version 5.4.2

Only wipe real (non-RTT) plugin data on an actual client reboot (boot
flag), not on every ordinary OVERDUE/DOWN -> UP recovery. A transient
network blip no longer erases CPU/memory/etc. history.

Also split the shared time-series chart into separate line/area segments
wherever the gap between samples is much larger than the typical spacing,
so missing data (host overdue, or history that simply hasn't accumulated
across a drop) renders as a visual gap instead of an interpolated line.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DEimzMv4Q5EjFg3hoiZ69T

.gitignore

@@ -16,3 +16,4 @@ uv.lock
 .superpowers/
 rndc-key
 docs/superpowers/
+graphify-out/

CHANGELOG.md

@@ -2,6 +2,31 @@
 
 All notable changes to this project are documented here, organized by release.
 
+## [5.4.2]
+
+### Fixed
+- preserve chart history across reconnects, show gaps for missing data
+
+---
+
+## [5.4.1]
+
+### Added
+- live-refresh Connectivity section and RTT charts every 30s
+- render RTT history chart per connection in Connectivity section
+- record RTT history per heartbeat for charting
+
+### Fixed
+- correct empty-state copy on Host Overview page
+- stop synthetic rtt_* keys from masking real plugin-data checks
+- use the latest RTT sample, not the oldest, in host info API
+- hide synthetic rtt history keys from plugin accordion list
+- remove extra blank line to pass flake8 E303 check
+- clear flap state when a host is dropped
+- correct plugin import path in docs, wire up orphaned footer template
+
+---
+
 ## [5.4.0]
 
 ### Added

CLAUDE.md

@@ -1,8 +1,97 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Working principles
+
 1. Don't assume. Don't hide confusion. Surface tradeoffs.
 2. Minimum code that solves the problem. Nothing speculative.
 3. Touch only what you must. Clean up only your own mess.
 4. Define success criteria. Loop until verified.
 
-This project's hbd daemon is deployed and in production on host w02 
+## Commands
-under user 'nagios', which you can reach via ssh nagios@w02.
+
- The hbc client is used on 30 hosts in multiple networks.
+```bash
+# Run tests
+pytest -q                        # all tests
+pytest tests/test_threshold.py   # single file
+pytest -k test_name              # single test
+
+# Lint and type check
+tox -e lint     # flake8 over hbd/ and tests/
+tox -e mypy     # mypy over hbd/
+
+# Install for development
+pip install -e ".[all,dev]"
+
+# Run server
+python -m hbd.server.cli serve -c .hb.yaml -f -v
+
+# Generate a password hash
+hbd passwd <username>
+```
+
+Tests live in `tests/` (pytest, imported as a package). A second directory `test/` contains only TLS fixtures (`.pem` files), not test code.
+
+Line length: 111 characters (`black`, `flake8`, both configured).
+
+## Architecture
+
+The system has two components: `hbc` (client) and `hbd` (server), both in the `hbd` Python package.
+
+```
+hbd/
+  common/    # proto.py (encode/decode), utils.py
+  client/    # hbc: plugins/, main.py, config.py, plugin.py
+  server/    # hbd: all server modules
+```
+
+### Server module map
+
+| Module | Role |
+|---|---|
+| `cli.py` | Argument parsing, entry point, daemon startup |
+| `main.py` | Asyncio runtime: starts UDP, HTTP, WebSocket; pickle save/load |
+| `hbdclass.py` | `Host` and `Connection` domain objects; DNS queue |
+| `udp.py` | UDP datagram listener; processes `HTB` and `PLG` messages; sets/resets overdue timers |
+| `http.py` | aiohttp web server; all REST API routes (`/api/0/`) and page routes |
+| `ws.py` | WebSocket broadcast to connected dashboard clients |
+| `notify.py` | Notification dispatch (Pushover, email, Mattermost, Matrix, Signal, SMS); `eventlog()` is the single choke-point for all alert events |
+| `threshold.py` | Threshold evaluation against plugin metrics; state transitions (OK/WARNING/CRITICAL/UNKNOWN) |
+| `monitor.py` | Timer cleanup on shutdown (reachability is event-driven via timers in `udp.py`, not polled) |
+| `data.py` | Shared in-memory message ring buffer |
+| `journal.py` | JSONL message journal with size-based rotation |
+| `users.py` | Session management, password hashing (PBKDF2), role checks |
+| `config.py` | Config loading and defaults |
+| `configio.py` | Config file read/write via `ruamel.yaml` (preserves comments) |
+| `settings.py` | Settings sections for the web UI settings page |
+| `dns.py` | `nsupdate` integration for dynamic DNS |
+| `oauth.py` | OAuth2 login (Gitea) |
+
+### Key data flows
+
+**Heartbeat received:** `udp.py` decodes the `HTB` datagram → updates `Connection` state in `hbdclass.py` → resets overdue asyncio timer → broadcasts via `ws.py` → `notify.py` fires connectivity alerts on state change.
+
+**Plugin data received:** `udp.py` decodes `PLG` datagram → stores on `Host` → `threshold.py` evaluates against configured thresholds → `notify.py` fires threshold alerts on state transitions.
+
+**State persistence:** `Host.hosts` dict + `data.msgs` ring + active sessions are pickled every 5 minutes and on clean shutdown. Asyncio timers are stripped before pickling (`Connection.__getstate__`).
+
+**Config reload:** SIGHUP → `configio.py` re-reads YAML → live-updates hosts, thresholds, users, notification channels. Port/cert/pickle/journal changes require a full restart.
+
+### Client plugin system
+
+Plugins in `hbd/client/plugins/` subclass `InfoPlugin` (collected once, on demand) or `MonitorPlugin` (periodic). `initialize()` returns `False` to self-disable. Data is sent as `PLG` UDP messages.
+
+`hbc_mini.py` (scripts/) and `hbc_mini.c` (scripts/c/) are standalone single-file clients with no external dependencies.
+
+### Protocol
+
+All UDP messages: `!<ID>: <zlib-compressed key=value payload>`. Encoding in `hbd/common/proto.py`. Lists/dicts encoded as JSON with `@` prefix; booleans as `1`/`0`.
+
+### Web UI
+
+Jinja2 templates in `hbd/server/templates/`. Static assets in `hbd/server/static/`. Live pages (`/live`, `/plugins`) use WebSocket connections for real-time push.
+
+### CI
+
+Gitea Actions workflow at `.gitea/workflows/release.yml`.

