statsd/src/anomaly/AnomalyTracker.cpp - platform/packages/modules/StatsD - Git at Google

 /*
  * Copyright (C) 2017 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #define STATSD_DEBUG false  // STOPSHIP if true
 #include "Log.h"

 #include "AnomalyTracker.h"
 #include "external/Perfetto.h"
 #include "guardrail/StatsdStats.h"
 #include "metadata_util.h"
 #include "stats_log_util.h"
 #include "subscriber_util.h"
 #include "subscriber/IncidentdReporter.h"
 #include "subscriber/SubscriberReporter.h"

 #include <inttypes.h>
 #include <statslog_statsd.h>
 #include <time.h>

 namespace android {
 namespace os {
 namespace statsd {

 AnomalyTracker::AnomalyTracker(const Alert& alert, const ConfigKey& configKey)
         : mAlert(alert), mConfigKey(configKey), mNumOfPastBuckets(mAlert.num_buckets() - 1) {
     VLOG("AnomalyTracker() called");
     resetStorage();  // initialization
 }

 AnomalyTracker::~AnomalyTracker() {
     VLOG("~AnomalyTracker() called");
 }

 void AnomalyTracker::onConfigUpdated() {
     mSubscriptions.clear();
 }

 void AnomalyTracker::resetStorage() {
     VLOG("resetStorage() called.");
     mPastBuckets.clear();
     // Excludes the current bucket.
     mPastBuckets.resize(mNumOfPastBuckets);
     mSumOverPastBuckets.clear();
 }

 size_t AnomalyTracker::index(int64_t bucketNum) const {
     if (bucketNum < 0) {
         ALOGE("index() was passed a negative bucket number (%lld)!", (long long)bucketNum);
     }
     return bucketNum % mNumOfPastBuckets;
 }

 void AnomalyTracker::advanceMostRecentBucketTo(const int64_t& bucketNum) {
     VLOG("advanceMostRecentBucketTo() called.");
     if (mNumOfPastBuckets <= 0) {
         return;
     }
     if (bucketNum <= mMostRecentBucketNum) {
         ALOGW("Cannot advance buckets backwards (bucketNum=%lld but mMostRecentBucketNum=%lld)",
               (long long)bucketNum, (long long)mMostRecentBucketNum);
         return;
     }
     // If in the future (i.e. buckets are ancient), just empty out all past info.
     if (bucketNum >= mMostRecentBucketNum + mNumOfPastBuckets) {
         resetStorage();
         mMostRecentBucketNum = bucketNum;
         return;
     }

     // Clear out space by emptying out old mPastBuckets[i] values and update mSumOverPastBuckets.
     for (int64_t i = mMostRecentBucketNum + 1; i <= bucketNum; i++) {
         const int idx = index(i);
         subtractBucketFromSum(mPastBuckets[idx]);
         mPastBuckets[idx] = nullptr;  // release (but not clear) the old bucket.
     }
     mMostRecentBucketNum = bucketNum;
 }

 void AnomalyTracker::addPastBucket(const MetricDimensionKey& key,
                                    const int64_t& bucketValue,
                                    const int64_t& bucketNum) {
     VLOG("addPastBucket(bucketValue) called.");
     if (mNumOfPastBuckets == 0 ||
         bucketNum < 0 || bucketNum <= mMostRecentBucketNum - mNumOfPastBuckets) {
         return;
     }

     const int bucketIndex = index(bucketNum);
     if (bucketNum <= mMostRecentBucketNum && (mPastBuckets[bucketIndex] != nullptr)) {
         // We need to insert into an already existing past bucket.
         std::shared_ptr<DimToValMap>& bucket = mPastBuckets[bucketIndex];
         auto itr = bucket->find(key);
         if (itr != bucket->end()) {
             // Old entry already exists; update it.
             subtractValueFromSum(key, itr->second);
             itr->second = bucketValue;
         } else {
             bucket->insert({key, bucketValue});
         }
         mSumOverPastBuckets[key] += bucketValue;
     } else {
         // Bucket does not exist yet (in future or was never made), so we must make it.
         std::shared_ptr<DimToValMap> bucket = std::make_shared<DimToValMap>();
         bucket->insert({key, bucketValue});
         addPastBucket(bucket, bucketNum);
     }
 }

