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// Copyright 2014 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.
#ifndef COMPONENTS_VARIATIONS_VARIATIONS_HTTP_HEADER_PROVIDER_H_
#define COMPONENTS_VARIATIONS_VARIATIONS_HTTP_HEADER_PROVIDER_H_
#include <set>
#include <string>
#include <vector>
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/metrics/field_trial.h"
#include "base/synchronization/lock.h"
#include "components/variations/synthetic_trials.h"
#include "components/variations/variations_associated_data.h"
namespace base {
template <typename T>
struct DefaultSingletonTraits;
}
namespace variations {
// A helper class for maintaining client experiments and metrics state
// transmitted in custom HTTP request headers.
// This class is a thread-safe singleton.
class VariationsHttpHeaderProvider : public base::FieldTrialList::Observer,
public SyntheticTrialObserver {
public:
static VariationsHttpHeaderProvider* GetInstance();
// Returns the value of the client data header, computing and caching it if
// necessary.
std::string GetClientDataHeader();
// Returns a space-separated string containing the list of current active
// variations (as would be reported in the |variation_id| repeated field of
// the ClientVariations proto). The returned string is guaranteed to have a
// a leading and trailing space, e.g. " 123 234 345 ".
std::string GetVariationsString();
// Sets *additional* variation ids and trigger variation ids to be encoded in
// the X-Client-Data request header. This is intended for development use to
// force a server side experiment id. |variation_ids| should be a
// comma-separated string of numeric experiment ids. If an id is prefixed
// with "t" it will be treated as a trigger experiment id.
bool SetDefaultVariationIds(const std::string& variation_ids);
// Resets any cached state for tests.
void ResetForTesting();
private:
friend struct base::DefaultSingletonTraits<VariationsHttpHeaderProvider>;
FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
SetDefaultVariationIds_Valid);
FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
SetDefaultVariationIds_Invalid);
FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
OnFieldTrialGroupFinalized);
FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
GetVariationsString);
VariationsHttpHeaderProvider();
~VariationsHttpHeaderProvider() override;
// base::FieldTrialList::Observer:
// This will add the variation ID associated with |trial_name| and
// |group_name| to the variation ID cache.
void OnFieldTrialGroupFinalized(const std::string& trial_name,
const std::string& group_name) override;
// metrics::SyntheticTrialObserver:
void OnSyntheticTrialsChanged(
const std::vector<SyntheticTrialGroup>& groups) override;
// Prepares the variation IDs cache with initial values if not already done.
// This method also registers the caller with the FieldTrialList to receive
// new variation IDs.
void InitVariationIDsCacheIfNeeded();
// Takes whatever is currently in |variation_ids_set_| and recreates
// |variation_ids_header_| with it. Assumes the the |lock_| is currently
// held.
void UpdateVariationIDsHeaderValue();
// Returns the currently active set of variation ids, which includes any
// default values, synthetic variations and actual field trial variations.
std::set<VariationID> GetAllVariationIds();
// Guards |variation_ids_cache_initialized_|, |variation_ids_set_| and
// |variation_ids_header_|.
base::Lock lock_;
// Whether or not we've initialized the cache.
bool variation_ids_cache_initialized_;
// Keep a cache of variation IDs that are transmitted in headers to Google.
// This consists of a list of valid IDs, and the actual transmitted header.
std::set<VariationID> variation_ids_set_;
std::set<VariationID> variation_trigger_ids_set_;
// Provides the google experiment ids forced from command line.
std::set<VariationID> default_variation_ids_set_;
std::set<VariationID> default_trigger_id_set_;
// Variations ids from synthetic field trials.
std::set<VariationID> synthetic_variation_ids_set_;
std::string variation_ids_header_;
DISALLOW_COPY_AND_ASSIGN(VariationsHttpHeaderProvider);
};
} // namespace variations
#endif // COMPONENTS_VARIATIONS_VARIATIONS_HTTP_HEADER_PROVIDER_H_
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