ClickHouse/programs/odbc-bridge/ODBCConnectionFactory.h

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#pragma once
#include <common/logger_useful.h>
#include <nanodbc/nanodbc.h>
#include <mutex>
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#include <common/BorrowedObjectPool.h>
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#include <unordered_map>
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namespace DB
{
namespace ErrorCodes
{
extern const int NO_FREE_CONNECTION;
}
}
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namespace nanodbc
{
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using ConnectionPtr = std::unique_ptr<nanodbc::connection>;
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using Pool = BorrowedObjectPool<ConnectionPtr>;
using PoolPtr = std::shared_ptr<Pool>;
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static constexpr inline auto ODBC_CONNECT_TIMEOUT = 100;
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class ConnectionHolder
{
public:
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ConnectionHolder(PoolPtr pool_,
ConnectionPtr connection_,
const String & connection_string_)
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: pool(pool_)
, connection(std::move(connection_))
, connection_string(connection_string_)
{
}
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ConnectionHolder(const ConnectionHolder & other) = delete;
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~ConnectionHolder()
{
pool->returnObject(std::move(connection));
}
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nanodbc::connection & get() const
{
assert(connection != nullptr);
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return *connection;
}
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void updateConnection()
{
connection = std::make_unique<nanodbc::connection>(connection_string, ODBC_CONNECT_TIMEOUT);
}
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private:
PoolPtr pool;
ConnectionPtr connection;
String connection_string;
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};
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using ConnectionHolderPtr = std::shared_ptr<ConnectionHolder>;
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}
namespace DB
{
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static constexpr inline auto ODBC_CONNECT_TIMEOUT = 100;
static constexpr inline auto ODBC_POOL_WAIT_TIMEOUT = 10000;
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template <typename T>
T execute(nanodbc::ConnectionHolderPtr connection_holder, std::function<T(nanodbc::connection &)> query_func)
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{
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try
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{
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return query_func(connection_holder->get());
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}
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catch (const nanodbc::database_error & e)
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{
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/// SQLState, connection related errors start with 08S0.
if (e.state().starts_with("08S0"))
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{
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connection_holder->updateConnection();
return query_func(connection_holder->get());
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}
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throw;
}
}
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class ODBCConnectionFactory final : private boost::noncopyable
{
public:
static ODBCConnectionFactory & instance()
{
static ODBCConnectionFactory ret;
return ret;
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}
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nanodbc::ConnectionHolderPtr get(const std::string & connection_string, size_t pool_size)
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{
std::lock_guard lock(mutex);
if (!factory.count(connection_string))
factory.emplace(std::make_pair(connection_string, std::make_shared<nanodbc::Pool>(pool_size)));
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auto & pool = factory[connection_string];
nanodbc::ConnectionPtr connection;
auto connection_available = pool->tryBorrowObject(connection, []() { return nullptr; }, ODBC_POOL_WAIT_TIMEOUT);
if (!connection_available)
throw Exception("Unable to fetch connection within the timeout", ErrorCodes::NO_FREE_CONNECTION);
try
{
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if (!connection)
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connection = std::make_unique<nanodbc::connection>(connection_string, ODBC_CONNECT_TIMEOUT);
}
catch (...)
{
pool->returnObject(std::move(connection));
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throw;
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}
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return std::make_unique<nanodbc::ConnectionHolder>(factory[connection_string], std::move(connection), connection_string);
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}
private:
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/// [connection_settings_string] -> [connection_pool]
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using PoolFactory = std::unordered_map<std::string, nanodbc::PoolPtr>;
PoolFactory factory;
std::mutex mutex;
};
}