Redis transaction - detailed implementation process of seckill case simulation

Concurrent simulation tool ： Use ab Simulation test

CentOS6 Default installation

CentOS7 Manual installation required

Connected to the Internet ：yum install httpd-tools

vim postfile Simulate form submission parameters , With & The end of the symbol ; Store the current directory .

Content ：prodid=0101&

ab -n 2000 -c 200 -k -p ~/postfile -T application/x-www-form-urlencoded http://192.168.2.115:8081/Seckill/doseckill

One 、 Solve the point ： Inventory should be reduced , The number of successful people will increase

Two 、 Oversold problem

  resolvent ： Use optimistic locks to eliminate users

// Add optimistic lock 
jedis.watch(qtkey);
 
//3. Determine inventory 
String qtkeystr = jedis.get(qtkey);
if(qtkeystr==null || "".equals(qtkeystr.trim())) {
System.out.println(" Uninitialized inventory ");
jedis.close();
return false ;
}
 
int qt = Integer.parseInt(qtkeystr);
if(qt<=0) {
System.err.println(" It's been seconds ");
jedis.close();
return false;
}
 
// Add business 
Transaction multi = jedis.multi();
 
//4. reduce stock 
//jedis.decr(qtkey);
multi.decr(qtkey);
 
//5. Add people 
//jedis.sadd(usrkey, uid);
multi.sadd(usrkey, uid);
 
// Perform transactions 
List<Object> list = multi.exec();
 
// Determine whether the transaction commit failed 
if(list==null || list.size()==0) {
System.out.println(" Seckill failure ");
jedis.close();
return false;
}
System.err.println(" Seckill success ");
jedis.close();

 

Solved the oversold problem

 

3、 ... and 、 Connection timeout

Solve through connection pool

 

package com.atguigu;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

public class JedisPoolUtil {
	private static volatile JedisPool jedisPool = null;

	private JedisPoolUtil() {
	}

	public static JedisPool getJedisPoolInstance() {
		if (null == jedisPool) {
			synchronized (JedisPoolUtil.class) {
				if (null == jedisPool) {
					JedisPoolConfig poolConfig = new JedisPoolConfig();
					poolConfig.setMaxTotal(200);
					poolConfig.setMaxIdle(32);
					poolConfig.setMaxWaitMillis(100*1000);
					poolConfig.setBlockWhenExhausted(true);
					poolConfig.setTestOnBorrow(true);  // ping  PONG
				 
					jedisPool = new JedisPool(poolConfig, "192.168.44.168", 6379, 60000 );
				}
			}
		}
		return jedisPool;
	}

	public static void release(JedisPool jedisPool, Jedis jedis) {
		if (null != jedis) {
			jedisPool.returnResource(jedis);
		}
	}

}

 

package com.atguigu;

import java.io.IOException;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
import org.slf4j.LoggerFactory;

import ch.qos.logback.core.rolling.helper.IntegerTokenConverter;
import redis.clients.jedis.HostAndPort;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisCluster;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
import redis.clients.jedis.ShardedJedisPool;
import redis.clients.jedis.Transaction;

/**
 *
 */
public class SecKill_redis {

	public static void main(String[] args) {
		Jedis jedis =new Jedis("192.168.44.168",6379);
		System.out.println(jedis.ping());
		jedis.close();
	}

	// Second kill process 
	public static boolean doSecKill(String uid,String prodid) throws IOException {
		//1 uid and prodid Judge not empty 
		if(uid == null || prodid == null) {
			return false;
		}

		//2  Connect redis
		//Jedis jedis = new Jedis("192.168.44.168",6379);
		// Get through connection pool jedis object 
		JedisPool jedisPoolInstance = JedisPoolUtil.getJedisPoolInstance();
		Jedis jedis = jedisPoolInstance.getResource();

		//3  Splicing key
		// 3.1  stock key
		String kcKey = "sk:"+prodid+":qt";
		// 3.2  Second kill successful users key
		String userKey = "sk:"+prodid+":user";

		// Monitor inventory 
		jedis.watch(kcKey);

		//4  Get inventory , If inventory null, The second kill hasn't started yet 
		String kc = jedis.get(kcKey);
		if(kc == null) {
			System.out.println(" The second kill hasn't started yet , Please wait ");
			jedis.close();
			return false;
		}

		// 5  Judge whether the user repeats the second kill operation 
		if(jedis.sismember(userKey, uid)) {
			System.out.println(" It's a second kill , You can't repeat the second kill ");
			jedis.close();
			return false;
		}

		//6  Judge if the quantity of goods , Inventory quantity is less than 1, End of seckill 
		if(Integer.parseInt(kc)<=0) {
			System.out.println(" The second kill is over ");
			jedis.close();
			return false;
		}

		//7  Second kill process 
		// With a transaction 
		Transaction multi = jedis.multi();

		// Team operation 
		multi.decr(kcKey);
		multi.sadd(userKey,uid);

		// perform 
		List<Object> results = multi.exec();

		if(results == null || results.size()==0) {
			System.out.println(" The second kill failed ....");
			jedis.close();
			return false;
		}

