fix(log_client): update example_log_client template to use RpcClient

- Replace legacy MsgClient (low-level TCP frames) with RpcClient (high-level
  RPC) to match dbv2's RpcServer interface; the old MsgClient-based version
  was incompatible with the current RPC routing protocol
- Apply all hardening fixes from the service copies:
  - Outer try/except in _flush_loop to prevent any exception from killing
    the background thread
  - _safe_json() helper for unserializable extra fields (fallback to str/repr)
  - Timestamp generated at push() (enqueue time) instead of _send() time
  - Event-based flush() synchronization instead of unreliable sleep(0.6)
  - Queue maxsize=10000 with drop-oldest policy to prevent unbounded memory
  - put_nowait with Full handling ensures push() never blocks business threads
  - RpcClient construction wrapped in try/except
- Add explicit service_name parameter example for all 4 services in comments
- This is the template file referenced by db/README.md and copied by new
  services; keeping it in sync prevents propagating old bugs

db/example_log_client.py

@@ -1,13 +1,14 @@
 """
-统一日志客户端 SDK — 各服务复制即用。
+统一日志客户端 SDK — 各服务复制即用（模板）。
 
 设计要点：
-  - 通过 pymsg TCP 调用 dbv2 execute 路由，逐条 INSERT 到 Logs 表
+  - 通过 pymsg RpcClient（高层 RPC 封装）调用 dbv2 execute 路由，逐条 INSERT 到 Logs 表
   - 异步非阻塞：内存队列 + 后台线程批量推送，不拖慢业务
-  - fail-safe：db 服务不可用时静默丢弃，绝不影响业务
+  - fail-safe：db 服务不可用时静默丢弃，绝不影响业务；后台线程任何异常都不会崩溃
   - 缓冲批量：队列满 50 条或超时 2 秒时自动 flush
+  - 时间戳：日志入队时即记录 ts，反映事件真实发生时间
 
-复制到目标服务目录后，按需修改 service_name 即可：:
+复制到目标服务目录后，按需修改底部全局单例的 service_name 即可：
 
     from log_client import logs
 
@@ -27,22 +28,36 @@ import atexit
 from datetime import datetime, timezone
 
 _sys.path.insert(0, _os.path.join(_os.path.dirname(__file__), ".."))
-from pymsg import MsgClient  # noqa: E402
+from pymsg import RpcClient, RpcError  # noqa: E402
 
 # ── 配置 ──────────────────────────────────────────────────────────────
 
-_DBV2_ADDR = '127.0.0.1'
+_DBV2_ADDR = _os.environ.get('DB_HOST', '127.0.0.1')
-_DBV2_PORT = 8005
+_DBV2_PORT = int(_os.environ.get('DB_PORT', '8005'))
 
 _BATCH_SIZE = 50         # 队列满 50 条时 flush
 _FLUSH_INTERVAL = 2.0    # 超时 2 秒强制 flush
 _TIMEOUT = 5             # socket 超时（秒）
+_QUEUE_MAXSIZE = 10000   # 队列上限，防止后台线程异常时内存无限增长；满则丢弃最旧条目
+
+
+def _safe_json(obj):
+    """安全序列化 extra 字段，不可序列化对象转为 repr 字符串，保证不抛异常。"""
+    try:
+        return json.dumps(obj, ensure_ascii=False, default=str)
+    except Exception:
+        return repr(obj)
+
+
+def _now_iso():
+    """生成当前 UTC 时间 ISO 字符串（在入队时调用，保证时间戳准确）。"""
+    return datetime.now(timezone.utc).isoformat()
 
 
 class LogClient:
     """异步批量日志推送客户端。
 
-    通过 MsgClient（pymsg TCP 协议）逐条 INSERT 到 dbv2 的 Logs 表。
+    通过 RpcClient（pymsg 高层 RPC 封装）逐条 INSERT 到 dbv2 的 Logs 表。
     service_name 用于在 dbv2 连接中标识来源，各服务复制时自行修改。
     """
 
