chrome/browser/budget_service/budget_database.cc - chromium/src - Git at Google

 // Copyright 2016 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 "chrome/browser/budget_service/budget_database.h"

 #include "base/metrics/histogram_macros.h"
 #include "base/time/clock.h"
 #include "base/time/default_clock.h"
 #include "chrome/browser/budget_service/budget.pb.h"
 #include "chrome/browser/engagement/site_engagement_score.h"
 #include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/leveldb_proto/proto_database_impl.h"
 #include "content/public/browser/browser_thread.h"
 #include "url/gurl.h"
 #include "url/origin.h"

 using content::BrowserThread;

 namespace {

 // UMA are logged for the database with this string as part of the name.
 // They will be LevelDB.*.BudgetManager. Changes here should be synchronized
 // with histograms.xml.
 const char kDatabaseUMAName[] = "BudgetManager";

 // The default amount of time during which a budget will be valid.
 // This is 4 days = 96 hours.
 constexpr double kBudgetDurationInHours = 96;

 }  // namespace

 BudgetDatabase::BudgetInfo::BudgetInfo() {}

 BudgetDatabase::BudgetInfo::BudgetInfo(const BudgetInfo&& other)
     : last_engagement_award(other.last_engagement_award) {
   chunks = std::move(other.chunks);
 }

 BudgetDatabase::BudgetInfo::~BudgetInfo() {}

 BudgetDatabase::BudgetDatabase(
     Profile* profile,
     const base::FilePath& database_dir,
     const scoped_refptr<base::SequencedTaskRunner>& task_runner)
     : profile_(profile),
       db_(new leveldb_proto::ProtoDatabaseImpl<budget_service::Budget>(
           task_runner)),
       clock_(base::WrapUnique(new base::DefaultClock)),
       weak_ptr_factory_(this) {
   db_->Init(kDatabaseUMAName, database_dir,
             base::Bind(&BudgetDatabase::OnDatabaseInit,
                        weak_ptr_factory_.GetWeakPtr()));
 }

 BudgetDatabase::~BudgetDatabase() {}

 void BudgetDatabase::GetBudgetDetails(const url::Origin& origin,
                                       const GetBudgetCallback& callback) {
   SyncCache(origin,
             base::Bind(&BudgetDatabase::GetBudgetAfterSync,
                        weak_ptr_factory_.GetWeakPtr(), origin, callback));
 }

 void BudgetDatabase::SpendBudget(const url::Origin& origin,
                                  double amount,
                                  const SpendBudgetCallback& callback) {
   SyncCache(origin, base::Bind(&BudgetDatabase::SpendBudgetAfterSync,
                                weak_ptr_factory_.GetWeakPtr(), origin, amount,
                                callback));
 }

 void BudgetDatabase::SetClockForTesting(std::unique_ptr<base::Clock> clock) {
   clock_ = std::move(clock);
 }

 void BudgetDatabase::OnDatabaseInit(bool success) {
   // TODO(harkness): Consider caching the budget database now?
 }

 bool BudgetDatabase::IsCached(const url::Origin& origin) const {
   return budget_map_.find(origin) != budget_map_.end();
 }

 double BudgetDatabase::GetBudget(const url::Origin& origin) const {
   double total = 0;
   auto iter = budget_map_.find(origin);
   if (iter == budget_map_.end())
     return total;

   const BudgetInfo& info = iter->second;
   for (const BudgetChunk& chunk : info.chunks)
     total += chunk.amount;
   return total;
 }

 void BudgetDatabase::AddToCache(
     const url::Origin& origin,
     const CacheCallback& callback,
     bool success,
     std::unique_ptr<budget_service::Budget> budget_proto) {
   // If the database read failed or there's nothing to add, just return.
   if (!success || !budget_proto) {
     callback.Run(success);
     return;
   }

   // If there were two simultaneous loads, don't overwrite the cache value,
   // which might have been updated after the previous load.
   if (IsCached(origin)) {
     callback.Run(success);
     return;
   }

