♻️ refactor: fcm 토큰 upsert할 때 Redis Lua Script 사용

Author: strongmhk

gradlew

@@ -1,19 +1,41 @@
 package akuma.whiplash.infrastructure.redis;
 
-import java.util.Objects;
+import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 import lombok.RequiredArgsConstructor;
-import org.springframework.dao.DataAccessException;
-import org.springframework.data.redis.core.RedisOperations;
 import org.springframework.data.redis.core.RedisTemplate;
-import org.springframework.data.redis.core.SessionCallback;
+import org.springframework.data.redis.core.script.RedisScript;
 import org.springframework.stereotype.Service;
 
 @Service
 @RequiredArgsConstructor
 public class RedisService {
 
+    private static final RedisScript<Long> REMOVE_DEVICE_SCRIPT = RedisScript.of("""
+        local oldToken = redis.call('GET', KEYS[1])
+        if not oldToken or oldToken == '' then
+            redis.call('DEL', KEYS[1])
+            return 0
+        end
+        redis.call('SREM', KEYS[2], oldToken)
+        redis.call('DEL', 'fcm:token:' .. oldToken .. ':device')
+        redis.call('DEL', KEYS[1])
+        return 1
+        """, Long.class);
+
+    private static final RedisScript<Long> UPSERT_SCRIPT = RedisScript.of("""
+        local oldToken = redis.call('GET', KEYS[1])
+        if oldToken and oldToken ~= '' and oldToken ~= ARGV[1] then
+            redis.call('SREM', KEYS[2], oldToken)
+            redis.call('DEL', 'fcm:token:' .. oldToken .. ':device')
+        end
+        redis.call('SET', KEYS[1], ARGV[1])
+        redis.call('SET', 'fcm:token:' .. ARGV[1] .. ':device', ARGV[2])
+        redis.call('SADD', KEYS[2], ARGV[1])
+        return 1
+        """, Long.class);
+
     private final RedisTemplate<String, String> redisTemplate;
 
     public Set<String> getFcmTokens(Long memberId) {
@@ -30,43 +52,25 @@ public void removeInvalidToken(Long memberId, String token) {
 
     /**
      * deviceId에 새 fcmToken을 등록(upsert).
-     * - 같은 토큰 재등록이면 idempotent하게 Set/매핑 보강만 함
      * - 다른 토큰으로 교체되면 이전 토큰을 member Set에서 제거하고 매핑 정리
+     * - 같은 토큰 재등록이면 idempotent하게 처리됨
      *
-     * 참고: MULTI/EXEC 트랜잭션을 쓰므로 RedisTemplate에 transactionSupport=true 필요.
+     * Lua 스크립트로 GET-SREM-DEL-SET-SADD를 단일 원자적 명령으로 실행한다.
      */
     public void upsertFcmToken(Long memberId, String deviceId, String newToken) {
-        String deviceKey = keyDeviceToToken(deviceId);
-        String memberSetKey = keyMemberTokens(memberId);
-        String newTokenMapKey = keyTokenToDevice(newToken);
-
-        String oldToken = redisTemplate.opsForValue().get(deviceKey);
-
-        // 1) 동일 토큰 재등록: idempotent 보강
-        if (Objects.equals(oldToken, newToken)) {
-            redisTemplate.opsForSet().add(memberSetKey, newToken);
-            redisTemplate.opsForValue().set(newTokenMapKey, deviceId);
-            return;
+        if (deviceId == null || deviceId.isBlank()) {
+            throw new IllegalArgumentException("deviceId must not be null or blank");
+        }
+        if (newToken == null || newToken.isBlank()) {
+            throw new IllegalArgumentException("newToken must not be null or blank");
         }
 
