SecKillProject

Backend Restful API simulates handling high concurrent QPS by using multithreading and caching

Project Status

Under maintain

• Completed: User management
• Completed: Order service (single thread)
• Completed: Implemented Redis caching
• Completed: Implemented multi-thread to handle high incoming queries

Tech Stack

• Springboot + Redis + MySQL
• JMeter

Handling High Concurrent Incoming Queries

• Using @Async and ThreadPoolTaskExecutor to complete background tasks asynchronously.
• Using Redis caching to prevent high IO pressure for MySQL database.
• Using Synchronize() keyword to ensure thread-safety.
• Using Jmeter to simulate concurrent queries.

JMeter Testing

• Setting for concurrent queries (1000 users)
• HTTP request to api
• Merchandise stock counts (Only 10 stock available)
• Issue: oversold
  
  
• Analyze: Since tasks are running under multiple threads, we need to guarantee that stock=stock-1 is atomic

Merchandise item = (Merchandise) redisTemplate.boundHashOps(Merchandise.class.getSimpleName()).get(Integer.toString(orderRecord.getMerchandise_id()));
                if(item != null){
                    if(item.getMerchandise_stock()>0){
                        item.setMerchandise_stock(item.getMerchandise_stock() - 1); //NOT ATMOIC STATEMENT
                        redisTemplate.boundHashOps(Merchandise.class.getSimpleName()).put(Integer.toString(item.getMerchandise_id()), item);
                        redisTemplate.boundHashOps(OrderInfo.class.getSimpleName()).put(LocalTime.now()+Integer.toString(orderRecord.getUser_id()), orderInfo);

                    }
                }

• Solution: Using synchronize keyword to ensure the block of code is executed all in one.

synchronized (OrderThread.class) {
                Merchandise item = (Merchandise) redisTemplate.boundHashOps(Merchandise.class.getSimpleName()).get(Integer.toString(orderRecord.getMerchandise_id()));
                if(item != null){
                    if(item.getMerchandise_stock()>0){
                        item.setMerchandise_stock(item.getMerchandise_stock() - 1);
                        redisTemplate.boundHashOps(Merchandise.class.getSimpleName()).put(Integer.toString(item.getMerchandise_id()), item);
                        redisTemplate.boundHashOps(OrderInfo.class.getSimpleName()).put(LocalTime.now()+Integer.toString(orderRecord.getUser_id()), orderInfo);

                    }
                }
            }

• Only 10 items are sold
  
  
• Other possible solution: Using optimistic locking, ex: CAS with version

Setup MySQL and Redis

Install MySQL and Redis
Locate application.properties

spring.datasource.url= {MYSQL connection url}
spring.datasource.username= {Username}
spring.datasource.password= {Password}
spring.redis.host=127.0.0.1
spring.redis.port={port}
redis.config.host=redis://127.0.0.1:{port}

API Usage

See comments in src/main/java/com.learning.SecKillProject/SecKillProject.java