   // Add the data to the cache, converting from the proto format to an STL
   // format which is better for removing things from the list.
   BudgetInfo& info = budget_map_[origin];
   for (const auto& chunk : budget_proto->budget()) {
     info.chunks.emplace_back(chunk.amount(),
                              base::Time::FromInternalValue(chunk.expiration()));
   }

   info.last_engagement_award =
       base::Time::FromInternalValue(budget_proto->engagement_last_updated());

   callback.Run(success);
 }

 void BudgetDatabase::GetBudgetAfterSync(const url::Origin& origin,
                                         const GetBudgetCallback& callback,
                                         bool success) {
   mojo::Array<blink::mojom::BudgetStatePtr> predictions;

   // If the database wasn't able to read the information, return the
   // failure and an empty predictions array.
   if (!success) {
     callback.Run(blink::mojom::BudgetServiceErrorType::DATABASE_ERROR,
                  std::move(predictions));
     return;
   }

   // Now, build up the BudgetExpection. This is different from the format
   // in which the cache stores the data. The cache stores chunks of budget and
   // when that budget expires. The mojo array describes a set of times
   // and the budget at those times.
   double total = GetBudget(origin);

   // Always add one entry at the front of the list for the total budget now.
   blink::mojom::BudgetStatePtr prediction(blink::mojom::BudgetState::New());
   prediction->budget_at = total;
   prediction->time = clock_->Now().ToDoubleT();
   predictions.push_back(std::move(prediction));

   // Starting with the soonest expiring chunks, add entries for the
   // expiration times going forward.
   const BudgetChunks& chunks = budget_map_[origin].chunks;
   for (const auto& chunk : chunks) {
     blink::mojom::BudgetStatePtr prediction(blink::mojom::BudgetState::New());
     total -= chunk.amount;
     prediction->budget_at = total;
     prediction->time = chunk.expiration.ToDoubleT();
     predictions.push_back(std::move(prediction));
   }

   DCHECK_EQ(0, total);

   callback.Run(blink::mojom::BudgetServiceErrorType::NONE,
                std::move(predictions));
 }

 void BudgetDatabase::SpendBudgetAfterSync(const url::Origin& origin,
                                           double amount,
                                           const SpendBudgetCallback& callback,
                                           bool success) {
   if (!success) {
     callback.Run(blink::mojom::BudgetServiceErrorType::DATABASE_ERROR,
                  false /* success */);
     return;
   }

   // Get the current SES score, to generate UMA.
   SiteEngagementService* service = SiteEngagementService::Get(profile_);
   double score = service->GetScore(origin.GetURL());

   // Walk the list of budget chunks to see if the origin has enough budget.
   double total = 0;
   BudgetInfo& info = budget_map_[origin];
   for (const BudgetChunk& chunk : info.chunks)
     total += chunk.amount;

   if (total < amount) {
     UMA_HISTOGRAM_COUNTS_100("PushMessaging.SESForNoBudgetOrigin", score);
     callback.Run(blink::mojom::BudgetServiceErrorType::NONE,
                  false /* success */);
     return;
   } else if (total < amount * 2) {
     UMA_HISTOGRAM_COUNTS_100("PushMessaging.SESForLowBudgetOrigin", score);
   }

   // Walk the chunks and remove enough budget to cover the needed amount.
   double bill = amount;
   for (auto iter = info.chunks.begin(); iter != info.chunks.end();) {
     if (iter->amount > bill) {
       iter->amount -= bill;
       bill = 0;
       break;
     }
     bill -= iter->amount;
     iter = info.chunks.erase(iter);
   }

   // There should have been enough budget to cover the entire bill.
   DCHECK_EQ(0, bill);

   // Now that the cache is updated, write the data to the database.
   WriteCachedValuesToDatabase(
       origin, base::Bind(&BudgetDatabase::SpendBudgetAfterWrite,
                          weak_ptr_factory_.GetWeakPtr(), callback));
 }

