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// Copyright 2020 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 "third_party/blink/common/privacy_budget/aggregating_sample_collector.h"
#include <type_traits>
#include <unordered_map>
#include <vector>
#include "base/check.h"
#include "base/compiler_specific.h"
#include "base/no_destructor.h"
#include "base/stl_util.h"
#include "base/synchronization/lock.h"
#include "base/template_util.h"
#include "base/time/time.h"
#include "services/metrics/public/cpp/ukm_builders.h"
#include "services/metrics/public/cpp/ukm_source_id.h"
#include "services/metrics/public/mojom/ukm_interface.mojom.h"
#include "third_party/blink/public/common/privacy_budget/identifiability_sample_collector.h"
#include "third_party/blink/public/common/privacy_budget/identifiability_study_settings.h"
#include "third_party/blink/public/common/privacy_budget/identifiable_sample.h"
namespace blink {
namespace internal {
// Per-process singleton.
AggregatingSampleCollector* GetCollectorInstance() {
static base::NoDestructor<AggregatingSampleCollector> impl;
return impl.get();
}
} // namespace internal
namespace {
bool IsStudyActive() {
return IdentifiabilityStudySettings::Get()->IsActive();
}
} // namespace
const unsigned AggregatingSampleCollector::kMaxTrackedSurfaces;
const unsigned AggregatingSampleCollector::kMaxTrackedSamplesPerSurface;
const unsigned AggregatingSampleCollector::kMaxUnsentSamples;
const unsigned AggregatingSampleCollector::kMaxUnsentSources;
const base::TimeDelta AggregatingSampleCollector::kMaxUnsentSampleAge;
AggregatingSampleCollector::AggregatingSampleCollector() = default;
AggregatingSampleCollector::~AggregatingSampleCollector() = default;
void AggregatingSampleCollector::Record(
ukm::UkmRecorder* recorder,
ukm::SourceId source,
std::vector<IdentifiableSample> samples) {
// recorder == nullptr or source == kInvalidSourceId can happen, for example,
// if metrics are being reported against an unsupported ExecutionContext type
// or for some reason the UkmRecorder or a valid source is unavailable.
if (!IsStudyActive() || !recorder || source == ukm::kInvalidSourceId)
return;
if (TryAcceptSamples(source, std::move(samples)))
Flush(recorder);
}
void AggregatingSampleCollector::Flush(ukm::UkmRecorder* recorder) {
if (!recorder)
return;
std::unordered_multimap<ukm::SourceId, UkmMetricsContainerType> unsent;
// Gratuitous block for releasing `lock_` after doing the minimal possible
// work.
{
base::AutoLock l(lock_);
if (unsent_sample_count_ == 0)
return;
unsent_metrics_.swap(unsent);
unsent_sample_count_ = 0;
}
for (auto& kv : unsent) {
auto entry = ukm::mojom::UkmEntry::New(
kv.first, ukm::builders::Identifiability::kEntryNameHash,
std::move(kv.second));
recorder->AddEntry(std::move(entry));
}
}
void AggregatingSampleCollector::FlushSource(ukm::UkmRecorder* recorder,
ukm::SourceId source) {
if (!IsStudyActive() || !recorder)
return;
std::vector<UkmMetricsContainerType> metric_sets;
{
base::AutoLock l(lock_);
if (unsent_sample_count_ == 0)
return;
if (unsent_metrics_.count(source) == 0)
return;
const auto bucket = unsent_metrics_.bucket(source);
for (auto it = unsent_metrics_.begin(bucket);
it != unsent_metrics_.end(bucket); ++it) {
if (it->first != source)
continue;
DCHECK_GE(unsent_sample_count_, it->second.size());
unsent_sample_count_ -= it->second.size();
metric_sets.emplace_back(std::move(it->second));
}
unsent_metrics_.erase(source);
}
for (auto& metric : metric_sets) {
auto entry = ukm::mojom::UkmEntry::New(
source, ukm::builders::Identifiability::kEntryNameHash,
std::move(metric));
recorder->AddEntry(std::move(entry));
}
}
void AggregatingSampleCollector::ResetForTesting() {
base::AutoLock l(lock_);
per_surface_samples_.clear();
unsent_metrics_.clear();
unsent_sample_count_ = 0;
}
bool AggregatingSampleCollector::TryAcceptSamples(
ukm::SourceId source,
std::vector<IdentifiableSample> samples) {
base::AutoLock l(lock_);
for (const auto& sample : samples)
TryAcceptSingleSample(source, sample);
// This check needs to happen regardless of whether any new samples could be
// accepted due to the max age check.
return unsent_sample_count_ > kMaxUnsentSamples ||
unsent_metrics_.size() > kMaxUnsentSources ||
(unsent_sample_count_ > 0 &&
base::TimeTicks::Now() - time_of_first_unsent_arrival_ >=
kMaxUnsentSampleAge);
}
void AggregatingSampleCollector::TryAcceptSingleSample(
ukm::SourceId new_source,
const IdentifiableSample& new_sample) {
auto samples_for_surface_it = per_surface_samples_.find(new_sample.surface);
if (samples_for_surface_it == per_surface_samples_.end()) {
// New surface, but can't add any more.
if (per_surface_samples_.size() >= kMaxTrackedSurfaces)
return;
per_surface_samples_.emplace(
new_sample.surface,
Samples{.samples = {{new_sample.value}}, .total_value_count = 1});
} else {
Samples& sample_set = samples_for_surface_it->second;
++sample_set.total_value_count;
// Already exists.
if (sample_set.samples.contains(new_sample.value))
return;
// Want to add one, but can't.
if (sample_set.samples.size() >= kMaxTrackedSamplesPerSurface) {
sample_set.overflowed = true;
return;
}
sample_set.samples.insert(new_sample.value);
}
AddNewUnsentSample(new_source, new_sample);
}
void AggregatingSampleCollector::AddNewUnsentSample(
ukm::SourceId source,
const IdentifiableSample& new_sample) {
const auto kNewKey = new_sample.surface.ToUkmMetricHash();
const auto kNewValue = new_sample.value.ToUkmMetricValue();
if (!AddNewUnsentSampleToKnownSource(source, kNewKey, kNewValue)) {
unsent_metrics_.emplace(source,
UkmMetricsContainerType({{kNewKey, kNewValue}}));
}
DCHECK_LE(unsent_metrics_.count(source), kMaxTrackedSamplesPerSurface);
++unsent_sample_count_;
// Age of the oldest sample determines the expiry of the entire list of unsent
// samples.
if (unsent_sample_count_ == 1)
time_of_first_unsent_arrival_ = base::TimeTicks::Now();
}
bool AggregatingSampleCollector::AddNewUnsentSampleToKnownSource(
ukm::SourceId source,
uint64_t key,
int64_t value) {
if (unsent_metrics_.bucket_count() == 0)
return false;
const auto kSourceBucket = unsent_metrics_.bucket(source);
for (auto metric_map_it = unsent_metrics_.begin(kSourceBucket);
metric_map_it != unsent_metrics_.end(kSourceBucket); ++metric_map_it) {
// There could be bucket collisions.
if (metric_map_it->first != source)
continue;
// result.second is true if the insertion was successful. I.e. `key` didn't
// exist before.
auto result = metric_map_it->second.try_emplace(key, value);
if (result.second)
return true;
}
return false;
}
} // namespace blink
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