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 76 matching lines @@
   // histograms will get unique names via the MakeName() methods.
   static const Probability kAllRemainingProbability;
 
   // The name is used to register the instance with the FieldTrialList class,
   // and can be used to find the trial (only one trial can be present for each
   // name).
   // Group probabilities that are later supplied must sum to less than or equal
   // to the total_probability.
   FieldTrial(const std::string& name, Probability total_probability);
 
+  // Determine if the field trial is to be disabled or not based on
+  // disable_duration_, build time of the module and Now(). This method sets
+  // disable_field_trail_ to true, if the difference between build time of the

[jar (doing other things), 2011/01/10 22:01:21]

nit: trail-->trial

[rtenneti, 2011/01/10 22:48:03]

Done.

+  // module and Now() is greater than disable_duration_. If disable_field_trail_
+  // is true then the field trial reverts to the 'default' bucket.
+  void FieldTrial::DetermineIfFieldTrailIsToBeDisabled();
+
   // Establish the name and probability of the next group in this trial.
   // Sometimes, based on construction randomization, this call may causes the
   // provided group to be *THE* group selected for use in this instance.
   int AppendGroup(const std::string& name, Probability group_probability);
 
   // Return the name of the FieldTrial (excluding the group name).
   std::string name() const { return name_; }
 
   // 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 from build time of the module to disable Field Trial.
+  void SetDisableDuration(const base::TimeDelta& duration);
+
+  base::TimeDelta disableDuration() const {

[jar (doing other things), 2011/01/10 22:01:21]

nit: Reading this name, it looks like the duration for which this will be
disabled, rather than the (much loo long name) duration until it will be
impossible to enable.

We need a better name forthe setter and slot.  Possibilities include:

InhibitDate
UsageTimeout
EnablementDeadline

WDYT?

[rtenneti, 2011/01/10 22:48:03]

Hi Jim,
  UsageTimeout seems to read better. Going with it. Hope that is ok.

thanks,
raman

[rtenneti, 2011/01/10 22:48:03]

Done.

+    return disable_duration_;
+  }
+
   // 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_;
 
+  // The default value (all remaining probabilities) can be selected after the
+  // duration, which is based on the build time of the module.
+  base::TimeDelta disable_duration_;
+
+  // When disable_field_trail_ is true, field trial reverts to the 'default'
+  // bucket.
+  bool disable_field_trail_;
+
   // 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_