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field_trial.cc
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field_trial.cc
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// Copyright (c) 2012 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.
#include "base/metrics/field_trial.h"
#include <algorithm>
#include <utility>
#include "base/base_switches.h"
#include "base/build_time.h"
#include "base/command_line.h"
#include "base/debug/activity_tracker.h"
#include "base/logging.h"
#include "base/metrics/field_trial_param_associator.h"
#include "base/process/memory.h"
#include "base/process/process_handle.h"
#include "base/process/process_info.h"
#include "base/rand_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_split.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
#include "base/unguessable_token.h"
// On POSIX, the fd is shared using the mapping in GlobalDescriptors.
#if defined(OS_POSIX) && !defined(OS_NACL)
#include "base/posix/global_descriptors.h"
#endif
namespace base {
namespace {
// Define a separator character to use when creating a persistent form of an
// instance. This is intended for use as a command line argument, passed to a
// second process to mimic our state (i.e., provide the same group name).
const char kPersistentStringSeparator = '/'; // Currently a slash.
// Define a marker character to be used as a prefix to a trial name on the
// command line which forces its activation.
const char kActivationMarker = '*';
// Use shared memory to communicate field trial (experiment) state. Set to false
// for now while the implementation is fleshed out (e.g. data format, single
// shared memory segment). See https://codereview.chromium.org/2365273004/ and
// crbug.com/653874
// The browser is the only process that has write access to the shared memory.
// This is safe from race conditions because MakeIterable is a release operation
// and GetNextOfType is an acquire operation, so memory writes before
// MakeIterable happen before memory reads after GetNextOfType.
#if defined(OS_FUCHSIA) // TODO(752368): Not yet supported on Fuchsia.
const bool kUseSharedMemoryForFieldTrials = false;
#else
const bool kUseSharedMemoryForFieldTrials = true;
#endif
// Constants for the field trial allocator.
const char kAllocatorName[] = "FieldTrialAllocator";
// We allocate 128 KiB to hold all the field trial data. This should be enough,
// as most people use 3 - 25 KiB for field trials (as of 11/25/2016).
// This also doesn't allocate all 128 KiB at once -- the pages only get mapped
// to physical memory when they are touched. If the size of the allocated field
// trials does get larger than 128 KiB, then we will drop some field trials in
// child processes, leading to an inconsistent view between browser and child
// processes and possibly causing crashes (see crbug.com/661617).
const size_t kFieldTrialAllocationSize = 128 << 10; // 128 KiB
// Writes out string1 and then string2 to pickle.
void WriteStringPair(Pickle* pickle,
const StringPiece& string1,
const StringPiece& string2) {
pickle->WriteString(string1);
pickle->WriteString(string2);
}
// Writes out the field trial's contents (via trial_state) to the pickle. The
// format of the pickle looks like:
// TrialName, GroupName, ParamKey1, ParamValue1, ParamKey2, ParamValue2, ...
// If there are no parameters, then it just ends at GroupName.
void PickleFieldTrial(const FieldTrial::State& trial_state, Pickle* pickle) {
WriteStringPair(pickle, *trial_state.trial_name, *trial_state.group_name);
// Get field trial params.
std::map<std::string, std::string> params;
FieldTrialParamAssociator::GetInstance()->GetFieldTrialParamsWithoutFallback(
*trial_state.trial_name, *trial_state.group_name, ¶ms);
// Write params to pickle.
for (const auto& param : params)
WriteStringPair(pickle, param.first, param.second);
}
// Created a time value based on |year|, |month| and |day_of_month| parameters.
Time CreateTimeFromParams(int year, int month, int day_of_month) {
DCHECK_GT(year, 1970);
DCHECK_GT(month, 0);
DCHECK_LT(month, 13);
DCHECK_GT(day_of_month, 0);
DCHECK_LT(day_of_month, 32);
Time::Exploded exploded;
exploded.year = year;
exploded.month = month;
exploded.day_of_week = 0; // Should be unused.
exploded.day_of_month = day_of_month;
exploded.hour = 0;
exploded.minute = 0;
exploded.second = 0;
exploded.millisecond = 0;
Time out_time;
if (!Time::FromLocalExploded(exploded, &out_time)) {
// TODO(maksims): implement failure handling.
