disable field trials if the build is 30 days or older

base/metrics/field_trial.h

 // Copyright (c) 2011 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.
 
 // FieldTrial is a class for handling details of statistical experiments
 // performed by actual users in the field (i.e., in a shipped or beta product).
 // All code is called exclusively on the UI thread currently.
 //
 // The simplest example is an experiment to see whether one of two options
 // produces "better" results across our user population.  In that scenario, UMA
@@ skipping 94 matching lines @@
   // Return the randomly selected group number that was assigned.
   // Return kNotParticipating if the instance is not participating in the
   // experiment.
   int group() const { return group_; }
 
   // If the field trial is not in an experiment, this returns the empty string.
   // if the group's name is empty, a name of "_" concatenated with the group
   // number is used as the group name.
   std::string group_name() const { return group_name_; }
 
+  // Set the duration after which we will disable Field Trials. We will subtract
+  // build time from application start time and if the difference is greater
+  // than the duration that is specified via the following function, then we
+  // disable field trails and the field trials revert to the 'default' bucket.
+  void SetDurationAfterWhichDisableFieldTrials(base::TimeDelta duration) {

[jar (doing other things), 2011/01/09 07:00:04]

nit: for classes as arguments, pass in:
const CLASSNAME&

[jar (doing other things), 2011/01/09 07:00:04]

nit: Since this is an instance of FieldTrial, we only control this one single
field trial with this setting, so the name of the method should not end in an
"s" (we don't impact TrialS).

In fact, since this is a FieldTrial method, we probably don't need the
FieldTrial posfix.

That would get the name down to something like:

SetDurationAfterWhichDisabled

Which might even be written:

SetDisableDuration

The slot describing the corresponding member (disable_duration_??) would have a
comment that only the default value (all remaining probabilities) can be
selected after the duration, which is based on the build time of the module.

WDYT?

[rtenneti, 2011/01/09 23:16:42]

Done.

[rtenneti, 2011/01/09 23:16:42]

Done.

+    duration_after_which_disable_field_trials_ = duration;
+  }
+  base::TimeDelta durationAfterWhichDisableFieldTrials() {
+    return duration_after_which_disable_field_trials_;
+  }
+
   // Helper function for the most common use: as an argument to specifiy the
   // name of a HISTOGRAM.  Use the original histogram name as the name_prefix.
   static std::string MakeName(const std::string& name_prefix,
                               const std::string& trial_name);
 
   // Enable benchmarking sets field trials to a common setting.
   static void EnableBenchmarking();
 
+  // Get build time.
+  static Time GetBuildTime();
+
  private:
   friend class RefCounted<FieldTrial>;
 
   virtual ~FieldTrial();
 
   // The name of the field trial, as can be found via the FieldTrialList.
   // This is empty of the trial is not in the experiment.
   const std::string name_;
 
   // The maximum sum of all probabilities supplied, which corresponds to 100%.
   // This is the scaling factor used to adjust supplied probabilities.
   Probability divisor_;
 
   // The randomly selected probability that is used to select a group (or have
   // the instance not participate).  It is the product of divisor_ and a random
   // number between [0, 1).
   Probability random_;
 
   // Sum of the probabilities of all appended groups.
   Probability accumulated_group_probability_;
 
   int next_group_number_;
 
+  // duration after which we should disable field_trails.
+  base::TimeDelta duration_after_which_disable_field_trials_;
+
+  bool disable_field_trails_;
+
   // The pseudo-randomly assigned group number.
   // This is kNotParticipating if no group has been assigned.
   int group_;
 
   // A textual name for the randomly selected group, including the Trial name.
   // If this Trial is not a member of an group, this string is empty.
   std::string group_name_;
 
   // When benchmarking is enabled, field trials all revert to the 'default'
   // bucket.
@@ skipping 83 matching lines @@
   Lock lock_;
   RegistrationList registered_;
 
   DISALLOW_COPY_AND_ASSIGN(FieldTrialList);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_FIELD_TRIAL_H_