PHP uses redis transaction to realize commodity spike

One 、 Business

1、 Open transaction   multi        

2、 Perform transactions exec

3、 Discard transaction  discard

notes ： The following two cases ,

        a. If there is an error in a command during the execution of the transaction queue , The entire transaction command queue will be discarded

        b. There is no error in joining the queue , An error is reported when executing a command , Other commands will be executed successfully .（ Non atomicity ）

  Two 、 Pessimistic lock and optimistic lock

1、 Pessimistic locking

Pessimistic locking (Pessimistic Lock), seeing the name of a thing one thinks of its function , Is very pessimistic , Every time I go to get the data, I think others will modify it , So every time I get the data, I lock it , So that if people want to take this data, they will block Until it gets the lock . There are many lock mechanisms used in traditional relational databases , For example, line locks. , Table lock, etc. , Read the lock , Write locks, etc. , It's all locked before the operation .

2、 Optimism lock

Optimism lock (Optimistic Lock), seeing the name of a thing one thinks of its function , Is very optimistic , Every time I go to get the data, I think other people won't modify it , So it won't lock , But in the process of updating, we will judge whether other people have updated this data during this period , You can use mechanisms like version numbers . Optimistic lock is suitable for multi read applications , This can improve throughput .Redis It's using this check-and-set The mechanism implements the .

scene ： Grab tickets .

Here's an example ： Left client settings sign=10, In execution multi Before , Execute first watch key1 [key2], You can watch one ( Or more ) key, If before the transaction is executed ( Or these ) key Altered by other orders , Then the business will be interrupted .· You can see that the coordinates are set to 20 succeed , Right side setting 30 You don't succeed .

notes ：unwatch, Cancel surveillance

  3、 ... and 、 utilize redis Realize the second kill function

The code is as follows

<?php
class RedisPool
{
    private static $connections = array(); // Define an object pool
    private static $servers = array(); // Definition redis The configuration file Contains all the redis The server
    public static function addServer($conf) // Definition add redis Configuration method
    {
        foreach ($conf as $alias => $data){
            self::$servers[$alias]=$data;
        }
    }
 
    public static function getRedis($alias,$select = 0)// Two parameters: the server to be connected KEY, Library to select
    {
        if(!array_key_exists($alias,self::$connections)){  // Judge whether there is in the connection pool
            $redis = new \Redis();
            $redis->connect(self::$servers[$alias][0],self::$servers[$alias][1]);
            self::$connections[$alias]=$redis;
            if(isset(self::$servers[$alias][2]) && self::$servers[$alias][2]!=""){
                self::$connections[$alias]->auth(self::$servers[$alias][2]);
            }
        }
        self::$connections[$alias]->select($select);
        return self::$connections[$alias];
    }
}
 
function connect_to_redis()
{
    // Use redis Connection pool
    $conf = array(
        'RA' => array('127.0.0.1','6379')   // Definition Redis To configure
    );
    RedisPool::addServer($conf); // add to Redis To configure
    $redis = RedisPool::getRedis('RA',1); // Connect RA, Use the default 0 library
    return $redis;
}
$user_id = rand(100,999);
$redis = connect_to_redis();
// Monitor inventory
$redis->watch(['goods_num']);
$goods_num = $redis->get('goods_num');
if ($goods_num <= 0){
    echo " No stock ";
    return 1;
}
// The number
$redis->multi();
$redis->DECR('goods_num', 1);
// Buyers join the queue
$redis->lPush('users', $user_id);
$status = $redis->exec();
// // If it fails, cancel the transaction
if (!$status) {
    $redis->discard();
}

Of course, they are all tested in Gaohe

Use ab Pressure measuring tool
ab -n 500 -c 30 http://re.com/re.php

This code solves the following problems ：

1、 Oversold -redis Business + Optimism lock + Inventory monitoring
2、redis Connection timeout -redis Connection pool

But there's a problem ： When the total number of requests -n Is precisely 50 There was a problem left over from inventory , To solve this problem , We use it LUA Script to achieve

3、 Inventory remaining problems -LUA foot

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 Scripts solve the scramble problem , It's actually redis Take advantage of its single threaded feature , Using task queue to solve the problem of multitask concurrency ."

<?php
class RedisPool
{
    private static $connections = array(); // Define an object pool
    private static $servers = array(); // Definition redis The configuration file Contains all the redis The server
    public static function addServer($conf) // Definition add redis Configuration method
    {
        foreach ($conf as $alias => $data){
            self::$servers[$alias]=$data;
        }
    }
 
    public static function getRedis($alias,$select = 0)// Two parameters: the server to be connected KEY, Library to select
    {
        if(!array_key_exists($alias,self::$connections)){  // Judge whether there is in the connection pool
            $redis = new \Redis();
            $redis->connect(self::$servers[$alias][0],self::$servers[$alias][1]);
            self::$connections[$alias]=$redis;
            if(isset(self::$servers[$alias][2]) && self::$servers[$alias][2]!=""){
                self::$connections[$alias]->auth(self::$servers[$alias][2]);
            }
        }
        self::$connections[$alias]->select($select);
        return self::$connections[$alias];
    }
}
 
function connect_to_redis()
{
    // Use redis Connection pool
    $conf = array(
        'RA' => array('47.95.33.138','6379')   // Definition Redis To configure
    );
    RedisPool::addServer($conf); // add to Redis To configure
    $redis = RedisPool::getRedis('RA',1); // Connect RA, Use the default 0 library
    return $redis;
}
$user_id = rand(100,999);
$redis = connect_to_redis();

$lua = <<<LUA
    local num = redis.call("get", 'goods_num')
    if tonumber(num)<=0 then
        return 0
    else
        redis.call("decr", 'goods_num')
        redis.call("lpush", 'users', KEYS[1])
    end
    return 1
LUA;

$l = <<<LUA
    redis.call("lpush", 'users', KEYS[1])
    return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}
LUA;
$s = $redis->eval($lua,array($user_id),1);
if ($s == 0){
    echo " The second kill is over ";
}else{
    echo " Congratulations on the success of secsha ";
}

ab -n 50 -c 30 http://re.com/re.php 

  This is the second kill , The above code solves several key problems in seckill ：redis Connection timeout , Sell less 、 Overbought problem , Of course, there will be other problems in the actual production process , If you encounter a welcome message to discuss .