README.md

@@ -20,7 +20,7 @@ A lightweight UDP-based host monitoring system. Monitored hosts run a client (`h
   └────────────────────┘              └────────────────────────────┘
 ```
 
-**Package:** `hbd` v5.4.0
+**Package:** `hbd` v5.4.2
 **Python:** 3.11+
 
 ### Subpackages

docs/PLUGIN_DEVELOPMENT.md

@@ -21,7 +21,7 @@ Heartbeat's plugin system is designed to be simple yet powerful. Plugins are Pyt
 ### Key Concepts
 
 - **Plugin Registry**: Central registry that manages all loaded plugins
-- **Plugin Loader**: Automatically discovers and loads plugins from the `hbd/plugins/` directory
+- **Plugin Loader**: Automatically discovers and loads plugins from the `hbd/client/plugins/` directory
 - **Plugin Types**: InfoPlugin (static data) and MonitorPlugin (periodic metrics)
 - **Async/Await**: All plugin methods are async for non-blocking operation
 
@@ -64,7 +64,7 @@ Decide whether your plugin collects static information (InfoPlugin) or dynamic m
 
 ### Step 2: Create Plugin File
 
-Create a new Python file in `hbd/plugins/` directory:
+Create a new Python file in `hbd/client/plugins/` directory:
 
 ```python
 """
@@ -82,7 +82,7 @@ try:
 except ImportError:
     psutil = None
 
-from hbd.plugin import MonitorPlugin  # or InfoPlugin
+from hbd.client.plugin import MonitorPlugin  # or InfoPlugin
 
 logger = logging.getLogger(__name__)
 
@@ -193,7 +193,7 @@ from pathlib import Path
 # Add parent directory to path
 sys.path.insert(0, str(Path(__file__).parent))
 
-from hbd.plugins.my_awesome_plugin import MyAwesomePlugin
+from hbd.client.plugins.my_awesome_plugin import MyAwesomePlugin
 
 async def test():
     # Create plugin instance
@@ -224,7 +224,7 @@ Understanding the plugin lifecycle helps you implement plugins correctly:
 
 ```
 1. Plugin Discovery
-   └─> Loader scans hbd/plugins/ directory
+   └─> Loader scans hbd/client/plugins/ directory
    └─> Finds Python files (except those starting with _)
    └─> Imports modules
 
@@ -378,7 +378,7 @@ Document your plugin thoroughly:
 ### Example 1: Simple InfoPlugin
 
 ```python
-from hbd.plugin import InfoPlugin
+from hbd.client.plugin import InfoPlugin
 import platform
 
 class SimpleInfoPlugin(InfoPlugin):
@@ -406,7 +406,7 @@ plugin = SimpleInfoPlugin
 ### Example 2: MonitorPlugin with State
 
 ```python
-from hbd.plugin import MonitorPlugin
+from hbd.client.plugin import MonitorPlugin
 import time
 
 class CounterPlugin(MonitorPlugin):
@@ -442,7 +442,7 @@ plugin = CounterPlugin
 ### Example 3: Plugin with External Command
 