 // This converts the bool value which is returned from the database to a Mojo
 // error type.
 void BudgetDatabase::SpendBudgetAfterWrite(const SpendBudgetCallback& callback,
                                            bool write_successful) {
   // TODO(harkness): If the database write fails, the cache will be out of sync
   // with the database. Consider ways to mitigate this.
   if (!write_successful) {
     callback.Run(blink::mojom::BudgetServiceErrorType::DATABASE_ERROR,
                  false /* success */);
     return;
   }
   callback.Run(blink::mojom::BudgetServiceErrorType::NONE, true /* success */);
 }

 void BudgetDatabase::WriteCachedValuesToDatabase(
     const url::Origin& origin,
     const StoreBudgetCallback& callback) {
   // Create the data structures that are passed to the ProtoDatabase.
   std::unique_ptr<
       leveldb_proto::ProtoDatabase<budget_service::Budget>::KeyEntryVector>
       entries(new leveldb_proto::ProtoDatabase<
               budget_service::Budget>::KeyEntryVector());
   std::unique_ptr<std::vector<std::string>> keys_to_remove(
       new std::vector<std::string>());

   // Each operation can either update the existing budget or remove the origin's
   // budget information.
   if (IsCached(origin)) {
     // Build the Budget proto object.
     budget_service::Budget budget;
     const BudgetInfo& info = budget_map_[origin];
     for (const auto& chunk : info.chunks) {
       budget_service::BudgetChunk* budget_chunk = budget.add_budget();
       budget_chunk->set_amount(chunk.amount);
       budget_chunk->set_expiration(chunk.expiration.ToInternalValue());
     }
     budget.set_engagement_last_updated(
         info.last_engagement_award.ToInternalValue());
     entries->push_back(std::make_pair(origin.Serialize(), budget));
   } else {
     // If the origin doesn't exist in the cache, this is a remove operation.
     keys_to_remove->push_back(origin.Serialize());
   }

   // Send the updates to the database.
   db_->UpdateEntries(std::move(entries), std::move(keys_to_remove), callback);
 }

 void BudgetDatabase::SyncCache(const url::Origin& origin,
                                const CacheCallback& callback) {
   // If the origin isn't already cached, add it to the cache.
   if (!IsCached(origin)) {
     CacheCallback add_callback =
         base::Bind(&BudgetDatabase::SyncLoadedCache,
                    weak_ptr_factory_.GetWeakPtr(), origin, callback);
     db_->GetEntry(origin.Serialize(), base::Bind(&BudgetDatabase::AddToCache,
                                                  weak_ptr_factory_.GetWeakPtr(),
                                                  origin, add_callback));
     return;
   }
   SyncLoadedCache(origin, callback, true /* success */);
 }

 void BudgetDatabase::SyncLoadedCache(const url::Origin& origin,
                                      const CacheCallback& callback,
                                      bool success) {
   if (!success) {
     callback.Run(false /* success */);
     return;
   }

   // Now, cleanup any expired budget chunks for the origin.
   bool needs_write = CleanupExpiredBudget(origin);

   // Get the SES score and add engagement budget for the site.
   AddEngagementBudget(origin);

   if (needs_write)
     WriteCachedValuesToDatabase(origin, callback);
   else
     callback.Run(success);
 }

 void BudgetDatabase::AddEngagementBudget(const url::Origin& origin) {
   // Get the current SES score, which we'll use to set a new budget.
   SiteEngagementService* service = SiteEngagementService::Get(profile_);
   double score = service->GetScore(origin.GetURL());

   // By default we award the "full" award. Then that ratio is decreased if
   // there have been other awards recently.
   double ratio = 1.0;

   // Calculate how much budget should be awarded. If there is no entry in the
   // cache then we award a full amount.
   if (IsCached(origin)) {
     base::TimeDelta elapsed =
         clock_->Now() - budget_map_[origin].last_engagement_award;
     int elapsed_hours = elapsed.InHours();
     // Don't give engagement awards for periods less than an hour.
     if (elapsed_hours < 1)
       return;
     if (elapsed_hours < kBudgetDurationInHours)
       ratio = elapsed_hours / kBudgetDurationInHours;
   }

