mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-10-25 18:00:51 +00:00
128 lines
2.9 KiB
C++
128 lines
2.9 KiB
C++
|
#pragma once
|
|||
|
|
|||
|
#include <zkutil/ZooKeeper.h>
|
|||
|
#include <functional>
|
|||
|
#include <common/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_),
|
|||
|
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 = false;
|
|||
|
zkutil::EventPtr event = new Poco::Event();
|
|||
|
|
|||
|
State state = WAITING_LEADERSHIP;
|
|||
|
|
|||
|
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 (...)
|
|||
|
{
|
|||
|
DB::tryLogCurrentException("LeaderElection");
|
|||
|
}
|
|||
|
|
|||
|
if (!success)
|
|||
|
event->tryWait(10 * 1000);
|
|||
|
}
|
|||
|
}
|
|||
|
};
|
|||
|
|
|||
|
typedef Poco::SharedPtr<LeaderElection> LeaderElectionPtr;
|
|||
|
|
|||
|
}
|