feat: Redis Cache Aside 리다이렉트 조회 적용

build.gradle

@@ -26,6 +26,7 @@ dependencies {
 	// Database
 	implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
 	runtimeOnly 'com.mysql:mysql-connector-j'
+	implementation 'org.springframework.boot:spring-boot-starter-data-redis'
 
 	// Monitoring
 	implementation 'org.springframework.boot:spring-boot-starter-actuator'

docker-compose.yml

@@ -17,9 +17,14 @@ services:
       SPRING_DATASOURCE_USERNAME: ${DB_USERNAME:-url_shortener}
       SPRING_DATASOURCE_PASSWORD: ${DB_PASSWORD:?DB_PASSWORD is required}
 
+      SPRING_DATA_REDIS_HOST: redis
+      SPRING_DATA_REDIS_PORT: 6379
+
     depends_on:
       mysql:
         condition: service_healthy
+      redis:
+        condition: service_healthy
 
     healthcheck:
       test:
@@ -113,7 +118,20 @@ services:
       app:
         condition: service_healthy
 
+  redis:
+    image: redis:7.4-alpine
+    ports:
+      - "${REDIS_PORT:-6379}:6379"
+    healthcheck:
+      test: [ "CMD", "redis-cli", "ping" ]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+    volumes:
+      - redis-data:/data
+
 volumes:
   mysql-data:
   prometheus-data:
-  grafana-data:
+  grafana-data:
+  redis-data:

src/main/java/com/backendsystemdesignlab/urlshortener/cache/ShortUrlCache.java

@@ -0,0 +1,32 @@
+package com.backendsystemdesignlab.urlshortener.cache;
+
+import org.springframework.data.redis.core.StringRedisTemplate;
+import org.springframework.stereotype.Component;
+
+import java.time.Duration;
+import java.util.Optional;
+
+@Component
+public class ShortUrlCache {
+
+    private static final String KEY_PREFIX = "short-url:";
+    private static final Duration TTL = Duration.ofHours(1);
+
+    private final StringRedisTemplate redisTemplate;
+
+    public ShortUrlCache(StringRedisTemplate redisTemplate) {
+        this.redisTemplate = redisTemplate;
+    }
+
+    public Optional<String> find(String shortCode) {
+        String longUrl = redisTemplate.opsForValue()
+                .get(KEY_PREFIX +  shortCode);
+
+        return Optional.ofNullable(longUrl);
+    }
+
+    public void save(String shortCode, String longUrl) {
+        redisTemplate.opsForValue()
+                .set(KEY_PREFIX + shortCode, longUrl, TTL);
+    }
+}

src/main/java/com/backendsystemdesignlab/urlshortener/controller/RedirectController.java

@@ -1,5 +1,6 @@
 package com.backendsystemdesignlab.urlshortener.controller;
 
+import com.backendsystemdesignlab.urlshortener.service.RedirectService;
 import com.backendsystemdesignlab.urlshortener.service.ShortUrlService;
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.HttpStatus;
@@ -16,13 +17,13 @@
 @RequestMapping("/api/v1")
 public class RedirectController {
 
-    private final ShortUrlService shortUrlService;
+    private final RedirectService redirectService;
 
     @GetMapping("/{shortCode}")
     public ResponseEntity<Void> redirect(
             @PathVariable String shortCode
     ) {
-        String longUrl = shortUrlService.getLongUrl(shortCode);
+        String longUrl = redirectService.findLongUrl(shortCode);
 
         return ResponseEntity
                 .status(HttpStatus.FOUND) // 302 FOUND

src/main/java/com/backendsystemdesignlab/urlshortener/exception/ShortUrlNotFoundException.java

@@ -0,0 +1,12 @@
+package com.backendsystemdesignlab.urlshortener.exception;
+
+public class ShortUrlNotFoundException extends RuntimeException {
+
+    public ShortUrlNotFoundException() {
+        super("단축 URL을 찾을 수 없습니다.");
+    }
+
+    public ShortUrlNotFoundException(String shortCode) {
+        super("단축 URL을 찾을 수 없습니다. shortCode=" + shortCode);
+    }
+}

src/main/java/com/backendsystemdesignlab/urlshortener/service/RedirectService.java