// We might just return |out_time|, which is Time(0).
NOTIMPLEMENTED();
}
return out_time;
}
// Returns the boundary value for comparing against the FieldTrial's added
// groups for a given |divisor| (total probability) and |entropy_value|.
FieldTrial::Probability GetGroupBoundaryValue(
FieldTrial::Probability divisor,
double entropy_value) {
// Add a tiny epsilon value to get consistent results when converting floating
// points to int. Without it, boundary values have inconsistent results, e.g.:
//
// static_cast<FieldTrial::Probability>(100 * 0.56) == 56
// static_cast<FieldTrial::Probability>(100 * 0.57) == 56
// static_cast<FieldTrial::Probability>(100 * 0.58) == 57
// static_cast<FieldTrial::Probability>(100 * 0.59) == 59
const double kEpsilon = 1e-8;
const FieldTrial::Probability result =
static_cast<FieldTrial::Probability>(divisor * entropy_value + kEpsilon);
// Ensure that adding the epsilon still results in a value < |divisor|.
return std::min(result, divisor - 1);
}
// Separate type from FieldTrial::State so that it can use StringPieces.
struct FieldTrialStringEntry {
StringPiece trial_name;
StringPiece group_name;
bool activated = false;
};
// Parses the --force-fieldtrials string |trials_string| into |entries|.
// Returns true if the string was parsed correctly. On failure, the |entries|
// array may end up being partially filled.
bool ParseFieldTrialsString(const std::string& trials_string,
std::vector<FieldTrialStringEntry>* entries) {
const StringPiece trials_string_piece(trials_string);
size_t next_item = 0;
while (next_item < trials_string.length()) {
size_t name_end = trials_string.find(kPersistentStringSeparator, next_item);
if (name_end == trials_string.npos || next_item == name_end)
return false;
size_t group_name_end =
trials_string.find(kPersistentStringSeparator, name_end + 1);
if (name_end + 1 == group_name_end)
return false;
if (group_name_end == trials_string.npos)
group_name_end = trials_string.length();
FieldTrialStringEntry entry;
// Verify if the trial should be activated or not.
if (trials_string[next_item] == kActivationMarker) {
// Name cannot be only the indicator.
if (name_end - next_item == 1)
return false;
next_item++;
entry.activated = true;
}
entry.trial_name =
trials_string_piece.substr(next_item, name_end - next_item);
entry.group_name =
trials_string_piece.substr(name_end + 1, group_name_end - name_end - 1);
next_item = group_name_end + 1;
entries->push_back(std::move(entry));
}
return true;
}
void AddFeatureAndFieldTrialFlags(const char* enable_features_switch,
const char* disable_features_switch,
CommandLine* cmd_line) {
std::string enabled_features;
std::string disabled_features;
FeatureList::GetInstance()->GetFeatureOverrides(&enabled_features,
&disabled_features);
if (!enabled_features.empty())
cmd_line->AppendSwitchASCII(enable_features_switch, enabled_features);
if (!disabled_features.empty())
cmd_line->AppendSwitchASCII(disable_features_switch, disabled_features);
std::string field_trial_states;
FieldTrialList::AllStatesToString(&field_trial_states);
if (!field_trial_states.empty()) {
cmd_line->AppendSwitchASCII(switches::kForceFieldTrials,
field_trial_states);
}
}
void OnOutOfMemory(size_t size) {
#if defined(OS_NACL)
NOTREACHED();
#else
TerminateBecauseOutOfMemory(size);
#endif
}
#if !defined(OS_NACL)
// Returns whether the operation succeeded.
bool DeserializeGUIDFromStringPieces(base::StringPiece first,
base::StringPiece second,
base::UnguessableToken* guid) {
uint64_t high = 0;
uint64_t low = 0;
if (!base::StringToUint64(first, &high) ||
!base::StringToUint64(second, &low)) {
return false;
}
*guid = base::UnguessableToken::Deserialize(high, low);
return true;
}
#endif
} // namespace
// statics
const int FieldTrial::kNotFinalized = -1;
const int FieldTrial::kDefaultGroupNumber = 0;
bool FieldTrial::enable_benchmarking_ = false;
int FieldTrialList::kNoExpirationYear = 0;
//------------------------------------------------------------------------------
// FieldTrial methods and members.
