1 // Copyright (c) 2013 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/metrics/variations/uniformity_field_trials.h" 6 7 #include "base/metrics/field_trial.h" 8 #include "base/strings/stringprintf.h" 9 #include "base/time/time.h" 10 #include "chrome/common/metrics/variations/variations_util.h" 11 12 namespace chrome_variations { 13 14 namespace { 15 16 // Set up a uniformity field trial. |one_time_randomized| indicates if the 17 // field trial is one-time randomized or session-randomized. |trial_name_string| 18 // must contain a "%d" since the percentage of the group will be inserted in 19 // the trial name. |num_trial_groups| must be a divisor of 100 (e.g. 5, 20) 20 void SetupSingleUniformityFieldTrial( 21 base::FieldTrial::RandomizationType randomization_type, 22 const std::string& trial_name_string, 23 const VariationID trial_base_id, 24 int num_trial_groups) { 25 // Probability per group remains constant for all uniformity trials, what 26 // changes is the probability divisor. 27 static const base::FieldTrial::Probability kProbabilityPerGroup = 1; 28 const std::string kDefaultGroupName = "default"; 29 const base::FieldTrial::Probability divisor = num_trial_groups; 30 31 DCHECK_EQ(100 % num_trial_groups, 0); 32 const int group_percent = 100 / num_trial_groups; 33 const std::string trial_name = base::StringPrintf(trial_name_string.c_str(), 34 group_percent); 35 36 DVLOG(1) << "Trial name = " << trial_name; 37 38 scoped_refptr<base::FieldTrial> trial( 39 base::FieldTrialList::FactoryGetFieldTrial( 40 trial_name, divisor, kDefaultGroupName, 2015, 1, 1, 41 randomization_type, NULL)); 42 AssociateGoogleVariationID(GOOGLE_UPDATE_SERVICE, trial_name, 43 kDefaultGroupName, trial_base_id); 44 45 // Loop starts with group 1 because the field trial automatically creates a 46 // default group, which would be group 0. 47 for (int group_number = 1; group_number < num_trial_groups; ++group_number) { 48 const std::string group_name = 49 base::StringPrintf("group_%02d", group_number); 50 DVLOG(1) << " Group name = " << group_name; 51 trial->AppendGroup(group_name, kProbabilityPerGroup); 52 AssociateGoogleVariationID( 53 GOOGLE_UPDATE_SERVICE, trial_name, group_name, 54 static_cast<VariationID>(trial_base_id + group_number)); 55 } 56 57 // Now that all groups have been appended, call group() on the trial to 58 // ensure that our trial is registered. This resolves an off-by-one issue 59 // where the default group never gets chosen if we don't "use" the trial. 60 const int chosen_group = trial->group(); 61 DVLOG(1) << "Chosen Group: " << chosen_group; 62 } 63 64 // Setup a 50% uniformity trial for new installs only. This is accomplished by 65 // disabling the trial on clients that were installed before a specified date. 66 void SetupNewInstallUniformityTrial(const base::Time install_date) { 67 const base::Time::Exploded kStartDate = { 68 2012, 11, 0, 6, // Nov 6, 2012 69 0, 0, 0, 0 // 00:00:00.000 70 }; 71 scoped_refptr<base::FieldTrial> trial( 72 base::FieldTrialList::FactoryGetFieldTrial( 73 "UMA-New-Install-Uniformity-Trial", 100, "Disabled", 74 2015, 1, 1, base::FieldTrial::ONE_TIME_RANDOMIZED, NULL)); 75 trial->AppendGroup("Control", 50); 76 trial->AppendGroup("Experiment", 50); 77 const base::Time start_date = base::Time::FromLocalExploded(kStartDate); 78 if (install_date < start_date) 79 trial->Disable(); 80 else 81 trial->group(); 82 } 83 84 } // namespace 85 86 void SetupUniformityFieldTrials(const base::Time install_date) { 87 // The 100 percent field trial in which everyone is a member is a special 88 // case. It is useful to create as it permits viewing all UMA data in UIs 89 // and tools that require a field trial. 90 base::FieldTrial* trial = 91 base::FieldTrialList::CreateFieldTrial("UMA-Uniformity-Trial-100-Percent", 92 "group_01"); 93 // Call |group()| on the trial to ensure its reported in metrics. 94 trial->group(); 95 96 // One field trial will be created for each entry in this array. The i'th 97 // field trial will have |trial_sizes[i]| groups in it, including the default 98 // group. Each group will have a probability of 1/|trial_sizes[i]|. 99 const int num_trial_groups[] = { 100, 20, 10, 5, 2 }; 100 101 // Declare our variation ID bases along side this array so we can loop over it 102 // and assign the IDs appropriately. So for example, the 1 percent experiments 103 // should have a size of 100 (100/100 = 1). 104 const VariationID trial_base_ids[] = { 105 UNIFORMITY_1_PERCENT_BASE, 106 UNIFORMITY_5_PERCENT_BASE, 107 UNIFORMITY_10_PERCENT_BASE, 108 UNIFORMITY_20_PERCENT_BASE, 109 UNIFORMITY_50_PERCENT_BASE 110 }; 111 112 const std::string kOneTimeRandomizedTrialName = 113 "UMA-Uniformity-Trial-%d-Percent"; 114 for (size_t i = 0; i < arraysize(num_trial_groups); ++i) { 115 SetupSingleUniformityFieldTrial(base::FieldTrial::ONE_TIME_RANDOMIZED, 116 kOneTimeRandomizedTrialName, 117 trial_base_ids[i], num_trial_groups[i]); 118 } 119 120 // Setup a 5% session-randomized uniformity trial. 121 const std::string kSessionRandomizedTrialName = 122 "UMA-Session-Randomized-Uniformity-Trial-%d-Percent"; 123 SetupSingleUniformityFieldTrial( 124 base::FieldTrial::SESSION_RANDOMIZED, kSessionRandomizedTrialName, 125 UNIFORMITY_SESSION_RANDOMIZED_5_PERCENT_BASE, 20); 126 127 SetupNewInstallUniformityTrial(install_date); 128 } 129 130 } // namespace chrome_variations 131