@@ -0,0 +1,36 @@
+package com.backendsystemdesignlab.urlshortener.service;
+
+import com.backendsystemdesignlab.urlshortener.cache.ShortUrlCache;
+import com.backendsystemdesignlab.urlshortener.encoding.Base62Encoder;
+import com.backendsystemdesignlab.urlshortener.exception.ShortUrlNotFoundException;
+import com.backendsystemdesignlab.urlshortener.url.domain.ShortUrl;
+import com.backendsystemdesignlab.urlshortener.url.repository.ShortUrlRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.stereotype.Service;
+import org.springframework.web.server.ResponseStatusException;
+
+@Service
+@RequiredArgsConstructor
+public class RedirectService {
+
+    private final ShortUrlRepository shortUrlRepository;
+    private final ShortUrlCache shortUrlCache;
+    private final Base62Encoder base62Encoder;
+
+    public String findLongUrl(String shortCode) {
+        return shortUrlCache.find(shortCode)
+                .orElseGet(() -> findFromDatabase(shortCode));
+    }
+
+    private String findFromDatabase(String shortCode) {
+        long id = base62Encoder.decode(shortCode);
+
+        ShortUrl shortUrl = shortUrlRepository.findById(id)
+                .orElseThrow(() -> new ShortUrlNotFoundException(shortCode));
+
+        shortUrlCache.save(shortCode, shortUrl.getLongUrl());
+
+        return shortUrl.getLongUrl();
+    }
+}

src/main/java/com/backendsystemdesignlab/urlshortener/service/ShortUrlService.java

@@ -1,6 +1,7 @@
 package com.backendsystemdesignlab.urlshortener.service;
 
 import com.backendsystemdesignlab.urlshortener.encoding.Base62Encoder;
+import com.backendsystemdesignlab.urlshortener.exception.ShortUrlNotFoundException;
 import com.backendsystemdesignlab.urlshortener.url.domain.ShortUrl;
 import com.backendsystemdesignlab.urlshortener.url.repository.ShortUrlRepository;
 import lombok.RequiredArgsConstructor;
@@ -36,19 +37,12 @@ public String getLongUrl(String shortCode) {
         try {
             id = base62Encoder.decode(shortCode);
         } catch (IllegalArgumentException | ArithmeticException exception) {
-            throw shortUrlNotFoundException();
+            throw new ShortUrlNotFoundException();
         }
 
         return shortUrlRepository.findById(id)
                 .map(ShortUrl::getLongUrl)
-                .orElseThrow(this::shortUrlNotFoundException);
-    }
-
-    private ResponseStatusException shortUrlNotFoundException() {
-        return new ResponseStatusException(
-                HttpStatus.NOT_FOUND,
-                "단축 URL을 찾을 수 없습니다."
-        );
+                .orElseThrow(ShortUrlNotFoundException::new);
     }
 
     private void validateUrl(String longUrl) {

src/main/resources/application.yml

@@ -13,6 +13,7 @@ spring:
     url: ${DB_URL:jdbc:mysql://localhost:3306/url_shortener?serverTimezone=Asia/Seoul&characterEncoding=UTF-8}
     username: ${DB_USERNAME:url_shortener}
     password: ${DB_PASSWORD}
+
   jpa:
     hibernate:
       ddl-auto: update
@@ -21,6 +22,13 @@ spring:
       hibernate:
         format_sql: true
 
+  data:
+    redis:
+      host: ${REDIS_HOST:localhost}
+      port: ${REDIS_PORT:6379}
+      connect-timeout: 2s
+      timeout: 2s
+
 management:
   endpoints:
     web:

src/test/java/com/backendsystemdesignlab/urlshortener/controller/RedirectControllerTest.java

@@ -1,5 +1,6 @@
 package com.backendsystemdesignlab.urlshortener.controller;
 
+import com.backendsystemdesignlab.urlshortener.service.RedirectService;
 import com.backendsystemdesignlab.urlshortener.service.ShortUrlService;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
@@ -24,10 +25,13 @@ class RedirectControllerTest {
     @MockitoBean
     private ShortUrlService shortUrlService;
 
