feat(ranking): 랭킹 조회 관측 로그를 추가한다

src/test/kotlin/kr/co/vividnext/sodalive/v2/ranking/application/CreatorRankingQueryServiceTest.kt

@@ -8,11 +8,16 @@ import kr.co.vividnext.sodalive.v2.ranking.port.out.CreatorRankingSnapshotRecord
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertFalse
 import org.junit.jupiter.api.Assertions.assertNull
+import org.junit.jupiter.api.Assertions.assertThrows
 import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.DisplayName
 import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import org.springframework.boot.test.system.CapturedOutput
+import org.springframework.boot.test.system.OutputCaptureExtension
 import java.time.LocalDateTime
 
+@ExtendWith(OutputCaptureExtension::class)
 class CreatorRankingQueryServiceTest {
     @Test
     @DisplayName("스냅샷 후보와 조회 item 내부 모델은 순위 변화와 신규 진입 값을 담을 수 있다")
@@ -177,6 +182,37 @@ class CreatorRankingQueryServiceTest {
         assertEquals("profile-1.png", result.items.single().profileImageUrl)
     }
 
+    @Test
+    @DisplayName("크리에이터 랭킹 조회 성공은 순위 변화 노출 여부와 반환 수를 로그로 남긴다")
+    fun shouldLogCreatorRankingQuerySuccessWithResultCounts(output: CapturedOutput) {
+        val snapshotPort = FakeCreatorRankingQuerySnapshotPort()
+        snapshotPort.latestSnapshots = listOf(snapshot(creatorId = 1L, finalScore = 100.0))
+        val service = service(snapshotPort = snapshotPort)
+
+        service.getCreatorRankings(viewerMemberId = null)
+
+        assertTrue(output.out.contains("event=creator_ranking_query_success"))
+        assertTrue(output.out.contains("showRankChange=false"))
+        assertTrue(output.out.contains("itemCount=1"))
+        assertTrue(output.out.contains("blockedCreatorCount=0"))
+    }
+
+    @Test
+    @DisplayName("크리에이터 랭킹 조회 실패는 에러를 로그로 남기고 예외를 전파한다")
+    fun shouldLogCreatorRankingQueryFailureWithError(output: CapturedOutput) {
+        val snapshotPort = FakeCreatorRankingQuerySnapshotPort()
+        snapshotPort.latestFailure = IllegalStateException("latest snapshots failed")
+        val service = service(snapshotPort = snapshotPort)
+
+        val exception = assertThrows(IllegalStateException::class.java) {
+            service.getCreatorRankings(viewerMemberId = 99L)
+        }
+
+        assertEquals("latest snapshots failed", exception.message)
+        assertTrue(output.out.contains("event=creator_ranking_query_failure"))
+        assertTrue(output.out.contains("error=latest snapshots failed"))
+    }
+
     private fun service(
         snapshotPort: CreatorRankingSnapshotPort = FakeCreatorRankingQuerySnapshotPort(),
         blockPort: CreatorRankingBlockPort = FakeCreatorRankingBlockPort()
@@ -219,13 +255,17 @@ class CreatorRankingQueryServiceTest {
 private class FakeCreatorRankingQuerySnapshotPort : CreatorRankingSnapshotPort {
     var latestSnapshots: List<CreatorRankingSnapshotRecord> = emptyList()
     var previousSnapshots: List<CreatorRankingSnapshotRecord> = emptyList()
+    var latestFailure: RuntimeException? = null
 
     override fun findSnapshotsByAggregationPeriod(
         aggregationStartAtUtc: LocalDateTime,
         aggregationEndAtUtc: LocalDateTime
     ): List<CreatorRankingSnapshotRecord> = emptyList()
 
-    override fun findLatestSnapshots(): List<CreatorRankingSnapshotRecord> = latestSnapshots
+    override fun findLatestSnapshots(): List<CreatorRankingSnapshotRecord> {
+        latestFailure?.let { throw it }
+        return latestSnapshots
+    }
 
     override fun findPreviousCompletedSnapshots(): List<CreatorRankingSnapshotRecord> = previousSnapshots