Advantages of LUA scripts in Redis
– Write a complex or multi-step redis operation as a script, and submit it to redis for execution at one time, reducing the number of repeated connections to redis. Improve performance.
– LUA scripts are similar to redis transactions, have certain atomicity, will not be queued by other commands, and can complete some redis transactional operations.
– But pay attention to the lua script function of redis, which can only be used in versions above Redis 2.6.
-Use lua scripts to eliminate users and solve the problem of overselling.
SecKillController3
package com.junsang.jedisdemo01.demos.controller;
import com.junsang.jedisdemo01.demos.config.SecKill_redisByScript;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import java.io.IOException;
import java.util.Random;
@RestController
public class SecKillController3 {
@PostMapping(value = "/skv3")
public String skhan(@RequestParam("prodid")String prodid){
try {
String userid = new Random(). nextInt(50000) + "";
boolean b = SecKill_redisByScript.doSecKill(userid, prodid);
System.out.println("second kill result" + b);
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
Jedis connection pool
package com.junsang.jedisdemo01.demos.utils;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
/**
* Jedis connection pool
*/
public class JedisPoolUtils {
//Redis server IP address
private static String ADDR = "10.70.20.47";
//Redis port number
private static int PORT = 6379;
// The maximum number of available connection instances, the default value is 8
// If the assignment is -1, it means no limit
// If the connection pool has allocated maxActive Jedis instances. At this time, the state of the connection pool is exhausted (exhausted)
private static int MAX_ACTIVE = 20;
//Control how many Jedis instances are idle (idle) in a connection pool, and the default value is also 8
private static int MAX_IDLE = 5;
private static int MIN_IOLE = 0;
//The maximum time to wait for an available connection. The unit is milliseconds. The default value is -1, which means never timeout
//If the waiting time is exceeded, JedisConnectionException is thrown directly
private static int MAX_WAIT = -1;
// When allocating a Jedis instance. Whether to perform verification operation in advance
//If true, all Jedis instances obtained are available
private static boolean TEST_ON_BORROW = true;
//Whether to check connection availability (ping()) when returning a Jedis instance to the connection pool
private static boolean TEST_ON_RETURN = true;
private static JedisPool jedisPool = null;
/**
* Initialize the Redis connection pool
*
* @return
*/
public static JedisPool getJedisPoolInstance() {
if (null == jedisPool) {
//sync lock
synchronized(JedisPoolUtils. class) {
if (null == jedisPool) {
//Jedis connection pool configuration
JedisPoolConfig poolConfig = new JedisPoolConfig();
poolConfig.setMaxTotal(MAX_ACTIVE);
poolConfig.setMaxIdle(MAX_IDLE);
poolConfig.setMaxWaitMillis(MAX_WAIT);
poolConfig.setMinIdle(MIN_IOLE);
poolConfig.setTestOnBorrow(TEST_ON_BORROW);
poolConfig.setTestOnReturn(TEST_ON_RETURN);
jedisPool = new JedisPool(poolConfig, ADDR, PORT,1800000,"123456");
}
}
}
return jedisPool;
}
/**
* Get the Jedis instance
*
* @return
*/
public synchronized static Jedis getJedis() {
try {
if (jedisPool != null) {
Jedis resource = jedisPool. getResource();
return resource;
} else {
return null;
}
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
/**
* Release Jedis resources
*
* @param jedis
*/
public static void releaseResource(final Jedis jedis) {
if (jedis != null) {
jedisPool. close();
}
}
public static void main(String[] args) {
JedisPool jedisPool = JedisPoolUtils.getJedisPoolInstance();
JedisPool jedisPool2 = JedisPoolUtils.getJedisPoolInstance();
System.out.println(jedisPool == jedisPool2);
Jedis jedis = null;
try {
jedis = JedisPoolUtils. getJedis();
jedis.set("message", "Redis connection pool");
System.out.println(jedis.get("message"));
} catch (Exception e) {
e.printStackTrace();
} finally {
//Release the Jedis instance
JedisPoolUtils. releaseResource(jedis);
}
}
}
SecKill_redisByScript
package com.junsang.jedisdemo01.demos.config;
import java.io.IOException;
import com.junsang.jedisdemo01.demos.utils.JedisPoolUtils;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
public class SecKill_redisByScript {
static String secKillScript = "local userid=KEYS[1];\r\
" + // define the first variable
"local prodid=KEYS[2];\r\
" + // define the second variable
"local qtkey='sk:'..prodid..":qt";\r\
" + // inventory key
"local usersKey='sk:'..prodid..":usr";\r\
" + // key of the user who successfully kills in seconds
"local userExists=redis.call("sismember",usersKey,userid);\r\
" + //sismember detects whether the key exists in the collection
"if tonumber(userExists)==1 then \r\
" + // If the result of the above line is 1, it means that the user has snapped up, then return 2 directly
" return 2;\r\
" +
"end\r\
" +
"local num= redis.call("get" ,qtkey);\r\
" + // get inventory
"if tonumber(num)<=0 then \r\
" + // if inventory<=0
" return 0;\r\
" + // directly return 0, the inventory is 0, and the rush purchase is empty
"else \r\
" +
" redis.call("decr",qtkey);\r\
" + // inventory -1
" redis.call("sadd",usersKey,userid);\r\
" + // user + 1
"end\r\
" +
"return 1";
static String secKillScript2 =
"local userExists=redis.call("sismember","{sk}:0101:usr",userid);\r\
" +
"return 1";
/**
* Serious spike function
* @param uid
* @param prodid
* @return
* @throws IOException
*/
public static boolean doSecKill(String uid,String prodid) throws IOException {
JedisPool jedispool = JedisPoolUtils.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("Already sold out!!");
}else if("1".equals( reString ) ) {
System.out.println("Purchase success!!!");
}else if("2". equals( reString ) ) {
System.err.println("The user has robbed!!");
}else{
System.err.println("Purchasing exception!!");
}
jedis. close();
return true;
}
}
