/*
 * Ratekeeper.h
 *
 * This source file is part of the FoundationDB open source project
 *
 * Copyright 2013-2022 Apple Inc. and the FoundationDB project authors
 *
 * 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.
 */

#pragma once

#include "fdbclient/DatabaseConfiguration.h"
#include "fdbclient/DatabaseContext.h"
#include "fdbclient/StorageServerInterface.h"
#include "fdbclient/TagThrottle.actor.h"
#include "fdbrpc/Smoother.h"
#include "fdbserver/Knobs.h"
#include "fdbserver/RatekeeperInterface.h"
#include "fdbserver/ServerDBInfo.h"
#include "fdbserver/TLogInterface.h"

enum limitReason_t {
	unlimited, // TODO: rename to workload?
	storage_server_write_queue_size, // 1
	storage_server_write_bandwidth_mvcc,
	storage_server_readable_behind,
	log_server_mvcc_write_bandwidth,
	log_server_write_queue, // 5
	storage_server_min_free_space, // a storage server's normal limits are being reduced by low free space
	storage_server_min_free_space_ratio, // a storage server's normal limits are being reduced by a low free space ratio
	log_server_min_free_space,
	log_server_min_free_space_ratio,
	storage_server_durability_lag, // 10
	storage_server_list_fetch_failed,
	limitReason_t_end
};

class StorageQueueInfo {
	uint64_t totalWriteCosts{ 0 };
	int totalWriteOps{ 0 };
	Reference<EventCacheHolder> busiestWriteTagEventHolder;

	// refresh periodically
	TransactionTagMap<TransactionCommitCostEstimation> tagCostEst;

public:
	bool valid;
	UID id;
	LocalityData locality;
	StorageQueuingMetricsReply lastReply;
	bool acceptingRequests;
	Smoother smoothDurableBytes, smoothInputBytes, verySmoothDurableBytes;
	Smoother smoothDurableVersion, smoothLatestVersion;
	Smoother smoothFreeSpace;
	Smoother smoothTotalSpace;
	limitReason_t limitReason;
	std::vector<StorageQueuingMetricsReply::TagInfo> busiestReadTags, busiestWriteTags;

	StorageQueueInfo(UID id, LocalityData locality);
	void refreshCommitCost(double elapsed);
	int64_t getStorageQueueBytes() const { return lastReply.bytesInput - smoothDurableBytes.smoothTotal(); }
	int64_t getDurabilityLag() const { return smoothLatestVersion.smoothTotal() - smoothDurableVersion.smoothTotal(); }
	void update(StorageQueuingMetricsReply const&, Smoother& smoothTotalDurableBytes);
	void addCommitCost(TransactionTagRef tagName, TransactionCommitCostEstimation const& cost);
};

struct TLogQueueInfo {
	TLogQueuingMetricsReply lastReply;
	bool valid;
	UID id;
	Smoother smoothDurableBytes, smoothInputBytes, verySmoothDurableBytes;
	Smoother smoothFreeSpace;
	Smoother smoothTotalSpace;

	TLogQueueInfo(UID id);
	Version getLastCommittedVersion() const { return lastReply.v; }
	void update(TLogQueuingMetricsReply const& reply, Smoother& smoothTotalDurableBytes);
};

struct RatekeeperLimits {
	double tpsLimit;
	Int64MetricHandle tpsLimitMetric;
	Int64MetricHandle reasonMetric;

	int64_t storageTargetBytes;
	int64_t storageSpringBytes;
	int64_t logTargetBytes;
	int64_t logSpringBytes;
	double maxVersionDifference;

	int64_t durabilityLagTargetVersions;
	int64_t lastDurabilityLag;
	double durabilityLagLimit;

	TransactionPriority priority;
	std::string context;

	Reference<EventCacheHolder> rkUpdateEventCacheHolder;

	RatekeeperLimits(TransactionPriority priority,
	                 std::string context,
	                 int64_t storageTargetBytes,
	                 int64_t storageSpringBytes,
	                 int64_t logTargetBytes,
	                 int64_t logSpringBytes,
	                 double maxVersionDifference,
	                 int64_t durabilityLagTargetVersions);
};

class Ratekeeper {
	friend class RatekeeperImpl;

	// Differentiate from GrvProxyInfo in DatabaseContext.h
	struct GrvProxyInfo {
		int64_t totalTransactions{ 0 };
		int64_t batchTransactions{ 0 };
		uint64_t lastThrottledTagChangeId{ 0 };

		double lastUpdateTime{ 0.0 };
		double lastTagPushTime{ 0.0 };
	};

	UID id;
	Database db;

	Map<UID, StorageQueueInfo> storageQueueInfo;
	Map<UID, TLogQueueInfo> tlogQueueInfo;

	std::map<UID, Ratekeeper::GrvProxyInfo> grvProxyInfo;
	Smoother smoothReleasedTransactions, smoothBatchReleasedTransactions, smoothTotalDurableBytes;
	HealthMetrics healthMetrics;
	DatabaseConfiguration configuration;
	PromiseStream<Future<Void>> addActor;

	Int64MetricHandle actualTpsMetric;

	double lastWarning;
	double lastSSListFetchedTimestamp;

	std::unique_ptr<class TagThrottler> tagThrottler;

	RatekeeperLimits normalLimits;
	RatekeeperLimits batchLimits;

	Deque<double> actualTpsHistory;
	Optional<Key> remoteDC;

	Ratekeeper(UID id, Database db);

	Future<Void> configurationMonitor();
	void updateCommitCostEstimation(UIDTransactionTagMap<TransactionCommitCostEstimation> const& costEstimation);
	void updateRate(RatekeeperLimits* limits);
	Future<Void> refreshStorageServerCommitCosts();
	Future<Void> monitorServerListChange(PromiseStream<std::pair<UID, Optional<StorageServerInterface>>> serverChanges);
	Future<Void> trackEachStorageServer(FutureStream<std::pair<UID, Optional<StorageServerInterface>>> serverChanges);

	// SOMEDAY: template trackStorageServerQueueInfo and trackTLogQueueInfo into one function
	Future<Void> trackStorageServerQueueInfo(StorageServerInterface);
	Future<Void> trackTLogQueueInfo(TLogInterface);

	void tryAutoThrottleTag(TransactionTag, double rate, double busyness, TagThrottledReason);
	void tryAutoThrottleTag(StorageQueueInfo&, int64_t storageQueue, int64_t storageDurabilityLag);
	Future<Void> monitorThrottlingChanges();

public:
	static Future<Void> run(RatekeeperInterface rkInterf, Reference<AsyncVar<ServerDBInfo> const> dbInfo);
};