mysql实现分布式锁

利用数据库的悲观锁实现分布式锁,实际应用中要考虑mysql的高可用。

DistributedLock.h

#ifndef DistributedLock_H_
#define DistributedLock_H_//
// DistributedLock.h: 
//
#include "base/MySQLDriver.h"
class CDistributedLock
{
public://// Construction/Destruction//CDistributedLock(server::mysqldb::MySQLConnection* c, const std::string& path, uint64_t key, uint16_t partitions = 16);~CDistributedLock();operator bool(){return m_bLocked;}bool getLocked(){return m_bLocked;}bool getDbDeaded(){return m_bDbDead;}private:server::mysqldb::MySQLConnection* con_;bool		m_bLocked; //获取分布式锁是否成功bool		m_bDbDead;  //数据库是否是否宕机
};
#endif

DistributedLock.cpp

//
// DistributedLock.cpp: 
//#include "DistributedLock.h"
#include "logger.h"
#include "base/common.h"
#include <string>
#include <sys/timeb.h>
#include <time.h>//
// Construction/Destruction
//char*   log_Time(void)
{struct  tm      *ptm;struct  timeb   stTimeb;static  char    szTime[19];ftime(&stTimeb);ptm = localtime(&stTimeb.time);sprintf(szTime, "%02d-%02d %02d:%02d:%02d.%03d",ptm->tm_mon + 1, ptm->tm_mday, ptm->tm_hour, ptm->tm_min, ptm->tm_sec, stTimeb.millitm);szTime[18] = 0;return szTime;
}CDistributedLock::CDistributedLock(server::mysqldb::MySQLConnection* c,const std::string& path,uint64_t key,uint16_t partitions) 
{m_bLocked = false ;m_bDbDead = false;con_ = c ;if ( c ){server::mysqldb::Statement st = c->createStatement() ;char szSQL[256] ;sprintf(szSQL,"insert into %s_%d (lock_key,lock_ts) values (" UINT64FORMAT ",now()) on duplicate key update lock_ts=now()",path.c_str(),uint16_t(key % partitions), key) ;st.prepare(szSQL) ;int errcode = 0;std::string errwhat;for(int i = 0; i < 3; ++i) {try {server::mysqldb::ResultSet result = st.execute();if (result.getAffectedRows() > 0){LogTrace(Info, "Distributed lock get succeed , affectedRows %d tms %s", result.getAffectedRows(), log_Time());m_bLocked = true;}else{LogTrace(Warn, "Distributed lock get failed , affectedRows %d tms %s", result.getAffectedRows(), log_Time());}break;} catch (server::mysqldb::Exception &e) {c->reconnect();errcode = e.code();errwhat = e.what();LogTrace(Error, "statemt error, %d %s try again !", errcode, errwhat.c_str());}}if(!m_bLocked) {LogTrace(Error, "sql execute error, code:%d, reason:%s", errcode, errwhat.c_str());}}else{LogTrace(Error, "get distributed lock failed, lock db is gone !");m_bDbDead = true;}
}CDistributedLock::~CDistributedLock()
{	if ( con_ ) {try {m_bLocked ? con_->commit() : con_->rollback() ;} catch (server::mysqldb::Exception &e) {	LogTrace(Error, "commit execute error, code:%d, reason:%s", e.code(), e.what());	con_->close() ;}}
}