-        // 2) 토큰 교체: 원자적 멀티 실행
-        redisTemplate.execute(new SessionCallback<Void>() {
-            @Override
-            public Void execute(RedisOperations operations) throws DataAccessException {
-                operations.multi();
-                // 이전 토큰 정리
-                if (oldToken != null && !oldToken.isBlank()) {
-                    operations.opsForSet().remove(memberSetKey, oldToken);
-                    operations.delete(keyTokenToDevice(oldToken));
-                }
-                // 신규 매핑/등록
-                operations.opsForValue().set(deviceKey, newToken);
-                operations.opsForValue().set(newTokenMapKey, deviceId);
-                operations.opsForSet().add(memberSetKey, newToken);
-                operations.exec();
-                return null;
-            }
-        });
+        redisTemplate.execute(
+            UPSERT_SCRIPT,
+            List.of(keyDeviceToToken(deviceId), keyMemberTokens(memberId)),
+            newToken,
+            deviceId
+        );
     }
 
     // ===== 선택: 특정 디바이스 로그아웃 시 정리 =====
@@ -75,26 +79,10 @@ public Void execute(RedisOperations operations) throws DataAccessException {
      * 특정 deviceId에 매핑된 토큰을 제거하고, member Set에서도 제거.
      */
     public void removeFcmTokenForDevice(Long memberId, String deviceId) {
-        String deviceKey = keyDeviceToToken(deviceId);
-        String memberSetKey = keyMemberTokens(memberId);
-
-        String oldToken = redisTemplate.opsForValue().get(deviceKey);
-        if (oldToken == null || oldToken.isBlank()) {
-            redisTemplate.delete(deviceKey);
-            return;
-        }
-
-        redisTemplate.execute(new SessionCallback<Void>() {
-            @Override
-            public Void execute(RedisOperations operations) throws DataAccessException {
-                operations.multi();
-                operations.opsForSet().remove(memberSetKey, oldToken);
-                operations.delete(keyTokenToDevice(oldToken));
-                operations.delete(deviceKey);
-                operations.exec();
-                return null;
-            }
-        });
+        redisTemplate.execute(
+            REMOVE_DEVICE_SCRIPT,
+            List.of(keyDeviceToToken(deviceId), keyMemberTokens(memberId))
+        );
     }
 
     // ===== 선택: 조회 유틸 =====

src/main/java/akuma/whiplash/infrastructure/redis/RedisService.java

@@ -2,9 +2,11 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
-import static org.junit.jupiter.api.Assertions.*;
 
 import akuma.whiplash.common.config.RedisContainerInitializer;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
@@ -82,5 +84,42 @@ void fail_tokenNull() {
             assertThatThrownBy(() -> redisService.upsertFcmToken(1L, "device", null))
                 .isInstanceOf(IllegalArgumentException.class);
         }
+
+        @Test
+        @DisplayName("성공: 동일 deviceId에 동시 요청이 와도 tokenCount가 1이다")
+        void success_concurrentUpsertKeepsOneToken() throws InterruptedException {
+            // given
+            Long memberId = 1L;
+            String deviceId = "shared-device";
+            int threadCount = 10;
+
+            ExecutorService executor = Executors.newFixedThreadPool(threadCount);
+            CountDownLatch ready = new CountDownLatch(threadCount);
+            CountDownLatch start = new CountDownLatch(1);
+            CountDownLatch done = new CountDownLatch(threadCount);
+
+            for (int i = 0; i < threadCount; i++) {
+                final String token = "token-" + i;
+                executor.submit(() -> {
+                    ready.countDown();
+                    try {
+                        start.await();
+                        redisService.upsertFcmToken(memberId, deviceId, token);
+                    } catch (InterruptedException e) {
+                        Thread.currentThread().interrupt();
+                    } finally {
+                        done.countDown();
+                    }
+                });
+            }
+
+            ready.await();
+            start.countDown();
+            done.await();
+            executor.shutdown();
+
+            // then
+            assertThat(redisService.getFcmTokens(memberId)).hasSize(1);
+        }
     }
 }