tair 實現分佈式鎖

原創

2020-02-21 06:56

0 概述

在實際工作中，服務都是在分佈式環境下，需要有一個分佈式鎖，來解決分佈式環境下的併發問題。本文主要講述如何用tair 實現分佈式鎖。
依賴pom

<dependency>
    <groupId>com.taobao.tair</groupId>
    <artifactId>tair-client</artifactId>
    <version>2.3.4</version>
</dependency

1 實現思路

TairManager.put 傳入version（version>0）版本進行校驗，cas原則會保證只有一個能成功，tair 在第一次put時候 version=1。

具體實現代碼

import com.taobao.tair.DataEntry;
import com.taobao.tair.Result;
import com.taobao.tair.ResultCode;
import com.taobao.tair.impl.DefaultTairManager;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.util.ArrayList;
import java.util.List;

/**
 * Created by hsc on 17/10/18.
 */
@Component
public class TairWrapper {
    private DefaultTairManager tairManager;

    @Value("${tair.master}")
    private String master;
    @Value("${tair.slave}")
    private String slave;
    @Value("${tair.groupname}")
    private String groupname;
    @Value("${tair.namespace}")
    private int namespace;

    @PostConstruct
    private void init() throws Exception {
        tairManager = new DefaultTairManager();
        List<String> configserverList = new ArrayList<String>();
        configserverList.add(master);
        configserverList.add(slave);
        tairManager.setConfigServerList(configserverList);
        tairManager.setGroupName(groupname);

        tairManager.init();
    }

    public ResultCode put(String key, String value, int expireTime) {
        return tairManager.put(namespace, key, value, expireTime);
    }

    public ResultCode put(String key, String value, int version, int expireTime) {
        return tairManager.put(namespace, key, value, version, expireTime);
    }

    public Result<DataEntry> get(String key) {
        return tairManager.get(namespace, key);
    }

    public ResultCode delete(String key) {
        return tairManager.delete(namespace, key);
    }

package com.mogujie.enzo.service.tair.impl;

import com.mogujie.enzo.tair.TairWrapper;
import com.taobao.tair.DataEntry;
import com.taobao.tair.Result;
import com.taobao.tair.ResultCode;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;

/**
 * Created by hsc on 17/10/18.
 */
@Service("lockService")
public class LockService {
    /**
     * 鎖過期時間 5s
     */
    private static final int LOCK_EXPIRE_TIME = 5;
    @Resource
    private TairWrapper tairWrapper;
    /**
     * tair 在第一次put version=1
     * 當 version 大於0時候,會根據version 比較,如果vesion 相等則更新
     * version=0 時候會更新
     */
    private final static int INIT_VERSION = 2;

    private static final int lockWaitTimeOut = 5000;

    private static final int retryTime = 200;

    private static final Logger logger = LoggerFactory.getLogger(LockService.class);
//獲取鎖
    public boolean getCacheLock(String cacheKey) {
        if (StringUtils.isEmpty(cacheKey)) {
            return true;
        }
        int waitTimeOut = lockWaitTimeOut;
        try {
            while (waitTimeOut > 0) {
                //如果put成功說明加鎖成功
                if (this.setnxWithExpire(cacheKey, cacheKey)) {
                    return true;
                }
                waitTimeOut -= retryTime;
                //如果 tair 掛了這裏會異常，快速失敗
                String value = this.getLockValue(cacheKey);
                if (value == null) {
                    continue;
                }
                sleep(retryTime);
            }
            //程序走到這裏說明鎖等待一定的時間,所以這裏釋放這個鎖
            delCacheLock(cacheKey);
        } catch (Exception ex) {
            logger.error("getCacheLock exception key:{}", cacheKey, ex);
        }

        return true;
    }
    //釋放鎖
    public boolean delCacheLock(String cacheKey) {
        try {
            ResultCode result = tairWrapper.delete(cacheKey);
            return ResultCode.SUCCESS.equals(result);
        } catch (Exception ex) {
            logger.error("delete cacheKey exception key:{}", cacheKey, ex);
        }
        return false;
    }

    private void sleep(long millis) {
        try {
            Thread.sleep(millis);
        } catch (Exception ex) {
            logger.error("sleep exception", ex);
        }
    }

    private String getLockValue(String lockKey) {
        Result<DataEntry> getResult = tairWrapper.get(lockKey);
        if (getResult != null && ResultCode.SUCCESS.equals(getResult.getRc())) {
            Object obj = getResult.getValue().getValue();
            return obj == null ? null : obj.toString();
        }
        return null;
    }

    private boolean setnxWithExpire(String cacheKey, String value) {
        ResultCode resultCode = tairWrapper.put(cacheKey, value, INIT_VERSION, LOCK_EXPIRE_TIME);
        return ResultCode.SUCCESS.equals(resultCode);

    }


}