		//7.1  stock -1
		//jedis.decr(kcKey);
		//7.2  Add successful users to the list 
		//jedis.sadd(userKey,uid);

		System.out.println(" The second kill succeeded ..");
		jedis.close();
		return true;
	}
}

1. Link pool parameters
   1. MaxTotal： Control one pool How many can be allocated jedis example , adopt pool.getResource() To get ; If the assignment is -1, It means no limit ; If pool Has been allocated MaxTotal individual jedis example , Now pool The status of is exhausted.
   2. maxIdle： Control one pool How many states are there at most idle( Free ) Of jedis example ;
   3. MaxWaitMillis： Said when borrow One jedis When an instance , Maximum wait milliseconds , If the wait time is exceeded , Throw it directly JedisConnectionException;
   4. testOnBorrow： To obtain a jedis Check the connection availability when the instance is running （ping()）; If true, Obtained jedis Instances are available ;

3、 ... and 、 Inventory remaining problems

It's been seconds , But there are still stocks . reason , Namely Optimistic locks cause many requests to fail . The first order didn't arrive in seconds , The next few seconds may be up . 

resolvent ：LUA Script

Lua It's a small Scripting language ,Lua Scripts can be easily C/C++ Code calls , You can also call... In reverse C/C++ Function of ,Lua There is no powerful library , A complete Lua The interpreter is nothing but 200k, therefore Lua Not suitable as a language for developing standalone applications , But as a Embedded scripting language .

A lot of applications 、 The game uses LUA As its own embedded scripting language , To achieve configurability 、 Extensibility .

This includes the Warcraft map 、 World of warcraft 、 The door of Bode 、 Angry birds and many other game plug-ins or plug-ins .

Lua course _w3cschool

LUA Script in redis Advantages in ：

Will be complex or multi-step redis operation , Write it as a script , Submit to redis perform , Reduce repeated connections redis The number of times . Lifting performance .

LUA The script is similar to redis Business , It has certain atomicity , Will not be interrupted by other orders , You can do some redis Transactional operations .

But notice redis Of lua Script function , Only in Redis 2.6 The above version can only be used .

utilize lua Scripts weed out users , Solve the oversold problem .

redis 2.6 After the version , adopt lua Script solution Competition problem , It's actually redis Take advantage of its single threaded feature , Using task queue to solve the problem of multitask concurrency .

package com.atguigu;

import java.io.IOException;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
import org.slf4j.LoggerFactory;

import ch.qos.logback.core.joran.conditional.ElseAction;
import redis.clients.jedis.HostAndPort;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisCluster;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
import redis.clients.jedis.ShardedJedisPool;
import redis.clients.jedis.Transaction;

public class SecKill_redisByScript {
	
	private static final  org.slf4j.Logger logger =LoggerFactory.getLogger(SecKill_redisByScript.class) ;

	public static void main(String[] args) {
		JedisPool jedispool =  JedisPoolUtil.getJedisPoolInstance();
 
		Jedis jedis=jedispool.getResource();
		System.out.println(jedis.ping());
		
		Set<HostAndPort> set=new HashSet<HostAndPort>();

	//	doSecKill("201","sk:0101");
	}
	
	static String secKillScript ="local userid=KEYS[1];\r\n" + 
			"local prodid=KEYS[2];\r\n" + 
			"local qtkey='sk:'..prodid..\":qt\";\r\n" + 
			"local usersKey='sk:'..prodid..\":usr\";\r\n" + 
			"local userExists=redis.call(\"sismember\",usersKey,userid);\r\n" + 
			"if tonumber(userExists)==1 then \r\n" + 
			"   return 2;\r\n" + 
			"end\r\n" + 
			"local num= redis.call(\"get\" ,qtkey);\r\n" + 
			"if tonumber(num)<=0 then \r\n" + 
			"   return 0;\r\n" + 
			"else \r\n" + 
			"   redis.call(\"decr\",qtkey);\r\n" + 
			"   redis.call(\"sadd\",usersKey,userid);\r\n" + 
			"end\r\n" + 
			"return 1" ;
			 
	static String secKillScript2 = 
			"local userExists=redis.call(\"sismember\",\"{sk}:0101:usr\",userid);\r\n" +
			" return 1";

	public static boolean doSecKill(String uid,String prodid) throws IOException {

		JedisPool jedispool =  JedisPoolUtil.getJedisPoolInstance();
		Jedis jedis=jedispool.getResource();

		 //String sha1=  .secKillScript;
		String sha1=  jedis.scriptLoad(secKillScript);
		Object result= jedis.evalsha(sha1, 2, uid,prodid);

		  String reString=String.valueOf(result);
		if ("0".equals( reString )  ) {
			System.err.println(" Empty ！！");
		}else if("1".equals( reString )  )  {
			System.out.println(" Panic buying ！！！！");
		}else if("2".equals( reString )  )  {
			System.err.println(" The user has robbed ！！");
		}else{
			System.err.println(" Panic buying exception ！！");
		}
		jedis.close();
		return true;
	}
}