   // group. Each group will have a probability of 1/|trial_sizes[i]|.
 117   const int num_trial_groups[] = { 100, 20, 10, 5, 2 };
 118
 119   // Declare our variation ID bases along side this array so we can loop over it
 120   // and assign the IDs appropriately. So for example, the 1 percent experiments
 121   // should have a size of 100 (100/100 = 1).
 122   const variations::VariationID trial_base_ids[] = {
 123     UNIFORMITY_1_PERCENT_BASE,
 124     UNIFORMITY_5_PERCENT_BASE,
 125     UNIFORMITY_10_PERCENT_BASE,
 126     UNIFORMITY_20_PERCENT_BASE,
 127     UNIFORMITY_50_PERCENT_BASE
 128   };
 129
 130   const std::string kOneTimeRandomizedTrialName =
 131       "UMA-Uniformity-Trial-%d-Percent";
 132   for (size_t i = 0; i < arraysize(num_trial_groups); ++i) {
 133     SetupSingleUniformityFieldTrial(base::FieldTrial::ONE_TIME_RANDOMIZED,
 134                                     kOneTimeRandomizedTrialName,
 135                                     trial_base_ids[i], num_trial_groups[i]);
 136   }
 137
 138   // Setup a 5% session-randomized uniformity trial.
 139   const std::string kSessionRandomizedTrialName =
 140       "UMA-Session-Randomized-Uniformity-Trial-%d-Percent";
 141   SetupSingleUniformityFieldTrial(
 142       base::FieldTrial::SESSION_RANDOMIZED, kSessionRandomizedTrialName,
 143       UNIFORMITY_SESSION_RANDOMIZED_5_PERCENT_BASE, 20);
 144
 145   SetupNewInstallUniformityTrial(install_date);
 146 }
 147
 148 }  // namespace chrome_variations