Redismission inventory deduction demo

        In a distributed scenario , To realize the lock, if only through Synchronized Keywords don't work , because Synchronized It's just here java Locked in the process . To implement distributed locks, you can use redission. In this paper nginx Reverse proxy +redission Realize inventory deduction demo.

Introduce dependencies

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.redisson</groupId>
			<artifactId>redisson</artifactId>
			<version>3.10.6</version>
		</dependency>

@Configuration
public class RedisConfig {

    @Bean
    public RedissonClient getRedisClient() {
        Config config = new Config();
        config.useSingleServer().setAddress("redis://127.0.0.1:6379").setPassword("123456");
        return Redisson.create(config);
    }

}

@RestController
public class RedissionController {

    @Autowired
    RedissonClient redissonClient;
    
    @GetMapping(value = "/getLock")
    public String getLock() {
        String lockKey = "lock";
        String key = "shopKey";
        RLock lock = redissonClient.getLock(lockKey);
        try {
            lock.lock();
            RBucket<String> bucket = redissonClient.getBucket(key);
            int stock = Integer.parseInt(bucket.get());
            if (stock > 0) {
                int realStock = stock - 1;
                bucket.set(String.valueOf(realStock));
                System.out.println(" Successful sale , The remaining ："+ realStock);
                return "success";
            }else{
                System.out.println(" The surplus stock is insufficient ");
                return "fail";
            }
        } finally {
            lock.unlock();
        }

    }

}

operation redis There are many kinds of clients （jedis,lettuce,redission contrast ）, Officially recommended java Client such as jedis,springboot2.0 Default adopted lettuce, as well as redission, Here we directly adopt redission. And use redission It should be noted that bucket Concept ,RBucket Object is a general object bucket, which can be used to store any type of object , Its bottom layer is by default FstCodec Serialize storage , Because you need to go in advance redis Input inside 50 stock , If direct set shopKey 50 , When calling redissonClient.getBucket(key), The following exceptions will occur , Because the types before and after serialization are inconsistent .

2019-05-15 13:39:59.973 [redisson-netty-2-3] ERROR o.r.c.h.CommandDecoder [decodeCommand:203]     - Unable to decode data. channel: [id: 0x477c5ced, L:/192.168.4.94:57423 - R:10.10.10.43/10.10.10.43:6379], reply: ReplayingDecoderByteBuf(ridx=102, widx=102), command: (GET), params: [Geek:xxxxx:xxxx]
java.io.IOException: java.lang.NullPointerException
    at org.nustaq.serialization.FSTObjectInput.readObject(FSTObjectInput.java:247)
    at org.redisson.codec.FstCodec$1.decode(FstCodec.java:228)
    at org.redisson.client.handler.CommandDecoder.decode(CommandDecoder.java:368)
    at org.redisson.client.handler.CommandDecoder.decodeCommand(CommandDecoder.java:200)
    at org.redisson.client.handler.CommandDecoder.decode(CommandDecoder.java:140)
    at org.redisson.client.handler.CommandDecoder.decode(CommandDecoder.java:115)
    at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:502)
    at io.netty.handler.codec.ReplayingDecoder.callDecode(ReplayingDecoder.java:366)
    at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:278)

There are two solutions

1. One is to insert the serialized result directly So called redissonClient.getBucket(key) The deserialization type is also consistent
set shopKey "\xfc\x0250"

​​​​​​​2. One is to set bucket Serialization mode and then set
​​​​​​​redissonClient.getBucket(key, new StringCodec());
​​​​​​​set shopKey 50

nginx To configure   Most of them can be configured by default , The changes that need to be made have been approved  # // Mark it out , After configuration, use the configuration file to start it .  

Start command -c Indicates that the following configuration file is used when starting , It can also be used before startup -t Command to test whether the configuration is successful , If the configuration is successful xx.conf test is successful, And then it starts .

/usr/local/Cellar/nginx/1.21.1/bin/nginx  -c /usr/local/Cellar/nginx/1.21.1/.bottle/etc/nginx/nginx.conf

#user  nobody;
worker_processes  1;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;

    #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
    #                  '$status $body_bytes_sent "$http_referer" '
    #                  '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    #gzip  on;
    
    # //  Achieve a load balancing  8081,8082 Ports are accessed in turn 
    upstream redisLock{
     server 10.254.2.27:8081 weight=1; #ipV4, adopt ipconfig Command view 
     server 10.254.2.27:8082 weight=1;
    }
 
    server {
        listen       80;
        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

        location / {
            root   html;
            index  index.html index.htm;
           # //  Forward to the configured upstream
            proxy_pass   http://redisLock;
        }

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

        # proxy the PHP scripts to Apache listening on 127.0.0.1:80
        #
        #location ~ \.php$ {
        #    proxy_pass   http://127.0.0.1;
        #}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        #location ~ \.php$ {
        #    root           html;
        #    fastcgi_pass   127.0.0.1:9000;
        #    fastcgi_index  index.php;
        #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
        #    include        fastcgi_params;
        #}

        # deny access to .htaccess files, if Apache's document root
        # concurs with nginx's one
        #
        #location ~ /\.ht {
        #    deny  all;
        #}
    }


    # another virtual host using mix of IP-, name-, and port-based configuration
    #
    #server {
    #    listen       8000;
    #    listen       somename:8080;
    #    server_name  somename  alias  another.alias;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}


    # HTTPS server
    #
    #server {
    #    listen       443 ssl;
    #    server_name  localhost;

    #    ssl_certificate      cert.pem;
    #    ssl_certificate_key  cert.key;

    #    ssl_session_cache    shared:SSL:1m;
    #    ssl_session_timeout  5m;

    #    ssl_ciphers  HIGH:!aNULL:!MD5;
    #    ssl_prefer_server_ciphers  on;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}
    include servers/*;
}

then idea To start, respectively, 8081,8082 Two ports , And then visit http://127.0.0.1/getLock that will do , Here you can use jmeter and postman Simulate concurrent requests .