@@ -52,9 +67,10 @@ class LogClient:
         self._service_name = service_name
         self._batch_size = batch_size
         self._flush_interval = flush_interval
-        self._queue = queue.Queue()
+        self._queue = queue.Queue(maxsize=_QUEUE_MAXSIZE)
         self._stop = threading.Event()
         self._flush_signal = threading.Event()
+        self._flush_done = threading.Event()
         self._thread = threading.Thread(target=self._flush_loop,
                                         daemon=True, name='log-client')
         self._thread.start()
@@ -63,14 +79,30 @@ class LogClient:
     # ── 公开接口 ────────────────────────────────────────────────────────
 
     def push(self, service, level, message, trace_id=None, extra=None):
-        """推送一条日志（非阻塞，立即返回）。"""
+        """推送一条日志（非阻塞，立即返回）。
-        self._queue.put({
+
+        队列满时静默丢弃最旧条目再放入新条目，保证不阻塞业务线程、不导致 OOM。
+        """
+        entry = {
+            'ts': _now_iso(),  # 入队时即生成时间戳，反映真实事件时间
             'service': service,
             'level': level,
             'message': message,
             'trace_id': trace_id,
             'extra': extra,
-        })
+        }
+        try:
+            self._queue.put_nowait(entry)
+        except queue.Full:
+            # 队列满：丢弃最旧的一条，再放入新条目（drop-oldest 策略）
+            try:
+                self._queue.get_nowait()
+            except queue.Empty:
+                pass
+            try:
+                self._queue.put_nowait(entry)
+            except queue.Full:
+                pass  # 极端竞争下仍失败则静默丢弃
 
     def debug(self, service, message, **kw):
         self.push(service, 'DEBUG', message, **kw)
@@ -89,8 +121,15 @@ class LogClient:
 
     def flush(self):
         """手动 flush 队列中剩余的日志（含后台线程持有的局部 batch）。"""
+        self._flush_done.clear()
         self._flush_signal.set()  # 通知后台线程立即 flush 其局部 batch
-        time.sleep(0.6)  # 等待后台线程响应
+        # 等待后台线程完成 flush（最多等待 flush_interval + 2 秒余量）
+        self._flush_done.wait(timeout=self._flush_interval + 2.0)
+        # 主线程排空队列中剩余条目
+        self._drain_queue_to_db()
+
+    def _drain_queue_to_db(self):
+        """排空主线程可见的队列中剩余条目，直接发送到 db。"""
         batch = []
         while True:
             try:
@@ -102,73 +141,103 @@ class LogClient:
                 break
         if batch:
             self._send(batch)
-        self._flush_signal.clear()
 
     # ── 内部实现 ────────────────────────────────────────────────────────
 
     def _flush_loop(self):
-        """后台线程：积攒到 batch_size 或超时 flush_interval 时发送。"""
+        """后台线程：积攒到 batch_size 或超时 flush_interval 时发送。
+
+        外层捕获所有异常，保证后台线程在任何情况下（网络故障、序列化错误等）
+        都不会死亡，避免日志队列无限增长导致 OOM。
+        """
         batch = []
         last_flush = time.monotonic()
 
         while not self._stop.is_set():
-            timeout = self._flush_interval - (time.monotonic() - last_flush)
-            chk_timeout = max(0.0, min(timeout, 0.5))
             try:
-                item = self._queue.get(timeout=chk_timeout)
+                timeout = self._flush_interval - (time.monotonic() - last_flush)
-                batch.append(item)
+                chk_timeout = max(0.1, min(timeout, 0.5))
-                while len(batch) < self._batch_size:
+                try:
-                    try:
+                    item = self._queue.get(timeout=chk_timeout)
-                        batch.append(self._queue.get_nowait())
+                    batch.append(item)
-                    except queue.Empty:
+                    while len(batch) < self._batch_size:
-                        break
+                        try:
-            except queue.Empty:
+                            batch.append(self._queue.get_nowait())
-                pass
+                        except queue.Empty:
+                            break
+                except queue.Empty:
+                    pass
 
