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authorasvitkine@chromium.org <asvitkine@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98>2013-07-30 15:11:29 +0000
committerasvitkine@chromium.org <asvitkine@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98>2013-07-30 15:11:29 +0000
commitebcf69f02f4f02e508e77193e51dd6557e6c0085 (patch)
tree80f883eca03bd26b3a5211f9156ff2e860c909ff /base/metrics/field_trial.h
parentb554d462229e4498ba6576d7cd0c2336fb468175 (diff)
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Make field trial randomization type a constructor param.
Changes the Field Trial API to require users to pass ONE_TIME_RANDOMIZED or SESSION_RANDOMIZED at the time the field trial is created. This removes a source of human errors, where developers would sometimes previously forget to call UseOneTimeRandomization() in their CLs. It's a small startup performance win, since one time randomized trials will no longer call RandDouble() that will be then replaced by a value from the entropy provider. (This was showing up in profiles when I was measuring metrics startup perf on mobile.) BUG=262971 TEST=Existing unit tests. TBR=isherman@chromium.org, thakis@chromium.org Review URL: https://codereview.chromium.org/20777005 git-svn-id: svn://svn.chromium.org/chrome/trunk/src@214352 0039d316-1c4b-4281-b951-d872f2087c98
Diffstat (limited to 'base/metrics/field_trial.h')
-rw-r--r--base/metrics/field_trial.h75
1 files changed, 45 insertions, 30 deletions
diff --git a/base/metrics/field_trial.h b/base/metrics/field_trial.h
index 106bf8b..08a8406 100644
--- a/base/metrics/field_trial.h
+++ b/base/metrics/field_trial.h
@@ -15,11 +15,9 @@
// States are typically generated randomly, either based on a one time
// randomization (which will yield the same results, in terms of selecting
// the client for a field trial or not, for every run of the program on a
-// given machine), or by a startup randomization (generated each time the
+// given machine), or by a session randomization (generated each time the
// application starts up, but held constant during the duration of the
-// process), or by continuous randomization across a run (where the state
-// can be recalculated again and again, many times during a process).
-// Continuous randomization is not yet implemented.
+// process).
//------------------------------------------------------------------------------
// Example: Suppose we have an experiment involving memory, such as determining
@@ -37,9 +35,10 @@
// // Note: This field trial will run in Chrome instances compiled through
// // 8 July, 2015, and after that all instances will be in "StandardMem".
// scoped_refptr<base::FieldTrial> trial(
-// base::FieldTrialList::FactoryGetFieldTrial("MemoryExperiment", 1000,
-// "StandardMem", 2015, 7, 8,
-// NULL));
+// base::FieldTrialList::FactoryGetFieldTrial(
+// "MemoryExperiment", 1000, "StandardMem", 2015, 7, 8,
+// base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
+//
// const int high_mem_group =
// trial->AppendGroup("HighMem", 20); // 2% in HighMem group.
// const int low_mem_group =
@@ -95,6 +94,17 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
public:
typedef int Probability; // Probability type for being selected in a trial.
+ // Specifies the persistence of the field trial group choice.
+ enum RandomizationType {
+ // One time randomized trials will persist the group choice between
+ // restarts, which is recommended for most trials, especially those that
+ // change user visible behavior.
+ ONE_TIME_RANDOMIZED,
+ // Session randomized trials will roll the dice to select a group on every
+ // process restart.
+ SESSION_RANDOMIZED,
+ };
+
// EntropyProvider is an interface for providing entropy for one-time
// randomized (persistent) field trials.
class BASE_EXPORT EntropyProvider {
@@ -122,21 +132,6 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
// assignment (and hence is not yet participating in the trial).
static const int kNotFinalized;
- // Changes the field trial to use one-time randomization, i.e. produce the
- // same result for the current trial on every run of this client. Must be
- // called right after construction, before any groups are added.