FieldTrial::EntropyProvider::~EntropyProvider() {
}
FieldTrial::State::State() {}
FieldTrial::State::State(const State& other) = default;
FieldTrial::State::~State() {}
bool FieldTrial::FieldTrialEntry::GetTrialAndGroupName(
StringPiece* trial_name,
StringPiece* group_name) const {
PickleIterator iter = GetPickleIterator();
return ReadStringPair(&iter, trial_name, group_name);
}
bool FieldTrial::FieldTrialEntry::GetParams(
std::map<std::string, std::string>* params) const {
PickleIterator iter = GetPickleIterator();
StringPiece tmp;
// Skip reading trial and group name.
if (!ReadStringPair(&iter, &tmp, &tmp))
return false;
while (true) {
StringPiece key;
StringPiece value;
if (!ReadStringPair(&iter, &key, &value))
return key.empty(); // Non-empty is bad: got one of a pair.
(*params)[key.as_string()] = value.as_string();
}
}
PickleIterator FieldTrial::FieldTrialEntry::GetPickleIterator() const {
const char* src =
reinterpret_cast<const char*>(this) + sizeof(FieldTrialEntry);
Pickle pickle(src, pickle_size);
return PickleIterator(pickle);
}
bool FieldTrial::FieldTrialEntry::ReadStringPair(
PickleIterator* iter,
StringPiece* trial_name,
StringPiece* group_name) const {
if (!iter->ReadStringPiece(trial_name))
return false;
if (!iter->ReadStringPiece(group_name))
return false;
return true;
}
void FieldTrial::Disable() {
DCHECK(!group_reported_);
enable_field_trial_ = false;
// In case we are disabled after initialization, we need to switch
// the trial to the default group.
if (group_ != kNotFinalized) {
// Only reset when not already the default group, because in case we were
// forced to the default group, the group number may not be
// kDefaultGroupNumber, so we should keep it as is.
if (group_name_ != default_group_name_)
SetGroupChoice(default_group_name_, kDefaultGroupNumber);
}
}
int FieldTrial::AppendGroup(const std::string& name,
Probability group_probability) {
// When the group choice was previously forced, we only need to return the
// the id of the chosen group, and anything can be returned for the others.
if (forced_) {
DCHECK(!group_name_.empty());
if (name == group_name_) {
// Note that while |group_| may be equal to |kDefaultGroupNumber| on the
// forced trial, it will not have the same value as the default group
// number returned from the non-forced |FactoryGetFieldTrial()| call,
// which takes care to ensure that this does not happen.
return group_;
}
DCHECK_NE(next_group_number_, group_);
// We still return different numbers each time, in case some caller need
// them to be different.
return next_group_number_++;
}
DCHECK_LE(group_probability, divisor_);
DCHECK_GE(group_probability, 0);
if (enable_benchmarking_ || !enable_field_trial_)
group_probability = 0;
accumulated_group_probability_ += group_probability;
DCHECK_LE(accumulated_group_probability_, divisor_);
if (group_ == kNotFinalized && accumulated_group_probability_ > random_) {
// This is the group that crossed the random line, so we do the assignment.
SetGroupChoice(name, next_group_number_);
}
return next_group_number_++;
}
int FieldTrial::group() {
FinalizeGroupChoice();
if (trial_registered_)
FieldTrialList::NotifyFieldTrialGroupSelection(this);
return group_;
}
const std::string& FieldTrial::group_name() {
// Call |group()| to ensure group gets assigned and observers are notified.
group();
DCHECK(!group_name_.empty());
return group_name_;
}
const std::string& FieldTrial::GetGroupNameWithoutActivation() {
FinalizeGroupChoice();
return group_name_;
}
void FieldTrial::SetForced() {
// We might have been forced before (e.g., by CreateFieldTrial) and it's
// first come first served, e.g., command line switch has precedence.
if (forced_)
return;
// And we must finalize the group choice before we mark ourselves as forced.
