hbc/server: request InfoPlugin refresh when host has no plugin data; update docs

- Server sets request_update=1 in ACK when host.plugin_data is empty
- hbc: AsyncConnection.request_info_event; handle_ack sets it on request_update
- hbc: _info_plugin_refresh_loop clears InfoPlugin caches and resends on demand
- hbc_mini: same via _request_info event and _info_refresh_loop
- docs/USERS.md: document client-declared owner config key
- docs/PLUGIN_DEVELOPMENT.md: document server-initiated InfoPlugin refresh

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/PLUGIN_DEVELOPMENT.md

@@ -8,6 +8,7 @@ This guide explains how to create custom plugins for the Heartbeat monitoring sy
 - [Plugin Types](#plugin-types)
 - [Creating a Plugin](#creating-a-plugin)
 - [Plugin Lifecycle](#plugin-lifecycle)
+- [Server-initiated InfoPlugin refresh](#server-initiated-infoplugin-refresh)
 - [Configuration](#configuration)
 - [Best Practices](#best-practices)
 - [Examples](#examples)
@@ -250,6 +251,28 @@ Understanding the plugin lifecycle helps you implement plugins correctly:
    └─> Plugin releases resources, closes connections
 ```
 
+## Server-initiated InfoPlugin refresh
+
+When a heartbeat packet arrives from a host the server has no plugin data for (e.g. after a server restart), the server sets `request_update = 1` in the ACK reply. The client detects this flag and immediately re-runs all InfoPlugins — clearing their cached results first — then resends the data as PLG messages.
+
+This means InfoPlugin data will always reach the server as soon as possible without requiring a client restart. No action is needed from plugin authors: the framework handles cache invalidation and re-collection automatically.
+
+The lifecycle for this case looks like:
+
+```
+Server restarts, host reconnects
+   └─> hbd receives HTB with no existing plugin_data for host
+   └─> hbd sets request_update=1 in ACK
+
+Client receives ACK
+   └─> Detects request_update flag
+   └─> Clears _cache on every registered InfoPlugin
+   └─> Calls collect() on each InfoPlugin
+   └─> Sends fresh PLG messages to server
+```
+
+If you write an `InfoPlugin` with side effects in `_collect_info()` (opening connections, writing files, etc.), be aware it may be called more than once per client session when this mechanism triggers.
+
 ## Configuration
 
 ### Plugin-Specific Configuration

docs/USERS.md

@@ -46,6 +46,24 @@ default_owner: andreas            # owns hosts with no explicit owner
                                   # falls back to the first admin user if omitted
 ```
 