- void UseOneTimeRandomization();
-
- // Changes the field trial to use one-time randomization, i.e. produce the
- // same result for the current trial on every run of this client, with a
- // custom randomization seed for the trial (instead of a hash of the trial
- // name, which is used otherwise). The |randomization_seed| value should never
- // be the same for two trials, else this would result in correlated group
- // assignments. Note: Using a custom randomization seed is only supported by
- // the PermutedEntropyProvider (which is used when UMA is not enabled). Must
- // be called right after construction, before any groups are added.
- void UseOneTimeRandomizationWithCustomSeed(uint32 randomization_seed);
-
// Disables this trial, meaning it always determines the default group
// has been selected. May be called immediately after construction, or
// at any time after initialization (should not be interleaved with
@@ -201,7 +196,6 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, HashClientId);
FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, HashClientIdIsUniform);
FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, NameGroupIds);
- FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, UseOneTimeRandomization);
FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, SetForcedTurnFeatureOff);
FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, SetForcedTurnFeatureOn);
FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, SetForcedChangeDefault_Default);
@@ -216,9 +210,12 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
// consumers don't use it by mistake in cases where the group was forced.
static const int kDefaultGroupNumber;
+ // Creates a field trial with the specified parameters. Group assignment will
+ // be done based on |entropy_value|, which must have a range of [0, 1).
FieldTrial(const std::string& name,
Probability total_probability,
- const std::string& default_group_name);
+ const std::string& default_group_name,
+ double entropy_value);
virtual ~FieldTrial();
// Return the default group name of the FieldTrial.
@@ -350,8 +347,7 @@ class BASE_EXPORT FieldTrialList {
// then the field trial reverts to the 'default' group.
//
// Use this static method to get a startup-randomized FieldTrial or a
- // previously created forced FieldTrial. If you want a one-time randomized
- // trial, call UseOneTimeRandomization() right after creation.
+ // previously created forced FieldTrial.
static FieldTrial* FactoryGetFieldTrial(
const std::string& trial_name,
FieldTrial::Probability total_probability,
@@ -359,6 +355,25 @@ class BASE_EXPORT FieldTrialList {
const int year,
const int month,
const int day_of_month,
+ FieldTrial::RandomizationType randomization_type,
+ int* default_group_number);
+
+ // Same as FactoryGetFieldTrial(), but allows specifying a custom seed to be
+ // used on one-time randomized field trials (instead of a hash of the trial
+ // name, which is used otherwise or if |randomization_seed| has value 0). The
+ // |randomization_seed| value (other than 0) should never be the same for two
+ // trials, else this would result in correlated group assignments.
+ // Note: Using a custom randomization seed is only supported by the
+ // PermutedEntropyProvider (which is used when UMA is not enabled).
+ static FieldTrial* FactoryGetFieldTrialWithRandomizationSeed(
+ const std::string& trial_name,
+ FieldTrial::Probability total_probability,
+ const std::string& default_group_name,
+ const int year,
+ const int month,
+ const int day_of_month,
+ FieldTrial::RandomizationType randomization_type,
+ uint32 randomization_seed,
int* default_group_number);
// The Find() method can be used to test to see if a named Trial was already
@@ -427,15 +442,15 @@ class BASE_EXPORT FieldTrialList {
// Return the number of active field trials.
static size_t GetFieldTrialCount();
+ private:
+ // A map from FieldTrial names to the actual instances.
+ typedef std::map<std::string, FieldTrial*> RegistrationList;
+
// If one-time randomization is enabled, returns a weak pointer to the
// corresponding EntropyProvider. Otherwise, returns NULL.
static const FieldTrial::EntropyProvider*
GetEntropyProviderForOneTimeRandomization();
- private:
- // A map from FieldTrial names to the actual instances.
- typedef std::map<std::string, FieldTrial*> RegistrationList;
-
// Helper function should be called only while holding lock_.
FieldTrial* PreLockedFind(const std::string& name);
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