FinalizeGroupChoice();
forced_ = true;
}
// static
void FieldTrial::EnableBenchmarking() {
DCHECK_EQ(0u, FieldTrialList::GetFieldTrialCount());
enable_benchmarking_ = true;
}
// static
FieldTrial* FieldTrial::CreateSimulatedFieldTrial(
const std::string& trial_name,
Probability total_probability,
const std::string& default_group_name,
double entropy_value) {
return new FieldTrial(trial_name, total_probability, default_group_name,
entropy_value);
}
FieldTrial::FieldTrial(const std::string& trial_name,
const Probability total_probability,
const std::string& default_group_name,
double entropy_value)
: trial_name_(trial_name),
divisor_(total_probability),
default_group_name_(default_group_name),
random_(GetGroupBoundaryValue(total_probability, entropy_value)),
accumulated_group_probability_(0),
next_group_number_(kDefaultGroupNumber + 1),
group_(kNotFinalized),
enable_field_trial_(true),
forced_(false),
group_reported_(false),
trial_registered_(false),
ref_(FieldTrialList::FieldTrialAllocator::kReferenceNull) {
DCHECK_GT(total_probability, 0);
DCHECK(!trial_name_.empty());
DCHECK(!default_group_name_.empty())
<< "Trial " << trial_name << " is missing a default group name.";
}
FieldTrial::~FieldTrial() {}
void FieldTrial::SetTrialRegistered() {
DCHECK_EQ(kNotFinalized, group_);
DCHECK(!trial_registered_);
trial_registered_ = true;
}
void FieldTrial::SetGroupChoice(const std::string& group_name, int number) {
group_ = number;
if (group_name.empty())
StringAppendF(&group_name_, "%d", group_);
else
group_name_ = group_name;
DVLOG(1) << "Field trial: " << trial_name_ << " Group choice:" << group_name_;
}
void FieldTrial::FinalizeGroupChoice() {
FinalizeGroupChoiceImpl(false);
}
void FieldTrial::FinalizeGroupChoiceImpl(bool is_locked) {
if (group_ != kNotFinalized)
return;
accumulated_group_probability_ = divisor_;
// Here it's OK to use |kDefaultGroupNumber| since we can't be forced and not
// finalized.
DCHECK(!forced_);
SetGroupChoice(default_group_name_, kDefaultGroupNumber);
// Add the field trial to shared memory.
if (kUseSharedMemoryForFieldTrials && trial_registered_)
FieldTrialList::OnGroupFinalized(is_locked, this);
}
bool FieldTrial::GetActiveGroup(ActiveGroup* active_group) const {
if (!group_reported_ || !enable_field_trial_)
return false;
DCHECK_NE(group_, kNotFinalized);
active_group->trial_name = trial_name_;
active_group->group_name = group_name_;
return true;
}
bool FieldTrial::GetState(State* field_trial_state) {
if (!enable_field_trial_)
return false;
FinalizeGroupChoice();
field_trial_state->trial_name = &trial_name_;
field_trial_state->group_name = &group_name_;
field_trial_state->activated = group_reported_;
return true;
}
bool FieldTrial::GetStateWhileLocked(State* field_trial_state) {
if (!enable_field_trial_)
return false;
FinalizeGroupChoiceImpl(true);
field_trial_state->trial_name = &trial_name_;
field_trial_state->group_name = &group_name_;
field_trial_state->activated = group_reported_;
return true;
}
//------------------------------------------------------------------------------
// FieldTrialList methods and members.
