#27 stock: race condition solution 2 - db(named lock)

stock/src/main/java/com/example/stock/facade/NamedLockStockFacade.java

@@ -0,0 +1,26 @@
+package com.example.stock.facade;
+
+import com.example.stock.repository.LockRepository;
+import com.example.stock.service.StockService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Transactional;
+
+@Component
+@RequiredArgsConstructor
+public class NamedLockStockFacade {
+
+    private final LockRepository lockRepository;
+
+    private final StockService stockService;
+
+    @Transactional
+    public void decrease(Long id, Long quantity) {
+        try {
+            lockRepository.getLock(id.toString());
+            stockService.decreaseNewTransaction(id, quantity);
+        } finally {
+            lockRepository.releaseLock(id.toString());
+        }
+    }
+}

stock/src/main/java/com/example/stock/repository/LockRepository.java

@@ -0,0 +1,14 @@
+package com.example.stock.repository;
+
+import com.example.stock.domain.Stock;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+
+public interface LockRepository extends JpaRepository<Stock, Long> {
+
+    @Query(value = "select get_lock(:key, 3000)", nativeQuery = true)
+    void getLock(String key);
+
+    @Query(value = "select release_lock(:key)", nativeQuery = true)
+    void releaseLock(String key);
+}

stock/src/main/java/com/example/stock/service/StockService.java

@@ -4,6 +4,7 @@ import com.example.stock.domain.Stock;
 import com.example.stock.repository.StockRepository;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Propagation;
 import org.springframework.transaction.annotation.Transactional;
 
 @Service
@@ -23,4 +24,16 @@ public class StockService {
         // 저장
         stockRepository.saveAndFlush(stock);
     }
+
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    public void decreaseNewTransaction(Long id, Long quantity) {
+        // 재고 조회
+        Stock stock = stockRepository.findById(id).orElseThrow();
+
+        // 재고 감소
+        stock.decrease(quantity);
+
+        // 저장
+        stockRepository.saveAndFlush(stock);
+    }
 }

stock/src/main/resources/application.yml

@@ -8,6 +8,8 @@ spring:
     url: jdbc:mysql://127.0.0.1:13306/stock_example
     username: root
     password: 1234
+    hikari:
+      maximum-pool-size: 40
 
 logging:
   level:

stock/src/test/java/com/example/stock/facade/NamedLockStockFacadeTest.java

@@ -0,0 +1,61 @@
+package com.example.stock.facade;
+
+import com.example.stock.domain.Stock;
+import com.example.stock.repository.StockRepository;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@SpringBootTest
+class NamedLockStockFacadeTest {
+    @Autowired
+    private NamedLockStockFacade namedLockStockFacade;
+
+    @Autowired
+    private StockRepository stockRepository;
+
+    @BeforeEach
+    public void before() {
+        Stock stock = new Stock(1L, 100L);
+
+        stockRepository.saveAndFlush(stock);
+    }
+
+    @AfterEach
+    public void after() {
+        stockRepository.deleteAll();
+    }
+
+    @Test
+    public void 동시에_100개의_요청_named_lock() throws InterruptedException {
+        int threadCount = 100;
+        ExecutorService executorService = Executors.newFixedThreadPool(32);
+
+        CountDownLatch latch = new CountDownLatch(threadCount);
+
+        for (int i = 0; i < threadCount; i++) {
+            executorService.submit(() -> {
+                try {
+                    namedLockStockFacade.decrease(1L, 1L);
+                } finally {
+                    latch.countDown();
+                }
+            });
+        }
+
+        latch.await();
+
+        Stock stock = stockRepository.findById(1L).orElseThrow();
+
+        // 100 - (1 * 100) = 0
+        assertEquals(0L, stock.getQuantity());
+    }
+}