-            should_flush = (
+                should_flush = (
-                len(batch) >= self._batch_size or
+                    len(batch) >= self._batch_size or
-                self._flush_signal.is_set() or
+                    self._flush_signal.is_set() or
-                (batch and time.monotonic() - last_flush >= self._flush_interval)
+                    (batch and time.monotonic() - last_flush >= self._flush_interval)
-            )
+                )
-            if should_flush and batch:
+                if should_flush and batch:
-                self._send(batch)
+                    try:
-                batch = []
+                        self._send(batch)
-                last_flush = time.monotonic()
+                    except Exception as e:
+                        # _send 内部已有细粒度异常处理，此处是最终安全网
+                        print(f"[log_client] _send 异常（已捕获，线程继续运行）: {e}",
+                              file=_sys.stderr)
+                    batch = []
+                    last_flush = time.monotonic()
+                    if self._flush_signal.is_set():
+                        self._flush_signal.clear()
+                        self._flush_done.set()
+            except Exception as e:
+                # 最外层安全网：任何意外异常都不应杀死日志线程
+                print(f"[log_client] _flush_loop 异常（已捕获，线程继续运行）: {e}",
+                      file=_sys.stderr)
+                time.sleep(0.5)  # 防止异常风暴导致 CPU 满载
 
         # 退出前 flush 剩余
         if batch:
-            self._send(batch)
+            try:
+                self._send(batch)
+            except Exception as e:
+                print(f"[log_client] 退出时 flush 异常: {e}", file=_sys.stderr)
+        self._flush_done.set()
 
     def _send(self, batch):
-        """通过 pymsg 使用 execute 路由逐条 INSERT 到 dbv2 Logs 表。"""
+        """通过 pymsg RpcClient（execute 路由）批量发送到 dbv2 Logs 表。
-        now = datetime.now(timezone.utc).isoformat()
+
+        整个 batch 复用一个 TCP 连接；网络错误时放弃本批剩余条目（fail-safe），
+        不抛异常给调用方。
+        """
         try:
-            client = MsgClient(_DBV2_ADDR, _DBV2_PORT, self._service_name + "-log")
+            client = RpcClient(_DBV2_ADDR, _DBV2_PORT, self._service_name + "-log")
-            for entry in batch:
-                extra_val = entry.get("extra")
-                payload = {
-                    "_route": "execute",
-                    "action": "insert",
-                    "table": "Logs",
-                    "values": {
-                        "ts": now,
-                        "service": entry.get("service"),
-                        "level": entry.get("level"),
-                        "message": entry.get("message"),
-                        "trace_id": entry.get("trace_id"),
-                        "extra": json.dumps(extra_val, ensure_ascii=False)
-                        if extra_val is not None else None,
-                    },
-                }
-                resp = client.call(json.dumps(payload), timeout=_TIMEOUT)
-                resp_obj = json.loads(resp)
-                if not resp_obj.get("success"):
-                    import sys
-                    print(f"[log_client] INSERT 失败: {resp_obj.get('error')}",
-                          file=sys.stderr)
         except Exception as e:
-            import sys
+            print(f"[log_client] 创建 RpcClient 失败: {e}", file=_sys.stderr)
-            print(f"[log_client] 发送失败: {e}", file=sys.stderr)
+            return
+
+        for entry in batch:
+            extra_val = entry.get("extra")
+            try:
+                extra_json = _safe_json(extra_val) if extra_val is not None else None
+            except Exception:
+                extra_json = None
+            payload = {
+                "action": "insert",
+                "table": "Logs",
+                "values": {
+                    "ts": entry.get("ts", _now_iso()),
+                    "service": entry.get("service"),
+                    "level": entry.get("level"),
+                    "message": entry.get("message"),
+                    "trace_id": entry.get("trace_id"),
+                    "extra": extra_json,
+                },
+            }
+            try:
+                client.call("execute", payload, timeout=_TIMEOUT)
+            except RpcError as e:
+                # 业务错误（如表结构不符）：打印后继续下一条
+                print(f"[log_client] INSERT 失败: {e}", file=_sys.stderr)
+            except Exception as e:
+                # 网络错误：db 不可用，放弃本批剩余（fail-safe）
+                print(f"[log_client] 发送失败: {e}", file=_sys.stderr)
+                break
 
     def _shutdown(self):
         """进程退出时 flush 剩余日志。"""
@@ -180,5 +249,7 @@ class LogClient:
 #  各服务复制时，把 "example" 改为自己的服务名即可。
 #  例如 dnfs/log_client.py → logs = LogClient(service_name="dnfs")
 #  例如 smtp/log_client.py → logs = LogClient(service_name="smtp")
+#  例如 static/log_client.py → logs = LogClient(service_name="static")
+#  例如 confs/log_client.py → logs = LogClient(service_name="confs")
 
-logs = LogClient()
+logs = LogClient(service_name="example")