// static
FieldTrialList* FieldTrialList::global_ = nullptr;
// static
bool FieldTrialList::used_without_global_ = false;
FieldTrialList::Observer::~Observer() {
}
FieldTrialList::FieldTrialList(
std::unique_ptr<const FieldTrial::EntropyProvider> entropy_provider)
: entropy_provider_(std::move(entropy_provider)),
observer_list_(new ObserverListThreadSafe<FieldTrialList::Observer>(
ObserverListBase<FieldTrialList::Observer>::NOTIFY_EXISTING_ONLY)) {
DCHECK(!global_);
DCHECK(!used_without_global_);
global_ = this;
Time two_years_from_build_time = GetBuildTime() + TimeDelta::FromDays(730);
Time::Exploded exploded;
two_years_from_build_time.LocalExplode(&exploded);
kNoExpirationYear = exploded.year;
}
FieldTrialList::~FieldTrialList() {
AutoLock auto_lock(lock_);
while (!registered_.empty()) {
RegistrationMap::iterator it = registered_.begin();
it->second->Release();
registered_.erase(it->first);
}
DCHECK_EQ(this, global_);
global_ = nullptr;
}
// static
FieldTrial* FieldTrialList::FactoryGetFieldTrial(
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,
int* default_group_number) {
return FactoryGetFieldTrialWithRandomizationSeed(
trial_name, total_probability, default_group_name, year, month,
day_of_month, randomization_type, 0, default_group_number, nullptr);
}
// static
FieldTrial* FieldTrialList::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_t randomization_seed,
int* default_group_number,
const FieldTrial::EntropyProvider* override_entropy_provider) {
if (default_group_number)
*default_group_number = FieldTrial::kDefaultGroupNumber;
// Check if the field trial has already been created in some other way.
FieldTrial* existing_trial = Find(trial_name);
if (existing_trial) {
CHECK(existing_trial->forced_);
// If the default group name differs between the existing forced trial
// and this trial, then use a different value for the default group number.
if (default_group_number &&
default_group_name != existing_trial->default_group_name()) {
// If the new default group number corresponds to the group that was
// chosen for the forced trial (which has been finalized when it was
// forced), then set the default group number to that.
if (default_group_name == existing_trial->group_name_internal()) {
*default_group_number = existing_trial->group_;
} else {
// Otherwise, use |kNonConflictingGroupNumber| (-2) for the default
// group number, so that it does not conflict with the |AppendGroup()|
// result for the chosen group.
const int kNonConflictingGroupNumber = -2;
static_assert(
kNonConflictingGroupNumber != FieldTrial::kDefaultGroupNumber,
"The 'non-conflicting' group number conflicts");
static_assert(kNonConflictingGroupNumber != FieldTrial::kNotFinalized,
"The 'non-conflicting' group number conflicts");
*default_group_number = kNonConflictingGroupNumber;
}
}
return existing_trial;
}
double entropy_value;
if (randomization_type == FieldTrial::ONE_TIME_RANDOMIZED) {
// If an override entropy provider is given, use it.
const FieldTrial::EntropyProvider* entropy_provider =
override_entropy_provider ? override_entropy_provider
: GetEntropyProviderForOneTimeRandomization();
CHECK(entropy_provider);
entropy_value = entropy_provider->GetEntropyForTrial(trial_name,
randomization_seed);
} else {
DCHECK_EQ(FieldTrial::SESSION_RANDOMIZED, randomization_type);
DCHECK_EQ(0U, randomization_seed);
entropy_value = RandDouble();
}
FieldTrial* field_trial = new FieldTrial(trial_name, total_probability,
default_group_name, entropy_value);
if (GetBuildTime() > CreateTimeFromParams(year, month, day_of_month))
field_trial->Disable();
FieldTrialList::Register(field_trial);
return field_trial;
}
// static
FieldTrial* FieldTrialList::Find(const std::string& trial_name) {
if (!global_)
return nullptr;
AutoLock auto_lock(global_->lock_);
return global_->PreLockedFind(trial_name);
}
// static
int FieldTrialList::FindValue(const std::string& trial_name) {
FieldTrial* field_trial = Find(trial_name);
if (field_trial)
return field_trial->group();
return FieldTrial::kNotFinalized;
}
// static
std::string FieldTrialList::FindFullName(const std::string& trial_name) {
FieldTrial* field_trial = Find(trial_name);
if (field_trial)
return field_trial->group_name();
return std::string();
}
// static