+    @MockitoBean
+    private RedirectService redirectService;
+
     @Test
     @DisplayName("단축 URL 요청 시 원본 URL로 302 리다이렉트한다")
     void redirect() throws Exception {
-        given(shortUrlService.getLongUrl("2TX"))
+        given(redirectService.findLongUrl("2TX"))
                 .willReturn("https://www.google.com");
 
         mockMvc.perform(get("/api/v1/2TX"))
@@ -41,7 +45,7 @@ void redirect() throws Exception {
     @Test
     @DisplayName("존재하지 않는 단축 URL은 404를 반환한다")
     void redirectNotFound() throws Exception {
-        given(shortUrlService.getLongUrl("missing"))
+        given(redirectService.findLongUrl("missing"))
                 .willThrow(new ResponseStatusException(
                         HttpStatus.NOT_FOUND,
                         "단축 URL을 찾을 수 없습니다."

src/test/java/com/backendsystemdesignlab/urlshortener/service/RedirectServiceTest.java

@@ -0,0 +1,99 @@
+package com.backendsystemdesignlab.urlshortener.service;
+
+import com.backendsystemdesignlab.urlshortener.cache.ShortUrlCache;
+import com.backendsystemdesignlab.urlshortener.encoding.Base62Encoder;
+import com.backendsystemdesignlab.urlshortener.exception.ShortUrlNotFoundException;
+import com.backendsystemdesignlab.urlshortener.url.domain.ShortUrl;
+import com.backendsystemdesignlab.urlshortener.url.repository.ShortUrlRepository;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.util.Optional;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.BDDMockito.then;
+
+@ExtendWith(MockitoExtension.class)
+class RedirectServiceTest {
+
+    @InjectMocks
+    private RedirectService redirectService;
+
+    @Mock
+    private ShortUrlCache shortUrlCache;
+    @Mock
+    private ShortUrlRepository shortUrlRepository;
+    @Mock
+    private Base62Encoder base62Encoder;
+
+    @Test
+    void 캐시에_URL이_있으면_DB를_조회하지_않는다() {
+        String shortCode = "2TX";
+        String longUrl = "https://www.google.com";
+
+        given(shortUrlCache.find(shortCode))
+                .willReturn(Optional.of(longUrl));
+
+        String result = redirectService.findLongUrl(shortCode);
+
+        assertThat(result).isEqualTo(longUrl);
+
+        then(shortUrlCache).should().find(shortCode);
+        then(base62Encoder).shouldHaveNoInteractions();
+        then(shortUrlRepository).shouldHaveNoInteractions();
+    }
+
+    @Test
+    void 캐시에_URL이_없으면_DB를_조회하고_캐시에_저장한다() {
+        String shortCode = "2TX";
+        String longUrl = "https://www.google.com";
+        long id = 12345L;
+
+        ShortUrl shortUrl = ShortUrl.create(longUrl);
+
+        given(shortUrlCache.find(shortCode))
+                .willReturn(Optional.empty());
+
+        given(base62Encoder.decode(shortCode))
+                .willReturn(id);
+
+        given(shortUrlRepository.findById(id))
+                .willReturn(Optional.of(shortUrl));
+
+        String result = redirectService.findLongUrl(shortCode);
+
+        assertThat(result).isEqualTo(longUrl);
+
+        then(shortUrlCache).should().find(shortCode);
+        then(base62Encoder).should().decode(shortCode);
+        then(shortUrlRepository).should().findById(id);
+        then(shortUrlCache).should().save(shortCode, longUrl);
+    }
+
+    @Test
+    void 캐시와_DB에_URL이_없으면_예외가_발생한다() {
+        String shortCode = "2TX";
+        long id = 12345L;
+
+        given(shortUrlCache.find(shortCode))
+                .willReturn(Optional.empty());
+
+        given(base62Encoder.decode(shortCode))
+                .willReturn(id);
+
+        given(shortUrlRepository.findById(id))
+                .willReturn(Optional.empty());
+
+        assertThatThrownBy(() -> redirectService.findLongUrl(shortCode))
+                .isInstanceOf(ShortUrlNotFoundException.class);
+
+        then(shortUrlCache).should().find(shortCode);
+        then(shortUrlRepository).should().findById(id);
+        then(shortUrlCache).shouldHaveNoMoreInteractions();
+    }
+}