ZKLockGuard

An implementation of distributed lock with zookeeper.

Instruction

class ZKLockGuard;

(constructor)

ZKLockGuard(zhandle_t *zh, const char *zkLockPath, const char *uniqueString);

When a ZKLockGuard object is created, it attempts to create a zookeeper node with type ZOO_EPHEMERAL|ZOO_SEQUENCE under path zkLockPath, for example,

{zkLockPath}/lock_{uniqueString}_{zookeeper_generated_sequence_number}.

if the {zookeeper_generated_sequence_number} is the smallest one, the distributed lock is acquired, otherwise it will wait.

When control leaves the scope in which the ZKLockGuard object was created, the ZKLockGuard is destructed, the zookeeper node is removed, and the distributed lock is released.

Example

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "ZKLockGuard.h"

void defaultWatcher(zhandle_t* zh, int type, int state, const char* path, void* watcherCtx) {
	//do nothing.
}

zhandle_t* zh = NULL;

bool init(const char* zkHost)
{
	int count = 0;
	do {
		count++;
		zh = zookeeper_init(zkHost, &defaultWatcher, 10000, 0, NULL, 0);
	} while (!zh && count < 3);

	if (!zh) {
		printf("zookeeper_init failed!!!\n");
		return false;
	}
	else {
		printf("zookeeper_init successfully.\n");
	}
	return true;
}

int main()
{
	if (!init("192.168.7.171:2181,192.168.7.172:2181,192.168.7.173:2181")) {
		return -1;
	}

	{
		//attemp to lock
		ZKLockGuard lock(zh, "/dlock/test", "myUniqueString");
		//got the lock, 
		//do something
		sleep(10);
	}
	//lock is released.

	return 0;
}

Dependency

• -lzookeeper_mt
• -lpthread
• c++11