bool FieldTrialList::TrialExists(const std::string& trial_name) {
return Find(trial_name) != nullptr;
}
// static
bool FieldTrialList::IsTrialActive(const std::string& trial_name) {
FieldTrial* field_trial = Find(trial_name);
FieldTrial::ActiveGroup active_group;
return field_trial && field_trial->GetActiveGroup(&active_group);
}
// static
void FieldTrialList::StatesToString(std::string* output) {
FieldTrial::ActiveGroups active_groups;
GetActiveFieldTrialGroups(&active_groups);
for (FieldTrial::ActiveGroups::const_iterator it = active_groups.begin();
it != active_groups.end(); ++it) {
DCHECK_EQ(std::string::npos,
it->trial_name.find(kPersistentStringSeparator));
DCHECK_EQ(std::string::npos,
it->group_name.find(kPersistentStringSeparator));
output->append(it->trial_name);
output->append(1, kPersistentStringSeparator);
output->append(it->group_name);
output->append(1, kPersistentStringSeparator);
}
}
// static
void FieldTrialList::AllStatesToString(std::string* output) {
if (!global_)
return;
AutoLock auto_lock(global_->lock_);
for (const auto& registered : global_->registered_) {
FieldTrial::State trial;
if (!registered.second->GetStateWhileLocked(&trial))
continue;
DCHECK_EQ(std::string::npos,
trial.trial_name->find(kPersistentStringSeparator));
DCHECK_EQ(std::string::npos,
trial.group_name->find(kPersistentStringSeparator));
if (trial.activated)
output->append(1, kActivationMarker);
output->append(*trial.trial_name);
output->append(1, kPersistentStringSeparator);
output->append(*trial.group_name);
output->append(1, kPersistentStringSeparator);
}
}
// static
void FieldTrialList::GetActiveFieldTrialGroups(
FieldTrial::ActiveGroups* active_groups) {
DCHECK(active_groups->empty());
if (!global_)
return;
AutoLock auto_lock(global_->lock_);
for (RegistrationMap::iterator it = global_->registered_.begin();
it != global_->registered_.end(); ++it) {
FieldTrial::ActiveGroup active_group;
if (it->second->GetActiveGroup(&active_group))
active_groups->push_back(active_group);
}
}
// static
void FieldTrialList::GetActiveFieldTrialGroupsFromString(
const std::string& trials_string,
FieldTrial::ActiveGroups* active_groups) {
std::vector<FieldTrialStringEntry> entries;
if (!ParseFieldTrialsString(trials_string, &entries))
return;
for (const auto& entry : entries) {
if (entry.activated) {
FieldTrial::ActiveGroup group;
group.trial_name = entry.trial_name.as_string();
group.group_name = entry.group_name.as_string();
active_groups->push_back(group);
}
}
}
// static
void FieldTrialList::GetInitiallyActiveFieldTrials(
const base::CommandLine& command_line,
FieldTrial::ActiveGroups* active_groups) {
DCHECK(global_);
DCHECK(global_->create_trials_from_command_line_called_);
if (!global_->field_trial_allocator_) {
GetActiveFieldTrialGroupsFromString(
command_line.GetSwitchValueASCII(switches::kForceFieldTrials),
active_groups);
return;
}
FieldTrialAllocator* allocator = global_->field_trial_allocator_.get();
FieldTrialAllocator::Iterator mem_iter(allocator);
const FieldTrial::FieldTrialEntry* entry;
while ((entry = mem_iter.GetNextOfObject<FieldTrial::FieldTrialEntry>()) !=
nullptr) {
StringPiece trial_name;
StringPiece group_name;
if (subtle::NoBarrier_Load(&entry->activated) &&
entry->GetTrialAndGroupName(&trial_name, &group_name)) {
FieldTrial::ActiveGroup group;
group.trial_name = trial_name.as_string();
group.group_name = group_name.as_string();
active_groups->push_back(group);
}
}
}
// static
bool FieldTrialList::CreateTrialsFromString(
const std::string& trials_string,
const std::set<std::string>& ignored_trial_names) {
DCHECK(global_);
if (trials_string.empty() || !global_)
return true;
std::vector<FieldTrialStringEntry> entries;
if (!ParseFieldTrialsString(trials_string, &entries))
return false;
for (const auto& entry : entries) {
const std::string trial_name = entry.trial_name.as_string();
const std::string group_name = entry.group_name.as_string();
if (ContainsKey(ignored_trial_names, trial_name))
continue;
FieldTrial* trial = CreateFieldTrial(trial_name, group_name);
if (!trial)
return false;
if (entry.activated) {
// Call |group()| to mark the trial as "used" and notify observers, if
// any. This is useful to ensure that field trials created in child
// processes are properly reported in crash reports.