   // Update the last_engagement_award to the current time. If the origin wasn't
   // already in the map, this adds a new entry for it.
   budget_map_[origin].last_engagement_award = clock_->Now();

   // Add a new chunk of budget for the origin at the default expiration time.
   base::Time expiration =
       clock_->Now() + base::TimeDelta::FromHours(kBudgetDurationInHours);
   budget_map_[origin].chunks.emplace_back(ratio * score, expiration);

   // Any time we award engagement budget, which is done at most once an hour
   // whenever any budget action is taken, record the budget.
   double budget = GetBudget(origin);
   UMA_HISTOGRAM_COUNTS_100("PushMessaging.BackgroundBudget", budget);
 }

 // Cleans up budget in the cache. Relies on the caller eventually writing the
 // cache back to the database.
 bool BudgetDatabase::CleanupExpiredBudget(const url::Origin& origin) {
   if (!IsCached(origin))
     return false;

   base::Time now = clock_->Now();
   BudgetChunks& chunks = budget_map_[origin].chunks;
   auto cleanup_iter = chunks.begin();

   // This relies on the list of chunks being in timestamp order.
   while (cleanup_iter != chunks.end() && cleanup_iter->expiration <= now)
     cleanup_iter = chunks.erase(cleanup_iter);

   // If the entire budget is empty now AND there have been no engagements
   // in the last kBudgetDurationInHours hours, remove this from the cache.
   if (chunks.empty() &&
       budget_map_[origin].last_engagement_award <
           clock_->Now() - base::TimeDelta::FromHours(kBudgetDurationInHours)) {
     budget_map_.erase(origin);
     return true;
   }

   // Although some things may have expired, there are some chunks still valid.
   // Don't write to the DB now, write either when all chunks expire or when the
   // origin spends some budget.
   return false;
 }
	// Copyright 2016 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 "chrome/browser/budget_service/budget_database.h"

	#include "base/metrics/histogram_macros.h"
	#include "base/time/clock.h"
	#include "base/time/default_clock.h"
	#include "chrome/browser/budget_service/budget.pb.h"
	#include "chrome/browser/engagement/site_engagement_score.h"
	#include "chrome/browser/engagement/site_engagement_service.h"
	#include "chrome/browser/profiles/profile.h"
	#include "components/leveldb_proto/proto_database_impl.h"
	#include "content/public/browser/browser_thread.h"
	#include "url/gurl.h"
	#include "url/origin.h"

	using content::BrowserThread;

	namespace {

	// UMA are logged for the database with this string as part of the name.
	// They will be LevelDB.*.BudgetManager. Changes here should be synchronized
	// with histograms.xml.
	const char kDatabaseUMAName[] = "BudgetManager";

	// The default amount of time during which a budget will be valid.
	// This is 4 days = 96 hours.
	constexpr double kBudgetDurationInHours = 96;

	} // namespace

	BudgetDatabase::BudgetInfo::BudgetInfo() {}

	BudgetDatabase::BudgetInfo::BudgetInfo(const BudgetInfo&& other)
	: last_engagement_award(other.last_engagement_award) {
	chunks = std::move(other.chunks);
	}

	BudgetDatabase::BudgetInfo::~BudgetInfo() {}

	BudgetDatabase::BudgetDatabase(
	Profile* profile,
	const base::FilePath& database_dir,
	const scoped_refptr<base::SequencedTaskRunner>& task_runner)
	: profile_(profile),
	db_(new leveldb_proto::ProtoDatabaseImpl<budget_service::Budget>(
	task_runner)),
	clock_(base::WrapUnique(new base::DefaultClock)),
	weak_ptr_factory_(this) {
	db_->Init(kDatabaseUMAName, database_dir,
	base::Bind(&BudgetDatabase::OnDatabaseInit,
	weak_ptr_factory_.GetWeakPtr()));
	}

