ClickHouse/dbms/include/DB/Client/ConnectionPoolWithFailover.h
Vladimir Smirnov d36f52502e Make it compilable on OS X
It's still hackish and dirty, but server and client compies.

Server starts, but throwes meaningless exception on any query.

Client seems to be working fine.

Linux compilation might (but shouldn't) be broken (not tested).
2016-11-01 17:59:21 +01:00

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#pragma once
#include <random>
#include <Poco/Net/NetException.h>
#include <Poco/Net/DNS.h>
#include <DB/Common/PoolWithFailoverBase.h>
#include <DB/Common/getFQDNOrHostName.h>
#include <DB/Client/ConnectionPool.h>
namespace DB
{
namespace ErrorCodes
{
extern const int NETWORK_ERROR;
extern const int SOCKET_TIMEOUT;
extern const int LOGICAL_ERROR;
}
/** Пул соединений с отказоустойчивостью.
* Инициализируется несколькими другими IConnectionPool-ами.
* При получении соединения, пытается создать или выбрать живое соединение из какого-нибудь пула,
* перебирая их в некотором порядке, используя не более указанного количества попыток.
* Предпочитаются пулы с меньшим количеством ошибок;
* пулы с одинаковым количеством ошибок пробуются в случайном порядке.
*
* Замечание: если один из вложенных пулов заблокируется из-за переполнения, то этот пул тоже заблокируется.
*/
class ConnectionPoolWithFailover : public PoolWithFailoverBase<IConnectionPool>, public IConnectionPool
{
public:
using Entry = IConnectionPool::Entry;
using Base = PoolWithFailoverBase<IConnectionPool>;
ConnectionPoolWithFailover(ConnectionPools & nested_pools_,
LoadBalancing load_balancing,
size_t max_tries_ = DBMS_CONNECTION_POOL_WITH_FAILOVER_DEFAULT_MAX_TRIES,
time_t decrease_error_period_ = DBMS_CONNECTION_POOL_WITH_FAILOVER_DEFAULT_DECREASE_ERROR_PERIOD)
: Base(nested_pools_, max_tries_, decrease_error_period_,
&Logger::get("ConnectionPoolWithFailover")), default_load_balancing(load_balancing)
{
const std::string & local_hostname = getFQDNOrHostName();
hostname_differences.resize(nested_pools.size());
for (size_t i = 0; i < nested_pools.size(); ++i)
{
ConnectionPool & connection_pool = dynamic_cast<ConnectionPool &>(*nested_pools[i].pool);
const std::string & host = connection_pool.getHost();
size_t hostname_difference = 0;
for (size_t i = 0; i < std::min(local_hostname.length(), host.length()); ++i)
if (local_hostname[i] != host[i])
++hostname_difference;
hostname_differences[i] = hostname_difference;
}
}
protected:
bool tryGet(ConnectionPoolPtr pool, const Settings * settings, Entry & out_entry, std::stringstream & fail_message) override
{
try
{
out_entry = pool->get(settings);
out_entry->forceConnected();
return true;
}
catch (const Exception & e)
{
if (e.code() != ErrorCodes::NETWORK_ERROR && e.code() != ErrorCodes::SOCKET_TIMEOUT)
throw;
fail_message << "Code: " << e.code() << ", e.displayText() = " << e.displayText() << ", e.what() = " << e.what();
return false;
}
}
private:
/** Выделяет соединение для работы. */
Entry doGet(const Settings * settings) override
{
applyLoadBalancing(settings);
return Base::get(settings);
}
/** Выделяет до указанного количества соединений для работы.
* Соединения предоставляют доступ к разным репликам одного шарда.
*/
std::vector<Entry> doGetMany(const Settings * settings, PoolMode pool_mode) override
{
applyLoadBalancing(settings);
return Base::getMany(settings, pool_mode);
}
void applyLoadBalancing(const Settings * settings)
{
LoadBalancing load_balancing = default_load_balancing;
if (settings)
load_balancing = settings->load_balancing;
for (size_t i = 0; i < nested_pools.size(); ++i)
{
if (load_balancing == LoadBalancing::NEAREST_HOSTNAME)
nested_pools[i].state.priority = hostname_differences[i];
else if (load_balancing == LoadBalancing::RANDOM)
nested_pools[i].state.priority = 0;
else if (load_balancing == LoadBalancing::IN_ORDER)
nested_pools[i].state.priority = i;
else
throw Exception("Unknown load_balancing_mode: " + toString(static_cast<int>(load_balancing)), ErrorCodes::LOGICAL_ERROR);
}
}
private:
std::vector<size_t> hostname_differences; /// Расстояния от имени этого хоста до имен хостов пулов.
LoadBalancing default_load_balancing;
};
}