ClickHouse/dbms/include/DB/Client/Connection.h

#pragma once

#include <common/logger_useful.h>

#include <Poco/Net/StreamSocket.h>

#include <DB/Common/Throttler.h>

#include <DB/Core/Block.h>
#include <DB/Core/Defines.h>
#include <DB/Core/Progress.h>
#include <DB/Core/Protocol.h>
#include <DB/Core/QueryProcessingStage.h>

#include <DB/DataStreams/IBlockInputStream.h>
#include <DB/DataStreams/IBlockOutputStream.h>
#include <DB/DataStreams/BlockStreamProfileInfo.h>

#include <DB/Interpreters/Settings.h>

#include <atomic>


namespace DB
{

class ClientInfo;

/// Поток блоков читающих из таблицы и ее имя
using ExternalTableData = std::pair<BlockInputStreamPtr, std::string>;
/// Вектор пар, описывающих таблицы
using ExternalTablesData = std::vector<ExternalTableData>;

class Connection;

using ConnectionPtr = std::shared_ptr<Connection>;
using Connections = std::vector<ConnectionPtr>;


/** Connection with database server, to use by client.
  * How to use - see Core/Protocol.h
  * (Implementation of server end - see Server/TCPHandler.h)
  *
  * As 'default_database' empty string could be passed
  *  - in that case, server will use it's own default database.
  */
class Connection : private boost::noncopyable
{
	friend class ParallelReplicas;
	friend class MultiplexedConnections;

public:
	Connection(const String & host_, UInt16 port_, const String & default_database_,
		const String & user_, const String & password_,
		const String & client_name_ = "client",
		Protocol::Compression::Enum compression_ = Protocol::Compression::Enable,
		Poco::Timespan connect_timeout_ = Poco::Timespan(DBMS_DEFAULT_CONNECT_TIMEOUT_SEC, 0),
		Poco::Timespan receive_timeout_ = Poco::Timespan(DBMS_DEFAULT_RECEIVE_TIMEOUT_SEC, 0),
		Poco::Timespan send_timeout_ = Poco::Timespan(DBMS_DEFAULT_SEND_TIMEOUT_SEC, 0),
		Poco::Timespan ping_timeout_ = Poco::Timespan(DBMS_DEFAULT_PING_TIMEOUT_SEC, 0))
		:
		host(host_), port(port_), default_database(default_database_),
		user(user_), password(password_), resolved_address(host, port),
		client_name(client_name_),
		compression(compression_),
		connect_timeout(connect_timeout_), receive_timeout(receive_timeout_), send_timeout(send_timeout_),
		ping_timeout(ping_timeout_),
		log_wrapper(*this)
	{
		/// Don't connect immediately, only on first need.

		if (user.empty())
			user = "default";

		setDescription();
	}

	Connection(const String & host_, UInt16 port_, const Poco::Net::SocketAddress & resolved_address_,
		const String & default_database_,
		const String & user_, const String & password_,
		const String & client_name_ = "client",
		Protocol::Compression::Enum compression_ = Protocol::Compression::Enable,
		Poco::Timespan connect_timeout_ = Poco::Timespan(DBMS_DEFAULT_CONNECT_TIMEOUT_SEC, 0),
		Poco::Timespan receive_timeout_ = Poco::Timespan(DBMS_DEFAULT_RECEIVE_TIMEOUT_SEC, 0),
		Poco::Timespan send_timeout_ = Poco::Timespan(DBMS_DEFAULT_SEND_TIMEOUT_SEC, 0),
		Poco::Timespan ping_timeout_ = Poco::Timespan(DBMS_DEFAULT_PING_TIMEOUT_SEC, 0))
		:
		host(host_), port(port_),
		default_database(default_database_),
		user(user_), password(password_),
		resolved_address(resolved_address_),
		client_name(client_name_),
		compression(compression_),
		connect_timeout(connect_timeout_), receive_timeout(receive_timeout_), send_timeout(send_timeout_),
		ping_timeout(ping_timeout_),
		log_wrapper(*this)
	{
		/// Don't connect immediately, only on first need.

		if (user.empty())
			user = "default";

		setDescription();
	}

	virtual ~Connection() {};

	/// Set throttler of network traffic. One throttler could be used for multiple connections to limit total traffic.
	void setThrottler(const ThrottlerPtr & throttler_)
	{
		throttler = throttler_;
	}


	/// Packet that could be received from server.
	struct Packet
	{
		UInt64 type;

		Block block;
		std::unique_ptr<Exception> exception;
		Progress progress;
		BlockStreamProfileInfo profile_info;

