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