	BudgetDatabase::~BudgetDatabase() {}

	void BudgetDatabase::GetBudgetDetails(const url::Origin& origin,
	const GetBudgetCallback& callback) {
	SyncCache(origin,
	base::Bind(&BudgetDatabase::GetBudgetAfterSync,
	weak_ptr_factory_.GetWeakPtr(), origin, callback));
	}

	void BudgetDatabase::SpendBudget(const url::Origin& origin,
	double amount,
	const SpendBudgetCallback& callback) {
	SyncCache(origin, base::Bind(&BudgetDatabase::SpendBudgetAfterSync,
	weak_ptr_factory_.GetWeakPtr(), origin, amount,
	callback));
	}

	void BudgetDatabase::SetClockForTesting(std::unique_ptr<base::Clock> clock) {
	clock_ = std::move(clock);
	}

	void BudgetDatabase::OnDatabaseInit(bool success) {
	// TODO(harkness): Consider caching the budget database now?
	}

	bool BudgetDatabase::IsCached(const url::Origin& origin) const {
	return budget_map_.find(origin) != budget_map_.end();
	}

	double BudgetDatabase::GetBudget(const url::Origin& origin) const {
	double total = 0;
	auto iter = budget_map_.find(origin);
	if (iter == budget_map_.end())
	return total;

	const BudgetInfo& info = iter->second;
	for (const BudgetChunk& chunk : info.chunks)
	total += chunk.amount;
	return total;
	}

	void BudgetDatabase::AddToCache(
	const url::Origin& origin,
	const CacheCallback& callback,
	bool success,
	std::unique_ptr<budget_service::Budget> budget_proto) {
	// If the database read failed or there's nothing to add, just return.
	if (!success \|\| !budget_proto) {
	callback.Run(success);
	return;
	}

	// If there were two simultaneous loads, don't overwrite the cache value,
	// which might have been updated after the previous load.
	if (IsCached(origin)) {
	callback.Run(success);
	return;
	}

	// Add the data to the cache, converting from the proto format to an STL
	// format which is better for removing things from the list.
	BudgetInfo& info = budget_map_[origin];
	for (const auto& chunk : budget_proto->budget()) {
	info.chunks.emplace_back(chunk.amount(),
	base::Time::FromInternalValue(chunk.expiration()));
	}

	info.last_engagement_award =
	base::Time::FromInternalValue(budget_proto->engagement_last_updated());

	callback.Run(success);
	}

	void BudgetDatabase::GetBudgetAfterSync(const url::Origin& origin,
	const GetBudgetCallback& callback,
	bool success) {
	mojo::Array<blink::mojom::BudgetStatePtr> predictions;

	// If the database wasn't able to read the information, return the
	// failure and an empty predictions array.
	if (!success) {
	callback.Run(blink::mojom::BudgetServiceErrorType::DATABASE_ERROR,
	std::move(predictions));
	return;
	}

	// Now, build up the BudgetExpection. This is different from the format
	// in which the cache stores the data. The cache stores chunks of budget and
	// when that budget expires. The mojo array describes a set of times
	// and the budget at those times.
	double total = GetBudget(origin);

	// Always add one entry at the front of the list for the total budget now.
	blink::mojom::BudgetStatePtr prediction(blink::mojom::BudgetState::New());
	prediction->budget_at = total;
	prediction->time = clock_->Now().ToDoubleT();
	predictions.push_back(std::move(prediction));

	// Starting with the soonest expiring chunks, add entries for the
	// expiration times going forward.
	const BudgetChunks& chunks = budget_map_[origin].chunks;
	for (const auto& chunk : chunks) {
	blink::mojom::BudgetStatePtr prediction(blink::mojom::BudgetState::New());
	total -= chunk.amount;
	prediction->budget_at = total;
	prediction->time = chunk.expiration.ToDoubleT();
	predictions.push_back(std::move(prediction));
	}