trial->group();
}
}
return true;
}
// static
void FieldTrialList::CreateTrialsFromCommandLine(
const CommandLine& cmd_line,
const char* field_trial_handle_switch,
int fd_key) {
global_->create_trials_from_command_line_called_ = true;
#if defined(OS_WIN) || defined(OS_FUCHSIA)
if (cmd_line.HasSwitch(field_trial_handle_switch)) {
std::string switch_value =
cmd_line.GetSwitchValueASCII(field_trial_handle_switch);
bool result = CreateTrialsFromSwitchValue(switch_value);
DCHECK(result);
}
#elif defined(OS_POSIX) && !defined(OS_NACL)
// On POSIX, we check if the handle is valid by seeing if the browser process
// sent over the switch (we don't care about the value). Invalid handles
// occur in some browser tests which don't initialize the allocator.
if (cmd_line.HasSwitch(field_trial_handle_switch)) {
std::string switch_value =
cmd_line.GetSwitchValueASCII(field_trial_handle_switch);
bool result = CreateTrialsFromDescriptor(fd_key, switch_value);
DCHECK(result);
}
#endif
if (cmd_line.HasSwitch(switches::kForceFieldTrials)) {
bool result = FieldTrialList::CreateTrialsFromString(
cmd_line.GetSwitchValueASCII(switches::kForceFieldTrials),
std::set<std::string>());
DCHECK(result);
}
}
// static
void FieldTrialList::CreateFeaturesFromCommandLine(
const base::CommandLine& command_line,
const char* enable_features_switch,
const char* disable_features_switch,
FeatureList* feature_list) {
// Fallback to command line if not using shared memory.
if (!kUseSharedMemoryForFieldTrials ||
!global_->field_trial_allocator_.get()) {
return feature_list->InitializeFromCommandLine(
command_line.GetSwitchValueASCII(enable_features_switch),
command_line.GetSwitchValueASCII(disable_features_switch));
}
feature_list->InitializeFromSharedMemory(
global_->field_trial_allocator_.get());
}
#if defined(OS_WIN)
// static
void FieldTrialList::AppendFieldTrialHandleIfNeeded(
HandlesToInheritVector* handles) {
if (!global_)
return;
if (kUseSharedMemoryForFieldTrials) {
InstantiateFieldTrialAllocatorIfNeeded();
if (global_->readonly_allocator_handle_.IsValid())
handles->push_back(global_->readonly_allocator_handle_.GetHandle());
}
}
#elif defined(OS_FUCHSIA)
// TODO(fuchsia): Implement shared-memory configuration (crbug.com/752368).
#elif defined(OS_POSIX) && !defined(OS_NACL)
// static
SharedMemoryHandle FieldTrialList::GetFieldTrialHandle() {
if (global_ && kUseSharedMemoryForFieldTrials) {
InstantiateFieldTrialAllocatorIfNeeded();
// We check for an invalid handle where this gets called.
return global_->readonly_allocator_handle_;
}
return SharedMemoryHandle();
}
#endif
// static
void FieldTrialList::CopyFieldTrialStateToFlags(
const char* field_trial_handle_switch,
const char* enable_features_switch,
const char* disable_features_switch,
CommandLine* cmd_line) {
// TODO(lawrencewu): Ideally, having the global would be guaranteed. However,
// content browser tests currently don't create a FieldTrialList because they
// don't run ChromeBrowserMainParts code where it's done for Chrome.
