feat(syslog): 优化大日志通道并增加异常连续消费兜底

- 128 KiB 及以上日志默认进入大日志 Topic
- InfluxDB 原文及达梦大字段超过 256 KiB 时截断保存
- 截断内容追加 HB_XDR_TRUNCATED 标记
- InfluxDB 写入失败时继续执行规则解析和达梦写入
- 未知或系统性异常优先写入普通/大日志 DLT
- DLT 写入失败时记录特殊告警并提交 offset，避免阻塞后续消息
- DLT 失败等待时间默认限制为 1 秒
- 增加连续性放行、DLT 成功及失败监控指标
- 更新 Docker Compose、v3 升级文档及相关测试

haobang-security-dm/syslog-serve/src/test/java/com/haobang/wal/SyslogWalServiceTest.java

@@ -98,6 +98,58 @@ class SyslogWalServiceTest {
         assertEquals(null, attempt.getDurableStage());
     }
 
+    @Test
+    void oversizedMessageIsRejectedBeforeEnteringWal() {
+        AppProperties properties = properties(tempDirectory);
+        properties.setSyslogMessageMaxBytes(4L);
+        properties.setSyslogWalMaxPendingBytes(16L);
+        service = new SyslogWalService(properties, new ObjectMapper());
+        service.initialize();
+
+        SyslogWalService.AdmissionResult result = service.tryAppend(
+                event("20260811-too-large", "12345"));
+
+        assertEquals(SyslogWalService.AdmissionResult.OVERSIZED, result);
+        assertEquals(1L, service.getOversizedCount());
+        assertEquals(0, service.getQueueSize());
+        assertEquals(0L, service.getPendingAppendBytes());
+    }
+
+    @Test
+    void pendingByteBudgetBackpressuresEvenWhenRecordQueueHasCapacity() {
+        AppProperties properties = properties(tempDirectory);
+        properties.setSyslogMessageMaxBytes(5L);
+        properties.setSyslogWalMaxPendingBytes(5L);
+        properties.setSyslogWalFlushRecords(100);
+        properties.setSyslogWalFlushIntervalMs(10000L);
+        service = new SyslogWalService(properties, new ObjectMapper());
+        service.initialize();
+
+        assertEquals(SyslogWalService.AdmissionResult.ACCEPTED,
+                service.tryAppend(event("20260811-first", "12345")));
+        assertEquals(SyslogWalService.AdmissionResult.BACKPRESSURE,
+                service.tryAppend(event("20260811-second", "x")));
+        assertEquals(5L, service.getPendingAppendBytes());
+        assertEquals(1L, service.getBackpressureCount());
+    }
+
+    @Test
+    void disabledHardLimitLetsOneOverBudgetRecordMakeProgressExclusively() {
+        AppProperties properties = properties(tempDirectory);
+        properties.setSyslogMessageMaxBytes(0L);
+        properties.setSyslogWalMaxPendingBytes(4L);
+        properties.setSyslogWalFlushRecords(100);
+        properties.setSyslogWalFlushIntervalMs(10000L);
+        service = new SyslogWalService(properties, new ObjectMapper());
+        service.initialize();
+
+        assertEquals(SyslogWalService.AdmissionResult.ACCEPTED,
+                service.tryAppend(event("20260811-over-budget", "12345")));
+        assertEquals(SyslogWalService.AdmissionResult.BACKPRESSURE,
+                service.tryAppend(event("20260811-waits", "x")));
+        assertEquals(5L, service.getPendingAppendBytes());
+    }
+
     @Test
     void forceBeforeCursorAndPersistSchemaV2() throws Exception {
         service = new SyslogWalService(properties(tempDirectory), new ObjectMapper());