	DCHECK_EQ(0, total);

	callback.Run(blink::mojom::BudgetServiceErrorType::NONE,
	std::move(predictions));
	}

	void BudgetDatabase::SpendBudgetAfterSync(const url::Origin& origin,
	double amount,
	const SpendBudgetCallback& callback,
	bool success) {
	if (!success) {
	callback.Run(blink::mojom::BudgetServiceErrorType::DATABASE_ERROR,
	false /* success */);
	return;
	}

	// Get the current SES score, to generate UMA.
	SiteEngagementService* service = SiteEngagementService::Get(profile_);
	double score = service->GetScore(origin.GetURL());

	// Walk the list of budget chunks to see if the origin has enough budget.
	double total = 0;
	BudgetInfo& info = budget_map_[origin];
	for (const BudgetChunk& chunk : info.chunks)
	total += chunk.amount;

	if (total < amount) {
	UMA_HISTOGRAM_COUNTS_100("PushMessaging.SESForNoBudgetOrigin", score);
	callback.Run(blink::mojom::BudgetServiceErrorType::NONE,
	false /* success */);
	return;
	} else if (total < amount * 2) {
	UMA_HISTOGRAM_COUNTS_100("PushMessaging.SESForLowBudgetOrigin", score);
	}

	// Walk the chunks and remove enough budget to cover the needed amount.
	double bill = amount;
	for (auto iter = info.chunks.begin(); iter != info.chunks.end();) {
	if (iter->amount > bill) {
	iter->amount -= bill;
	bill = 0;
	break;
	}
	bill -= iter->amount;
	iter = info.chunks.erase(iter);
	}

	// There should have been enough budget to cover the entire bill.
	DCHECK_EQ(0, bill);

	// Now that the cache is updated, write the data to the database.
	WriteCachedValuesToDatabase(
	origin, base::Bind(&BudgetDatabase::SpendBudgetAfterWrite,
	weak_ptr_factory_.GetWeakPtr(), callback));
	}

	// This converts the bool value which is returned from the database to a Mojo
	// error type.
	void BudgetDatabase::SpendBudgetAfterWrite(const SpendBudgetCallback& callback,
	bool write_successful) {
	// TODO(harkness): If the database write fails, the cache will be out of sync
	// with the database. Consider ways to mitigate this.
	if (!write_successful) {
	callback.Run(blink::mojom::BudgetServiceErrorType::DATABASE_ERROR,
	false /* success */);
	return;
	}
	callback.Run(blink::mojom::BudgetServiceErrorType::NONE, true /* success */);
	}

	void BudgetDatabase::WriteCachedValuesToDatabase(
	const url::Origin& origin,
	const StoreBudgetCallback& callback) {
	// Create the data structures that are passed to the ProtoDatabase.
	std::unique_ptr<
	leveldb_proto::ProtoDatabase<budget_service::Budget>::KeyEntryVector>
	entries(new leveldb_proto::ProtoDatabase<
	budget_service::Budget>::KeyEntryVector());
	std::unique_ptr<std::vector<std::string>> keys_to_remove(
	new std::vector<std::string>());

	// Each operation can either update the existing budget or remove the origin's
	// budget information.
	if (IsCached(origin)) {
	// Build the Budget proto object.
	budget_service::Budget budget;
	const BudgetInfo& info = budget_map_[origin];
	for (const auto& chunk : info.chunks) {
	budget_service::BudgetChunk* budget_chunk = budget.add_budget();
	budget_chunk->set_amount(chunk.amount);
	budget_chunk->set_expiration(chunk.expiration.ToInternalValue());
	}
	budget.set_engagement_last_updated(
	info.last_engagement_award.ToInternalValue());
	entries->push_back(std::make_pair(origin.Serialize(), budget));
	} else {
	// If the origin doesn't exist in the cache, this is a remove operation.
	keys_to_remove->push_back(origin.Serialize());
	}