 void AnomalyTracker::addPastBucket(std::shared_ptr<DimToValMap> bucket,
                                    const int64_t& bucketNum) {
     VLOG("addPastBucket(bucket) called.");
     if (mNumOfPastBuckets == 0 ||
             bucketNum < 0 || bucketNum <= mMostRecentBucketNum - mNumOfPastBuckets) {
         return;
     }

     if (bucketNum <= mMostRecentBucketNum) {
         // We are updating an old bucket, not adding a new one.
         subtractBucketFromSum(mPastBuckets[index(bucketNum)]);
     } else {
         // Clear space for the new bucket to be at bucketNum.
         advanceMostRecentBucketTo(bucketNum);
     }
     mPastBuckets[index(bucketNum)] = bucket;
     addBucketToSum(bucket);
 }

 void AnomalyTracker::subtractBucketFromSum(const shared_ptr<DimToValMap>& bucket) {
     if (bucket == nullptr) {
         return;
     }
     for (const auto& keyValuePair : *bucket) {
         subtractValueFromSum(keyValuePair.first, keyValuePair.second);
     }
 }


 void AnomalyTracker::subtractValueFromSum(const MetricDimensionKey& key,
                                           const int64_t& bucketValue) {
     auto itr = mSumOverPastBuckets.find(key);
     if (itr == mSumOverPastBuckets.end()) {
         return;
     }
     itr->second -= bucketValue;
     if (itr->second == 0) {
         mSumOverPastBuckets.erase(itr);
     }
 }

 void AnomalyTracker::addBucketToSum(const shared_ptr<DimToValMap>& bucket) {
     if (bucket == nullptr) {
         return;
     }
     // For each dimension present in the bucket, add its value to its corresponding sum.
     for (const auto& keyValuePair : *bucket) {
         mSumOverPastBuckets[keyValuePair.first] += keyValuePair.second;
     }
 }

 int64_t AnomalyTracker::getPastBucketValue(const MetricDimensionKey& key,
                                            const int64_t& bucketNum) const {
     if (bucketNum < 0 || mMostRecentBucketNum < 0
             || bucketNum <= mMostRecentBucketNum - mNumOfPastBuckets
             || bucketNum > mMostRecentBucketNum) {
         return 0;
     }

     const auto& bucket = mPastBuckets[index(bucketNum)];
     if (bucket == nullptr) {
         return 0;
     }
     const auto& itr = bucket->find(key);
     return itr == bucket->end() ? 0 : itr->second;
 }

 int64_t AnomalyTracker::getSumOverPastBuckets(const MetricDimensionKey& key) const {
     const auto& itr = mSumOverPastBuckets.find(key);
     if (itr != mSumOverPastBuckets.end()) {
         return itr->second;
     }
     return 0;
 }

 bool AnomalyTracker::detectAnomaly(const int64_t& currentBucketNum,
                                    const MetricDimensionKey& key,
                                    const int64_t& currentBucketValue) {

     // currentBucketNum should be the next bucket after pastBuckets. If not, advance so that it is.
     if (currentBucketNum > mMostRecentBucketNum + 1) {
         advanceMostRecentBucketTo(currentBucketNum - 1);
     }
     return mAlert.has_trigger_if_sum_gt() &&
            getSumOverPastBuckets(key) + currentBucketValue > mAlert.trigger_if_sum_gt();
 }

 void AnomalyTracker::declareAnomaly(const int64_t& timestampNs, int64_t metricId,
                                     const MetricDimensionKey& key, int64_t metricValue) {
     // TODO(b/110563466): Why receive timestamp? RefractoryPeriod should always be based on
     // real time right now.
     if (isInRefractoryPeriod(timestampNs, key)) {
         VLOG("Skipping anomaly declaration since within refractory period");
         return;
     }
     if (mAlert.has_refractory_period_secs()) {
         mRefractoryPeriodEndsSec[key] = ((timestampNs + NS_PER_SEC - 1) / NS_PER_SEC) // round up
                                         + mAlert.refractory_period_secs();
         // TODO(b/110563466): If we had access to the bucket_size_millis, consider
         // calling resetStorage()
         // if (mAlert.refractory_period_secs() > mNumOfPastBuckets * bucketSizeNs) {resetStorage();}
     }

     if (!mSubscriptions.empty()) {
         ALOGI("An anomaly (%" PRId64 ") %s has occurred! Informing subscribers.",
                 mAlert.id(), key.toString().c_str());
         informSubscribers(key, metricId, metricValue);
     } else {
         ALOGI("An anomaly has occurred! (But no subscriber for that alert.)");
     }