// Some tests depend on the enable and disable features flag switch, though,
// so we can still add those even though AllStatesToString() will be a no-op.
if (!global_) {
AddFeatureAndFieldTrialFlags(enable_features_switch,
disable_features_switch, cmd_line);
return;
}
// Use shared memory to pass the state if the feature is enabled, otherwise
// fallback to passing it via the command line as a string.
if (kUseSharedMemoryForFieldTrials) {
InstantiateFieldTrialAllocatorIfNeeded();
// If the readonly handle didn't get duplicated properly, then fallback to
// original behavior.
if (!global_->readonly_allocator_handle_.IsValid()) {
AddFeatureAndFieldTrialFlags(enable_features_switch,
disable_features_switch, cmd_line);
return;
}
global_->field_trial_allocator_->UpdateTrackingHistograms();
std::string switch_value = SerializeSharedMemoryHandleMetadata(
global_->readonly_allocator_handle_);
cmd_line->AppendSwitchASCII(field_trial_handle_switch, switch_value);
return;
}
AddFeatureAndFieldTrialFlags(enable_features_switch, disable_features_switch,
cmd_line);
}
// static
FieldTrial* FieldTrialList::CreateFieldTrial(
const std::string& name,
const std::string& group_name) {
DCHECK(global_);
DCHECK_GE(name.size(), 0u);
DCHECK_GE(group_name.size(), 0u);
if (name.empty() || group_name.empty() || !global_)
return nullptr;
FieldTrial* field_trial = FieldTrialList::Find(name);
if (field_trial) {
// In single process mode, or when we force them from the command line,
// we may have already created the field trial.
if (field_trial->group_name_internal() != group_name)
return nullptr;
return field_trial;
}
const int kTotalProbability = 100;
field_trial = new FieldTrial(name, kTotalProbability, group_name, 0);
FieldTrialList::Register(field_trial);
// Force the trial, which will also finalize the group choice.
field_trial->SetForced();
return field_trial;
}
// static
void FieldTrialList::AddObserver(Observer* observer) {
if (!global_)
return;
global_->observer_list_->AddObserver(observer);
}
// static
void FieldTrialList::RemoveObserver(Observer* observer) {
if (!global_)
return;
global_->observer_list_->RemoveObserver(observer);
}
// static
void FieldTrialList::OnGroupFinalized(bool is_locked, FieldTrial* field_trial) {
if (!global_)
return;
if (is_locked) {
AddToAllocatorWhileLocked(global_->field_trial_allocator_.get(),
field_trial);
} else {
AutoLock auto_lock(global_->lock_);
AddToAllocatorWhileLocked(global_->field_trial_allocator_.get(),
field_trial);
}
}
// static
void FieldTrialList::NotifyFieldTrialGroupSelection(FieldTrial* field_trial) {
if (!global_)
return;
{
AutoLock auto_lock(global_->lock_);
if (field_trial->group_reported_)
return;
field_trial->group_reported_ = true;
if (!field_trial->enable_field_trial_)
return;
if (kUseSharedMemoryForFieldTrials)
ActivateFieldTrialEntryWhileLocked(field_trial);
}
// Recording for stability debugging has to be done inline as a task posted
// to an observer may not get executed before a crash.
base::debug::GlobalActivityTracker* tracker =
base::debug::GlobalActivityTracker::Get();
if (tracker) {
tracker->RecordFieldTrial(field_trial->trial_name(),
field_trial->group_name_internal());
}
global_->observer_list_->Notify(
FROM_HERE, &FieldTrialList::Observer::OnFieldTrialGroupFinalized,
field_trial->trial_name(), field_trial->group_name_internal());
}
// static
size_t FieldTrialList::GetFieldTrialCount() {
if (!global_)
return 0;
AutoLock auto_lock(global_->lock_);
return global_->registered_.size();
}
// static
bool FieldTrialList::GetParamsFromSharedMemory(
FieldTrial* field_trial,
std::map<std::string, std::string>* params) {
DCHECK(global_);
// If the field trial allocator is not set up yet, then there are several
// cases:
// - We are in the browser process and the allocator has not been set up
// yet. If we got here, then we couldn't find the params in
// FieldTrialParamAssociator, so it's definitely not here. Return false.
// - Using shared memory for field trials is not enabled. If we got here,
// then there's nothing in shared memory. Return false.
// - We are in the child process and the allocator has not been set up yet.
// If this is the case, then you are calling this too early. The field trial
// allocator should get set up very early in the lifecycle. Try to see if
// you can call it after it's been set up.
AutoLock auto_lock(global_->lock_);