mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-09-23 18:20:50 +00:00
143 lines
3.4 KiB
C++
143 lines
3.4 KiB
C++
#pragma once
|
||
|
||
#include <zkutil/ZooKeeper.h>
|
||
#include <functional>
|
||
#include <Yandex/logger_useful.h>
|
||
|
||
|
||
namespace zkutil
|
||
{
|
||
|
||
/** Реализует метод выбора лидера, описанный здесь: http://zookeeper.apache.org/doc/r3.4.5/recipes.html#sc_leaderElection
|
||
*/
|
||
class LeaderElection
|
||
{
|
||
public:
|
||
typedef std::function<void()> LeadershipHandler;
|
||
|
||
/** handler вызывается, когда этот экземпляр становится лидером.
|
||
*/
|
||
LeaderElection(const std::string & path_, ZooKeeper & zookeeper_, LeadershipHandler handler_, const std::string & identifier_ = "")
|
||
: path(path_), zookeeper(zookeeper_), handler(handler_), identifier(identifier_),
|
||
shutdown(false), state(WAITING_LEADERSHIP), log(&Logger::get("LeaderElection"))
|
||
{
|
||
node = EphemeralNodeHolder::createSequential(path + "/leader_election-", zookeeper, identifier);
|
||
|
||
std::string node_path = node->getPath();
|
||
node_name = node_path.substr(node_path.find_last_of('/') + 1);
|
||
|
||
thread = std::thread(&LeaderElection::threadFunction, this);
|
||
}
|
||
|
||
enum State
|
||
{
|
||
WAITING_LEADERSHIP,
|
||
LEADER,
|
||
LEADERSHIP_LOST
|
||
};
|
||
|
||
/// если возвращает LEADER, то еще sessionTimeoutMs мы будем лидером, даже если порвется соединение с zookeeper
|
||
State getState()
|
||
{
|
||
if (state == LEADER)
|
||
{
|
||
try
|
||
{
|
||
/// возможно, если сессия разорвалась и заново был вызван init
|
||
if (!zookeeper.exists(node->getPath()))
|
||
{
|
||
LOG_WARNING(log, "Leadership lost. Node " << node->getPath() << " doesn't exist.");
|
||
state = LEADERSHIP_LOST;
|
||
}
|
||
}
|
||
catch (const KeeperException & e)
|
||
{
|
||
LOG_WARNING(log, "Leadership lost. e.message() = " << e.message());
|
||
state = LEADERSHIP_LOST;
|
||
}
|
||
}
|
||
|
||
return state;
|
||
|
||
}
|
||
|
||
~LeaderElection()
|
||
{
|
||
shutdown = true;
|
||
event->set();
|
||
thread.join();
|
||
}
|
||
|
||
private:
|
||
std::string path;
|
||
ZooKeeper & zookeeper;
|
||
LeadershipHandler handler;
|
||
std::string identifier;
|
||
|
||
EphemeralNodeHolderPtr node;
|
||
std::string node_name;
|
||
|
||
std::thread thread;
|
||
volatile bool shutdown;
|
||
zkutil::EventPtr event = new Poco::Event();
|
||
|
||
State state;
|
||
|
||
Logger * log;
|
||
|
||
void threadFunction()
|
||
{
|
||
while (!shutdown)
|
||
{
|
||
bool success = false;
|
||
|
||
try
|
||
{
|
||
Strings children = zookeeper.getChildren(path);
|
||
std::sort(children.begin(), children.end());
|
||
auto it = std::lower_bound(children.begin(), children.end(), node_name);
|
||
if (it == children.end() || *it != node_name)
|
||
throw Poco::Exception("Assertion failed in LeaderElection");
|
||
|
||
if (it == children.begin())
|
||
{
|
||
state = LEADER;
|
||
handler();
|
||
return;
|
||
}
|
||
|
||
if (zookeeper.exists(path + "/" + *(it - 1), nullptr, event))
|
||
event->wait();
|
||
|
||
success = true;
|
||
}
|
||
catch (const DB::Exception & e)
|
||
{
|
||
LOG_ERROR(log, "Exception in LeaderElection: Code: " << e.code() << ". " << e.displayText() << std::endl
|
||
<< std::endl
|
||
<< "Stack trace:" << std::endl
|
||
<< e.getStackTrace().toString());
|
||
}
|
||
catch (const Poco::Exception & e)
|
||
{
|
||
LOG_ERROR(log, "Poco::Exception in LeaderElection: " << e.code() << ". " << e.displayText());
|
||
}
|
||
catch (const std::exception & e)
|
||
{
|
||
LOG_ERROR(log, "std::exception in LeaderElection: " << e.what());
|
||
}
|
||
catch (...)
|
||
{
|
||
LOG_ERROR(log, "Unknown exception in LeaderElection");
|
||
}
|
||
|
||
if (!success)
|
||
event->tryWait(10 * 1000);
|
||
}
|
||
}
|
||
};
|
||
|
||
typedef Poco::SharedPtr<LeaderElection> LeaderElectionPtr;
|
||
|
||
}
|