		Packet() : type(Protocol::Server::Hello) {}
	};

	/// Change default database. Changes will take effect on next reconnect.
	void setDefaultDatabase(const String & database);

	void getServerVersion(String & name, UInt64 & version_major, UInt64 & version_minor, UInt64 & revision);

	const String & getServerTimezone();

	/// For log and exception messages.
	const String & getDescription() const;
	const String & getHost() const;
	UInt16 getPort() const;
	const String & getDefaultDatabase() const;

	/// If last flag is true, you need to call sendExternalTablesData after.
	void sendQuery(
		const String & query,
		const String & query_id_ = "",
		UInt64 stage = QueryProcessingStage::Complete,
		const Settings * settings = nullptr,
		const ClientInfo * client_info = nullptr,
		bool with_pending_data = false);

	void sendCancel();
	/// Send block of data; if name is specified, server will write it to external (temporary) table of that name.
	void sendData(const Block & block, const String & name = "");
	/// Send all contents of external (temporary) tables.
	void sendExternalTablesData(ExternalTablesData & data);

	/// Send prepared block of data (serialized and, if need, compressed), that will be read from 'input'.
	/// You could pass size of serialized/compressed block.
	void sendPreparedData(ReadBuffer & input, size_t size, const String & name = "");

	/// Check, if has data to read.
	bool poll(size_t timeout_microseconds = 0);

	/// Check, if has data in read buffer.
	bool hasReadBufferPendingData() const;

	/// Receive packet from server.
	Packet receivePacket();

	/// If not connected yet, or if connection is broken - then connect. If cannot connect - throw an exception.
	void forceConnected();

	/** Disconnect.
	  * This may be used, if connection is left in unsynchronised state
	  *  (when someone continues to wait for something) after an exception.
	  */
	void disconnect();

	/** Заполнить информацию, которая необходима при получении блока для некоторых задач
	  * (пока только для запроса DESCRIBE TABLE с Distributed-таблицами).
	  */
	void fillBlockExtraInfo(BlockExtraInfo & info) const;

	size_t outBytesCount() const { return out ? out->count() : 0; }
	size_t inBytesCount() const { return in ? in->count() : 0; }

private:
	String host;
	UInt16 port;
	String default_database;
	String user;
	String password;

	/** Address could be resolved beforehand and passed to constructor. Then 'host' and 'port' fields are used just for logging.
	  * Otherwise address is resolved in constructor. Thus, DNS based load balancing is not supported.
	  */
	Poco::Net::SocketAddress resolved_address;

	/// Для сообщений в логе и в эксепшенах.
	String description;
	void setDescription();

	String client_name;

	bool connected = false;

	String server_name;
	UInt64 server_version_major = 0;
	UInt64 server_version_minor = 0;
	UInt64 server_revision = 0;
	String server_timezone;

	Poco::Net::StreamSocket socket;
	std::shared_ptr<ReadBuffer> in;
	std::shared_ptr<WriteBuffer> out;

	String query_id;
	UInt64 compression;		/// Enable data compression for communication.
	/// What compression algorithm to use while sending data for INSERT queries and external tables.
	CompressionMethod network_compression_method = CompressionMethod::LZ4;

	/** If not nullptr, used to limit network traffic.
	  * Only traffic for transferring blocks is accounted. Other packets don't.
	  */
	ThrottlerPtr throttler;

	Poco::Timespan connect_timeout;
	Poco::Timespan receive_timeout;
	Poco::Timespan send_timeout;
	Poco::Timespan ping_timeout;

	/// From where to read query execution result.
	std::shared_ptr<ReadBuffer> maybe_compressed_in;
	BlockInputStreamPtr block_in;

	/// Where to write data for INSERT.
	std::shared_ptr<WriteBuffer> maybe_compressed_out;
	BlockOutputStreamPtr block_out;

	/// Logger is created lazily, for avoid to run DNS request in constructor.
	class LoggerWrapper
	{
	public:
		LoggerWrapper(Connection & parent_)
			: log(nullptr), parent(parent_)
		{
		}

		Logger * get()
		{
			if (!log)
				log = &Logger::get("Connection (" + parent.getDescription() + ")");

			return log;
		}

	private:
		std::atomic<Logger *> log;
		Connection & parent;
	};

	LoggerWrapper log_wrapper;

	void connect();
	void sendHello();
	void receiveHello();
	bool ping();

	Block receiveData();
	std::unique_ptr<Exception> receiveException();
	Progress receiveProgress();
	BlockStreamProfileInfo receiveProfileInfo();

	void initBlockInput();
};

}