	// Send the updates to the database.
	db_->UpdateEntries(std::move(entries), std::move(keys_to_remove), callback);
	}

	void BudgetDatabase::SyncCache(const url::Origin& origin,
	const CacheCallback& callback) {
	// If the origin isn't already cached, add it to the cache.
	if (!IsCached(origin)) {
	CacheCallback add_callback =
	base::Bind(&BudgetDatabase::SyncLoadedCache,
	weak_ptr_factory_.GetWeakPtr(), origin, callback);
	db_->GetEntry(origin.Serialize(), base::Bind(&BudgetDatabase::AddToCache,
	weak_ptr_factory_.GetWeakPtr(),
	origin, add_callback));
	return;
	}
	SyncLoadedCache(origin, callback, true /* success */);
	}

	void BudgetDatabase::SyncLoadedCache(const url::Origin& origin,
	const CacheCallback& callback,
	bool success) {
	if (!success) {
	callback.Run(false /* success */);
	return;
	}

	// Now, cleanup any expired budget chunks for the origin.
	bool needs_write = CleanupExpiredBudget(origin);

	// Get the SES score and add engagement budget for the site.
	AddEngagementBudget(origin);

	if (needs_write)
	WriteCachedValuesToDatabase(origin, callback);
	else
	callback.Run(success);
	}

	void BudgetDatabase::AddEngagementBudget(const url::Origin& origin) {
	// Get the current SES score, which we'll use to set a new budget.
	SiteEngagementService* service = SiteEngagementService::Get(profile_);
	double score = service->GetScore(origin.GetURL());

	// By default we award the "full" award. Then that ratio is decreased if
	// there have been other awards recently.
	double ratio = 1.0;

	// Calculate how much budget should be awarded. If there is no entry in the
	// cache then we award a full amount.
	if (IsCached(origin)) {
	base::TimeDelta elapsed =
	clock_->Now() - budget_map_[origin].last_engagement_award;
	int elapsed_hours = elapsed.InHours();
	// Don't give engagement awards for periods less than an hour.
	if (elapsed_hours < 1)
	return;
	if (elapsed_hours < kBudgetDurationInHours)
	ratio = elapsed_hours / kBudgetDurationInHours;
	}

	// Update the last_engagement_award to the current time. If the origin wasn't
	// already in the map, this adds a new entry for it.
	budget_map_[origin].last_engagement_award = clock_->Now();

	// Add a new chunk of budget for the origin at the default expiration time.
	base::Time expiration =
	clock_->Now() + base::TimeDelta::FromHours(kBudgetDurationInHours);
	budget_map_[origin].chunks.emplace_back(ratio * score, expiration);

	// Any time we award engagement budget, which is done at most once an hour
	// whenever any budget action is taken, record the budget.
	double budget = GetBudget(origin);
	UMA_HISTOGRAM_COUNTS_100("PushMessaging.BackgroundBudget", budget);
	}

	// Cleans up budget in the cache. Relies on the caller eventually writing the
	// cache back to the database.
	bool BudgetDatabase::CleanupExpiredBudget(const url::Origin& origin) {
	if (!IsCached(origin))
	return false;

	base::Time now = clock_->Now();
	BudgetChunks& chunks = budget_map_[origin].chunks;
	auto cleanup_iter = chunks.begin();

	// This relies on the list of chunks being in timestamp order.
	while (cleanup_iter != chunks.end() && cleanup_iter->expiration <= now)
	cleanup_iter = chunks.erase(cleanup_iter);

	// If the entire budget is empty now AND there have been no engagements
	// in the last kBudgetDurationInHours hours, remove this from the cache.
	if (chunks.empty() &&
	budget_map_[origin].last_engagement_award <
	clock_->Now() - base::TimeDelta::FromHours(kBudgetDurationInHours)) {
	budget_map_.erase(origin);
	return true;
	}

	// Although some things may have expired, there are some chunks still valid.
	// Don't write to the DB now, write either when all chunks expire or when the
	// origin spends some budget.
	return false;
	}