     StatsdStats::getInstance().noteAnomalyDeclared(mConfigKey, mAlert.id());

     // TODO(b/110564268): This should also take in the const MetricDimensionKey& key?
     util::stats_write(util::ANOMALY_DETECTED, mConfigKey.GetUid(),
                       mConfigKey.GetId(), mAlert.id());
 }

 void AnomalyTracker::detectAndDeclareAnomaly(const int64_t& timestampNs,
                                              const int64_t& currBucketNum, int64_t metricId,
                                              const MetricDimensionKey& key,
                                              const int64_t& currentBucketValue) {
     if (detectAnomaly(currBucketNum, key, currentBucketValue)) {
         declareAnomaly(timestampNs, metricId, key, currentBucketValue);
     }
 }

 bool AnomalyTracker::isInRefractoryPeriod(const int64_t& timestampNs,
                                           const MetricDimensionKey& key) const {
     const auto& it = mRefractoryPeriodEndsSec.find(key);
     if (it != mRefractoryPeriodEndsSec.end()) {
         return timestampNs < (it->second *  (int64_t)NS_PER_SEC);
     }
     return false;
 }

 std::pair<optional<InvalidConfigReason>, uint64_t> AnomalyTracker::getProtoHash() const {
     string serializedAlert;
     if (!mAlert.SerializeToString(&serializedAlert)) {
         ALOGW("Unable to serialize alert %lld", (long long)mAlert.id());
         return {createInvalidConfigReasonWithAlert(INVALID_CONFIG_REASON_ALERT_SERIALIZATION_FAILED,
                                                    mAlert.metric_id(), mAlert.id()),
                 0};
     }
     return {nullopt, Hash64(serializedAlert)};
 }

 void AnomalyTracker::informSubscribers(const MetricDimensionKey& key, int64_t metric_id,
                                        int64_t metricValue) {
     triggerSubscribers(mAlert.id(), metric_id, key, metricValue, mConfigKey, mSubscriptions);
 }

 bool AnomalyTracker::writeAlertMetadataToProto(int64_t currentWallClockTimeNs,
                                                int64_t systemElapsedTimeNs,
                                                metadata::AlertMetadata* alertMetadata) {
     bool metadataWritten = false;

     if (mRefractoryPeriodEndsSec.empty()) {
         return false;
     }

     for (const auto& it: mRefractoryPeriodEndsSec) {
         // Do not write the timestamp to disk if it has already expired
         if (it.second < systemElapsedTimeNs / NS_PER_SEC) {
             continue;
         }

         metadataWritten = true;
         if (alertMetadata->alert_dim_keyed_data_size() == 0) {
             alertMetadata->set_alert_id(mAlert.id());
         }

         metadata::AlertDimensionKeyedData* keyedData = alertMetadata->add_alert_dim_keyed_data();
         // We convert and write the refractory_end_sec to wall clock time because we do not know
         // when statsd will start again.
         int32_t refractoryEndWallClockSec = (int32_t) ((currentWallClockTimeNs / NS_PER_SEC) +
                 (it.second - systemElapsedTimeNs / NS_PER_SEC));

         keyedData->set_last_refractory_ends_sec(refractoryEndWallClockSec);
         writeMetricDimensionKeyToMetadataDimensionKey(
                 it.first, keyedData->mutable_dimension_key());
     }

     return metadataWritten;
 }

 void AnomalyTracker::loadAlertMetadata(
         const metadata::AlertMetadata& alertMetadata,
         int64_t currentWallClockTimeNs,
         int64_t systemElapsedTimeNs) {
     for (const metadata::AlertDimensionKeyedData& keyedData :
             alertMetadata.alert_dim_keyed_data()) {
         if ((uint64_t) keyedData.last_refractory_ends_sec() < currentWallClockTimeNs / NS_PER_SEC) {
             // Do not update the timestamp if it has already expired.
             continue;
         }
         MetricDimensionKey metricKey = loadMetricDimensionKeyFromProto(
                 keyedData.dimension_key());
         int32_t refractoryPeriodEndsSec = (int32_t) keyedData.last_refractory_ends_sec() -
                 currentWallClockTimeNs / NS_PER_SEC + systemElapsedTimeNs / NS_PER_SEC;
         mRefractoryPeriodEndsSec[metricKey] = refractoryPeriodEndsSec;
     }
 }

