[feat/#13]: Local Caching을 통해 트래픽이 Redis 네트워크를 타지 않고 자바단에서 차단되도록 구현한다

coupon-api/build.gradle.kts

@@ -21,6 +21,9 @@ dependencies {
     implementation("org.springframework.boot:spring-boot-starter-data-redis")
     implementation("org.redisson:redisson-spring-boot-starter:3.25.0")
 
+    // Cache
+    implementation("com.github.ben-manes.caffeine:caffeine")
+
     // Monitoring
     implementation("org.springframework.boot:spring-boot-starter-actuator")
     implementation("io.micrometer:micrometer-registry-prometheus")

coupon-api/src/main/kotlin/com/woong2e/couponsystem/coupon/application/service/impl/AsyncLuaCouponIssueService.kt

@@ -3,6 +3,7 @@ package main.kotlin.com.woong2e.couponsystem.coupon.application.service.impl
 import main.kotlin.com.woong2e.couponsystem.coupon.application.port.out.CouponIssueEventPublisher
 import main.kotlin.com.woong2e.couponsystem.coupon.application.response.CouponIssueResponse
 import main.kotlin.com.woong2e.couponsystem.coupon.application.service.CouponIssueService
+import main.kotlin.com.woong2e.couponsystem.coupon.infra.cache.LocalCouponCacheManager
 import main.kotlin.com.woong2e.couponsystem.coupon.infra.redis.CouponRedisRepository
 import main.kotlin.com.woong2e.couponsystem.coupon.status.CouponErrorStatus
 import main.kotlin.com.woong2e.couponsystem.global.exception.CustomException
@@ -13,19 +14,28 @@ import java.util.UUID
 @Service("asyncLua")
 class AsyncLuaCouponIssueService(
     private val couponRedisRepository: CouponRedisRepository,
-    private val couponIssueEventPublisher: CouponIssueEventPublisher
+    private val couponIssueEventPublisher: CouponIssueEventPublisher,
+    private val localCouponCacheManager: LocalCouponCacheManager,
 ) : CouponIssueService {
 
     override fun issue(couponId: UUID, userId: Long): CouponIssueResponse {
-        val result = couponRedisRepository.issueRequest(couponId.toString(), userId)
+        val key = couponId.toString()
 
-        when (result) {
-            "DUPLICATED" -> throw CustomException(CouponErrorStatus.COUPON_ALREADY_ISSUED)
-            "SOLD_OUT" -> throw CustomException(CouponErrorStatus.COUPON_OUT_OF_STOCK)
+        if (localCouponCacheManager.isSoldOut(key)) {
+            throw CustomException(CouponErrorStatus.COUPON_OUT_OF_STOCK)
+        }
+
+        val result = couponRedisRepository.issueRequest(key, userId)
+
+        return when (result) {
             "SUCCESS" -> {
                 couponIssueEventPublisher.publish(couponId, userId)
-
-                return CouponIssueResponse.asyncIssued()
+                CouponIssueResponse.asyncIssued()
+            }
+            "DUPLICATED" -> throw CustomException(CouponErrorStatus.COUPON_ALREADY_ISSUED)
+            "SOLD_OUT" -> {
+                localCouponCacheManager.putSoldOut(key)
+                throw CustomException(CouponErrorStatus.COUPON_OUT_OF_STOCK)
             }
             else -> throw CustomException(ErrorStatus.SYSTEM_BUSY)
         }

coupon-api/src/main/kotlin/com/woong2e/couponsystem/coupon/infra/cache/LocalCouponCacheManager.kt

@@ -0,0 +1,23 @@
+package main.kotlin.com.woong2e.couponsystem.coupon.infra.cache
+
+import com.github.benmanes.caffeine.cache.Cache
+import com.github.benmanes.caffeine.cache.Caffeine
+import org.springframework.stereotype.Component
+import java.util.concurrent.TimeUnit
+
+@Component
+class LocalCouponCacheManager {
+
+    private val cache: Cache<String, Boolean> = Caffeine.newBuilder()
+        .expireAfterWrite(10, TimeUnit.MINUTES) // 10분 후 만료
+        .maximumSize(1000)                      // 최대 1000개 쿠폰 키 보관
+        .build()
+
+    fun putSoldOut(couponId: String) {
+        cache.put(couponId, true)
+    }
+
+    fun isSoldOut(couponId: String): Boolean {
+        return cache.getIfPresent(couponId) == true
+    }
+}