+### Client-declared host ownership
+
+A host can declare its own owner directly in the hbc or hbc_mini client configuration. This is useful for hosts that are not listed in the server config, or during initial setup before a server-side config entry has been created.
+
+**`~/.hbc.yaml`** (hbc):
+```yaml
+owner: andreas
+```
+
+**`~/.hbc.json`** (hbc_mini):
+```json
+{ "owner": "andreas" }
+```
+
+When set, the value is included in the `os_info` plugin data sent to the server. The server applies it as `host.owner` the first time `os_info` arrives, provided no owner has been configured server-side for that host. Server-configured ownership always takes precedence.
+
+---
+
 ### Assigning roles to hosts
 
 ```yaml

hbd/client/main.py

@@ -59,6 +59,7 @@ class AsyncConnection:
         self._dead = False
         self._ever_opened = False
         self._open_fail_count = 0   # consecutive failures before first success
+        self.request_info_event: asyncio.Event = asyncio.Event()
 
         self.logger = logging.getLogger(f"hbc.conn.{addr}")
 
@@ -138,6 +139,9 @@ class AsyncConnection:
         
         self.ackcount += 1
         self.logger.debug(f"ACK received, RTT: {rtt:.1f}ms")
+        if msg.get("request_update"):
+            self.logger.info("server requested plugin info refresh")
+            self.request_info_event.set()
 
 
 class HeartbeatProtocol(asyncio.DatagramProtocol):
@@ -338,6 +342,26 @@ async def heartbeat_sender(conn: AsyncConnection, interval: int):
             raise
 
 
+async def _info_plugin_refresh_loop(conn: AsyncConnection, info_plugins: List):
+    """Wait for server requests to re-send InfoPlugin data."""
+    logger = logging.getLogger("hbc.plugins")
+    while running:
+        await conn.request_info_event.wait()
+        if not running:
+            break
+        conn.request_info_event.clear()
+        logger.info("refreshing InfoPlugins on server request")
+        for plugin in info_plugins:
+            plugin._cache = None
+            try:
+                data = await plugin.collect()
+                if data:
+                    await conn.sendto({"plugin": plugin.name, **data}, "PLG")
+                    logger.info(f"Resent {plugin.name} data")
+            except Exception as e:
+                logger.error(f"Error re-collecting {plugin.name}: {e}", exc_info=True)
+
+
 async def plugin_collector(conn: AsyncConnection, registry: PluginRegistry):
     """Collect and send plugin data.
 
@@ -369,24 +393,21 @@ async def plugin_collector(conn: AsyncConnection, registry: PluginRegistry):
     for plugin in monitor_plugins:
         by_interval[plugin.interval].append(plugin)
 
-    # Create tasks for each interval
+    # Create tasks for each interval; always include the info-refresh watcher
-    tasks = []
+    tasks = [asyncio.create_task(_info_plugin_refresh_loop(conn, info_plugins))]
     for interval, plugins in by_interval.items():
-        task = asyncio.create_task(
+        tasks.append(asyncio.create_task(
             plugin_collector_interval(conn, plugins, interval)
-        )
+        ))
-        tasks.append(task)
 
-    # Wait for all tasks
+    try:
-    if tasks:
+        await asyncio.gather(*tasks, return_exceptions=True)
-        try:
+    except asyncio.CancelledError:
-            await asyncio.gather(*tasks, return_exceptions=True)
+        logger.debug("Plugin collector cancelled, cancelling sub-tasks")
-        except asyncio.CancelledError:
+        for task in tasks:
-            logger.debug("Plugin collector cancelled, cancelling sub-tasks")
+            if not task.done():
-            for task in tasks:
+                task.cancel()
-                if not task.done():
+        raise
-                    task.cancel()
-            raise
 
 
 async def plugin_collector_interval(

hbd/server/udp.py

@@ -350,8 +350,10 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
 
     if msg.get("ID") == "HTB":
         host.doesack = msg.get("acks", -1)
-        # send ACK back
+        # send ACK back; ask client to resend plugin info when we have none yet
         rmsg = {"time": time.time()}
+        if not host.plugin_data:
+            rmsg["request_update"] = 1
         opkt = dicttos("ACK", rmsg)
         try:
             transport.sendto(opkt, addr)

scripts/hbc_mini.py

@@ -791,7 +791,7 @@ class _HeartbeatProtocol(asyncio.DatagramProtocol):
             msg_id = msg.get("ID")
             now = time.time()
             if msg_id == "ACK":
-                self._conn._handle_ack(now)
+                self._conn._handle_ack(msg, now)
             elif msg_id == "CMD":
                 asyncio.create_task(_handle_command(self._conn, msg))
             elif msg_id == "UPD":
@@ -818,6 +818,7 @@ class AsyncConnection:
         self.rtts: List[float] = [0.0]
         self._transport: Optional[asyncio.DatagramTransport] = None
         self._dead = False
+        self._request_info: asyncio.Event = asyncio.Event()
         self._log = logging.getLogger(f"hbc.conn.{addr}")
 
     async def open(self) -> bool:
@@ -836,12 +837,14 @@ class AsyncConnection:
             self._transport.close()
             self._transport = None
 
-    def _handle_ack(self, now: float):
+    def _handle_ack(self, msg: Dict[str, Any], now: float):
         rtt = (now - self.lastsend) * 1000.0
         self.rtts.append(rtt)
         if len(self.rtts) > 10:
             self.rtts.pop(0)
         self.ackcount += 1
+        if msg.get("request_update"):
+            self._request_info.set()
 
     async def sendto(self, msg: Dict[str, Any], msg_id: str = "HTB"):
         if self._dead:
@@ -974,6 +977,19 @@ async def _run_monitor_group(conn: AsyncConnection, plugins: List[Plugin], inter
         await _sleep(interval)
 
 
+async def _info_refresh_loop(conn: AsyncConnection, info: List[Plugin]):
+    log = logging.getLogger("hbc.plugins")
+    while _running:
+        await conn._request_info.wait()
+        if not _running:
+            break
+        conn._request_info.clear()
+        log.info("refreshing InfoPlugins on server request")
+        for plugin in info:
+            plugin._cache = None
+        await _run_info_plugins(conn, info)
+
+
 async def _plugin_collector(conn: AsyncConnection, plugins: List[Plugin]):
     info = [p for p in plugins if isinstance(p, InfoPlugin)]
     monitor = [p for p in plugins if isinstance(p, MonitorPlugin)]
@@ -984,12 +1000,10 @@ async def _plugin_collector(conn: AsyncConnection, plugins: List[Plugin]):
     for p in monitor:
         by_interval[p.interval].append(p)
 
-    if by_interval:
+    tasks = [asyncio.create_task(_info_refresh_loop(conn, info))]
-        await asyncio.gather(
+    tasks += [asyncio.create_task(_run_monitor_group(conn, grp, iv))
-            *[asyncio.create_task(_run_monitor_group(conn, grp, iv))
+              for iv, grp in by_interval.items()]
-              for iv, grp in by_interval.items()],
+    await asyncio.gather(*tasks, return_exceptions=True)
-            return_exceptions=True,
-        )
 
 
 # ---------------------------------------------------------------------------