 }  // namespace statsd
 }  // namespace os
 }  // namespace android
	/*
	* Copyright (C) 2017 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#define STATSD_DEBUG false // STOPSHIP if true
	#include "Log.h"

	#include "AnomalyTracker.h"
	#include "external/Perfetto.h"
	#include "guardrail/StatsdStats.h"
	#include "metadata_util.h"
	#include "stats_log_util.h"
	#include "subscriber_util.h"
	#include "subscriber/IncidentdReporter.h"
	#include "subscriber/SubscriberReporter.h"

	#include <inttypes.h>
	#include <statslog_statsd.h>
	#include <time.h>

	namespace android {
	namespace os {
	namespace statsd {

	AnomalyTracker::AnomalyTracker(const Alert& alert, const ConfigKey& configKey)
	: mAlert(alert), mConfigKey(configKey), mNumOfPastBuckets(mAlert.num_buckets() - 1) {
	VLOG("AnomalyTracker() called");
	resetStorage(); // initialization
	}

	AnomalyTracker::~AnomalyTracker() {
	VLOG("~AnomalyTracker() called");
	}

	void AnomalyTracker::onConfigUpdated() {
	mSubscriptions.clear();
	}

	void AnomalyTracker::resetStorage() {
	VLOG("resetStorage() called.");
	mPastBuckets.clear();
	// Excludes the current bucket.
	mPastBuckets.resize(mNumOfPastBuckets);
	mSumOverPastBuckets.clear();
	}

	size_t AnomalyTracker::index(int64_t bucketNum) const {
	if (bucketNum < 0) {
	ALOGE("index() was passed a negative bucket number (%lld)!", (long long)bucketNum);
	}
	return bucketNum % mNumOfPastBuckets;
	}

	void AnomalyTracker::advanceMostRecentBucketTo(const int64_t& bucketNum) {
	VLOG("advanceMostRecentBucketTo() called.");
	if (mNumOfPastBuckets <= 0) {
	return;
	}
	if (bucketNum <= mMostRecentBucketNum) {
	ALOGW("Cannot advance buckets backwards (bucketNum=%lld but mMostRecentBucketNum=%lld)",
	(long long)bucketNum, (long long)mMostRecentBucketNum);
	return;
	}
	// If in the future (i.e. buckets are ancient), just empty out all past info.
	if (bucketNum >= mMostRecentBucketNum + mNumOfPastBuckets) {
	resetStorage();
	mMostRecentBucketNum = bucketNum;
	return;
	}

	// Clear out space by emptying out old mPastBuckets[i] values and update mSumOverPastBuckets.
	for (int64_t i = mMostRecentBucketNum + 1; i <= bucketNum; i++) {
	const int idx = index(i);
	subtractBucketFromSum(mPastBuckets[idx]);
	mPastBuckets[idx] = nullptr; // release (but not clear) the old bucket.
	}
	mMostRecentBucketNum = bucketNum;
	}

	void AnomalyTracker::addPastBucket(const MetricDimensionKey& key,
	const int64_t& bucketValue,
	const int64_t& bucketNum) {
	VLOG("addPastBucket(bucketValue) called.");
	if (mNumOfPastBuckets == 0 \|\|
	bucketNum < 0 \|\| bucketNum <= mMostRecentBucketNum - mNumOfPastBuckets) {
	return;
	}

	const int bucketIndex = index(bucketNum);
	if (bucketNum <= mMostRecentBucketNum && (mPastBuckets[bucketIndex] != nullptr)) {
	// We need to insert into an already existing past bucket.
	std::shared_ptr<DimToValMap>& bucket = mPastBuckets[bucketIndex];
	auto itr = bucket->find(key);
	if (itr != bucket->end()) {
	// Old entry already exists; update it.
	subtractValueFromSum(key, itr->second);
	itr->second = bucketValue;
	} else {
	bucket->insert({key, bucketValue});
	}
	mSumOverPastBuckets[key] += bucketValue;
	} else {
	// Bucket does not exist yet (in future or was never made), so we must make it.
	std::shared_ptr<DimToValMap> bucket = std::make_shared<DimToValMap>();
	bucket->insert({key, bucketValue});
	addPastBucket(bucket, bucketNum);
	}
	}

