mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-12 01:12:12 +00:00
60 lines
1.8 KiB
C++
60 lines
1.8 KiB
C++
#pragma once
|
|
#include <Common/ZooKeeper/ZooKeeper.h>
|
|
#include <Common/ZooKeeper/KeeperException.h>
|
|
#include <memory>
|
|
#include <string>
|
|
|
|
namespace Poco { class Logger; }
|
|
|
|
namespace zkutil
|
|
{
|
|
|
|
/** Caveats: usage of locks in ZooKeeper is incorrect in 99% of cases,
|
|
* and highlights your poor understanding of distributed systems.
|
|
*
|
|
* It's only correct if all the operations that are performed under lock
|
|
* are atomically checking that the lock still holds
|
|
* or if we ensure that these operations will be undone if lock is lost
|
|
* (due to ZooKeeper session loss) that's very difficult to achieve.
|
|
*
|
|
* It's Ok if every operation that we perform under lock is actually operation in ZooKeeper.
|
|
*
|
|
* In 1% of cases when you can correctly use Lock, the logic is complex enough, so you don't need this class.
|
|
*
|
|
* TLDR: Don't use this code if you are not sure. We only have a few cases of it's usage.
|
|
*/
|
|
class ZooKeeperLock
|
|
{
|
|
public:
|
|
/// lock_prefix - path where the ephemeral lock node will be created
|
|
/// lock_name - the name of the ephemeral lock node
|
|
ZooKeeperLock(
|
|
const ZooKeeperPtr & zookeeper_,
|
|
const std::string & lock_prefix_,
|
|
const std::string & lock_name_,
|
|
const std::string & lock_message_ = "",
|
|
bool throw_if_lost_ = true);
|
|
|
|
~ZooKeeperLock();
|
|
|
|
void unlock();
|
|
bool tryLock();
|
|
bool isLocked() const;
|
|
const std::string & getLockPath() const;
|
|
|
|
private:
|
|
zkutil::ZooKeeperPtr zookeeper;
|
|
|
|
std::string lock_path;
|
|
std::string lock_message;
|
|
bool throw_if_lost{true};
|
|
LoggerPtr log;
|
|
bool locked = false;
|
|
|
|
};
|
|
|
|
std::unique_ptr<ZooKeeperLock> createSimpleZooKeeperLock(
|
|
const ZooKeeperPtr & zookeeper, const String & lock_prefix, const String & lock_name, const String & lock_message, bool throw_if_lost = true);
|
|
|
|
}
|