	void AnomalyTracker::addPastBucket(std::shared_ptr<DimToValMap> bucket,
	const int64_t& bucketNum) {
	VLOG("addPastBucket(bucket) called.");
	if (mNumOfPastBuckets == 0 \|\|
	bucketNum < 0 \|\| bucketNum <= mMostRecentBucketNum - mNumOfPastBuckets) {
	return;
	}

	if (bucketNum <= mMostRecentBucketNum) {
	// We are updating an old bucket, not adding a new one.
	subtractBucketFromSum(mPastBuckets[index(bucketNum)]);
	} else {
	// Clear space for the new bucket to be at bucketNum.
	advanceMostRecentBucketTo(bucketNum);
	}
	mPastBuckets[index(bucketNum)] = bucket;
	addBucketToSum(bucket);
	}

	void AnomalyTracker::subtractBucketFromSum(const shared_ptr<DimToValMap>& bucket) {
	if (bucket == nullptr) {
	return;
	}
	for (const auto& keyValuePair : *bucket) {
	subtractValueFromSum(keyValuePair.first, keyValuePair.second);
	}
	}


	void AnomalyTracker::subtractValueFromSum(const MetricDimensionKey& key,
	const int64_t& bucketValue) {
	auto itr = mSumOverPastBuckets.find(key);
	if (itr == mSumOverPastBuckets.end()) {
	return;
	}
	itr->second -= bucketValue;
	if (itr->second == 0) {
	mSumOverPastBuckets.erase(itr);
	}
	}

	void AnomalyTracker::addBucketToSum(const shared_ptr<DimToValMap>& bucket) {
	if (bucket == nullptr) {
	return;
	}
	// For each dimension present in the bucket, add its value to its corresponding sum.
	for (const auto& keyValuePair : *bucket) {
	mSumOverPastBuckets[keyValuePair.first] += keyValuePair.second;
	}
	}

	int64_t AnomalyTracker::getPastBucketValue(const MetricDimensionKey& key,
	const int64_t& bucketNum) const {
	if (bucketNum < 0 \|\| mMostRecentBucketNum < 0
	\|\| bucketNum <= mMostRecentBucketNum - mNumOfPastBuckets
	\|\| bucketNum > mMostRecentBucketNum) {
	return 0;
	}

	const auto& bucket = mPastBuckets[index(bucketNum)];
	if (bucket == nullptr) {
	return 0;
	}
	const auto& itr = bucket->find(key);
	return itr == bucket->end() ? 0 : itr->second;
	}

	int64_t AnomalyTracker::getSumOverPastBuckets(const MetricDimensionKey& key) const {
	const auto& itr = mSumOverPastBuckets.find(key);
	if (itr != mSumOverPastBuckets.end()) {
	return itr->second;
	}
	return 0;
	}

	bool AnomalyTracker::detectAnomaly(const int64_t& currentBucketNum,
	const MetricDimensionKey& key,
	const int64_t& currentBucketValue) {

	// currentBucketNum should be the next bucket after pastBuckets. If not, advance so that it is.
	if (currentBucketNum > mMostRecentBucketNum + 1) {
	advanceMostRecentBucketTo(currentBucketNum - 1);
	}
	return mAlert.has_trigger_if_sum_gt() &&
	getSumOverPastBuckets(key) + currentBucketValue > mAlert.trigger_if_sum_gt();
	}

	void AnomalyTracker::declareAnomaly(const int64_t& timestampNs, int64_t metricId,
	const MetricDimensionKey& key, int64_t metricValue) {
	// TODO(b/110563466): Why receive timestamp? RefractoryPeriod should always be based on
	// real time right now.
	if (isInRefractoryPeriod(timestampNs, key)) {
	VLOG("Skipping anomaly declaration since within refractory period");
	return;
	}
	if (mAlert.has_refractory_period_secs()) {
	mRefractoryPeriodEndsSec[key] = ((timestampNs + NS_PER_SEC - 1) / NS_PER_SEC) // round up
	+ mAlert.refractory_period_secs();
	// TODO(b/110563466): If we had access to the bucket_size_millis, consider
	// calling resetStorage()
	// if (mAlert.refractory_period_secs() > mNumOfPastBuckets * bucketSizeNs) {resetStorage();}
	}

	if (!mSubscriptions.empty()) {
	ALOGI("An anomaly (%" PRId64 ") %s has occurred! Informing subscribers.",
	mAlert.id(), key.toString().c_str());
	informSubscribers(key, metricId, metricValue);
	} else {
	ALOGI("An anomaly has occurred! (But no subscriber for that alert.)");
	}

	StatsdStats::getInstance().noteAnomalyDeclared(mConfigKey, mAlert.id());

	// TODO(b/110564268): This should also take in the const MetricDimensionKey& key?
	util::stats_write(util::ANOMALY_DETECTED, mConfigKey.GetUid(),
	mConfigKey.GetId(), mAlert.id());
	}

	void AnomalyTracker::detectAndDeclareAnomaly(const int64_t& timestampNs,
	const int64_t& currBucketNum, int64_t metricId,
	const MetricDimensionKey& key,
	const int64_t& currentBucketValue) {
	if (detectAnomaly(currBucketNum, key, currentBucketValue)) {
	declareAnomaly(timestampNs, metricId, key, currentBucketValue);
	}
	}

	bool AnomalyTracker::isInRefractoryPeriod(const int64_t& timestampNs,
	const MetricDimensionKey& key) const {
	const auto& it = mRefractoryPeriodEndsSec.find(key);
	if (it != mRefractoryPeriodEndsSec.end()) {
	return timestampNs < (it->second * (int64_t)NS_PER_SEC);
	}
	return false;
	}

	std::pair<optional<InvalidConfigReason>, uint64_t> AnomalyTracker::getProtoHash() const {
	string serializedAlert;
	if (!mAlert.SerializeToString(&serializedAlert)) {
	ALOGW("Unable to serialize alert %lld", (long long)mAlert.id());
	return {createInvalidConfigReasonWithAlert(INVALID_CONFIG_REASON_ALERT_SERIALIZATION_FAILED,
	mAlert.metric_id(), mAlert.id()),
	0};
	}
	return {nullopt, Hash64(serializedAlert)};
	}

	void AnomalyTracker::informSubscribers(const MetricDimensionKey& key, int64_t metric_id,
	int64_t metricValue) {
	triggerSubscribers(mAlert.id(), metric_id, key, metricValue, mConfigKey, mSubscriptions);
	}

	bool AnomalyTracker::writeAlertMetadataToProto(int64_t currentWallClockTimeNs,
	int64_t systemElapsedTimeNs,
	metadata::AlertMetadata* alertMetadata) {
	bool metadataWritten = false;

	if (mRefractoryPeriodEndsSec.empty()) {
	return false;
	}

	for (const auto& it: mRefractoryPeriodEndsSec) {
	// Do not write the timestamp to disk if it has already expired
	if (it.second < systemElapsedTimeNs / NS_PER_SEC) {
	continue;
	}

	metadataWritten = true;
	if (alertMetadata->alert_dim_keyed_data_size() == 0) {
	alertMetadata->set_alert_id(mAlert.id());
	}

	metadata::AlertDimensionKeyedData* keyedData = alertMetadata->add_alert_dim_keyed_data();
	// We convert and write the refractory_end_sec to wall clock time because we do not know
	// when statsd will start again.
	int32_t refractoryEndWallClockSec = (int32_t) ((currentWallClockTimeNs / NS_PER_SEC) +
	(it.second - systemElapsedTimeNs / NS_PER_SEC));

	keyedData->set_last_refractory_ends_sec(refractoryEndWallClockSec);
	writeMetricDimensionKeyToMetadataDimensionKey(
	it.first, keyedData->mutable_dimension_key());
	}

	return metadataWritten;
	}

	void AnomalyTracker::loadAlertMetadata(
	const metadata::AlertMetadata& alertMetadata,
	int64_t currentWallClockTimeNs,
	int64_t systemElapsedTimeNs) {
	for (const metadata::AlertDimensionKeyedData& keyedData :
	alertMetadata.alert_dim_keyed_data()) {
	if ((uint64_t) keyedData.last_refractory_ends_sec() < currentWallClockTimeNs / NS_PER_SEC) {
	// Do not update the timestamp if it has already expired.
	continue;
	}
	MetricDimensionKey metricKey = loadMetricDimensionKeyFromProto(
	keyedData.dimension_key());
	int32_t refractoryPeriodEndsSec = (int32_t) keyedData.last_refractory_ends_sec() -
	currentWallClockTimeNs / NS_PER_SEC + systemElapsedTimeNs / NS_PER_SEC;
	mRefractoryPeriodEndsSec[metricKey] = refractoryPeriodEndsSec;
	}
	}

	} // namespace statsd
	} // namespace os
	} // namespace android