 ```python
-from hbd.plugin import MonitorPlugin
+from hbd.client.plugin import MonitorPlugin
 import asyncio
 
 class CommandPlugin(MonitorPlugin):
@@ -561,7 +561,7 @@ python -m hbd.hbc -c test_config.yaml --verbose
 
 ## Further Reading
 
-- [Plugin Framework Source](../hbd/plugin.py) - Core plugin implementation
+- [Plugin Framework Source](../hbd/client/plugin.py) - Core plugin implementation
-- [Built-in Plugins](../hbd/plugins/) - Examples of working plugins
+- [Built-in Plugins](../hbd/client/plugins/) - Examples of working plugins
 - [Nagios Integration](NAGIOS_INTEGRATION.md) - Running external plugins
 - [Configuration Guide](../hbd/config_example.yaml) - Full configuration reference

hbd/__init__.py

@@ -14,4 +14,4 @@ Install options:
 """
 
 __all__ = ["__version__"]
-__version__ = "5.4.0"
+__version__ = "5.4.2"

hbd/server/flap.py

@@ -100,6 +100,17 @@ def observe(host: str, service: str, level: str) -> str:
     return SUPPRESS
 
 
+def clear_host(host: str) -> None:
+    """Discard all flap state for *host* (called when a host is dropped).
+
+    A dropped host may be mid-flap with no RECOVER ever received, in which
+    case ``ok_since`` stays ``None`` and ``_sweep`` can never clear it on its
+    own — the state would otherwise persist forever.
+    """
+    for key in [k for k in _state if k[0] == host]:
+        del _state[key]
+
+
 def flapping_services(host: str) -> list:
     """Return the services of *host* that are currently flapping.
 

hbd/server/http.py

@@ -14,6 +14,7 @@ import logging
 from aiohttp import web
 import jinja2
 from . import data
+from . import flap as flap_mod
 from . import notify as notify_mod
 from . import settings as settings_mod
 from . import users as users_mod
@@ -209,6 +210,16 @@ def _mask_config_for_api(config) -> dict:
     return result
 
 
+def _visible_plugin_names(plugin_data: dict) -> list:
+    """Plugin names to render as accordion sections.
+
+    Excludes synthetic rtt_ipv4 / rtt_ipv6 history streams (written by
+    udp.py for charting) which aren't real client plugins and have no
+    accordion renderer.
+    """
+    return [p for p in plugin_data.keys() if not p.startswith("rtt_")]
+
+
 def _build_host_info(host, threshold_checker=None) -> dict:
     """Assemble the info payload for GET /api/0/hosts/{hostname}/info."""
     hbc_version = None
@@ -264,7 +275,7 @@ def _build_host_info(host, threshold_checker=None) -> dict:
             "family": getattr(conn, "afam", family),
             "addr": getattr(conn, "addr", ""),
             "state": getattr(conn, "state", ""),
-            "rtt": (getattr(conn, "rtts", None) or [None])[0],
+            "rtt": (getattr(conn, "rtts", None) or [None])[-1],
             "statetime": getattr(conn, "statetime", None),
             "lastbeat": getattr(conn, "lastbeat", None),
         }
@@ -439,6 +450,7 @@ async def start(
             return web.json_response({"error": "Forbidden"}, status=403)
         eventlog(uname, "INFO", "dropped")
         del hbdclass.Host.hosts[uname]
+        flap_mod.clear_host(uname)
         return web.Response(text="Done")
 
     async def register(request):
@@ -765,7 +777,7 @@ async def start(
             if host.plugin_data:
                 hosts_with_plugins.append({
                     "name": hostname,
-                    "plugins": list(host.plugin_data.keys()),
+                    "plugins": _visible_plugin_names(host.plugin_data),
                     "is_owner": _can_own_host(current_user, host),
                     "owner": host.owner,
                 })

hbd/server/templates/about.html

@@ -107,6 +107,8 @@
       </section>
     </div>
 
+    {% include 'foot.html' %}
+
     <script>
       (function() {
         var startEpoch = {{ start_epoch }};

hbd/server/templates/menu.html

@@ -1,2 +0,0 @@
-<!-- <label for="drawer-toggle" id="drawer-toggle-label"></label>
-s<header>{{ header }}</header> -->

hbd/server/templates/plugins.html

@@ -290,8 +290,8 @@
 
       {% if not hosts %}
       <div class="no-data">
-        <p>No hosts with plugin data available</p>
+        <p>No hosts have connected yet</p>
-        <p style="font-size:0.9em;margin-top:10px;">Hosts will appear here once they start sending plugin metrics</p>
+        <p style="font-size:0.9em;margin-top:10px;">Hosts will appear here once they start sending heartbeats</p>
       </div>
       {% else %}
       <div id="hosts-container">
@@ -445,8 +445,12 @@
         </div>`;
 
         if (data.connections && data.connections.length) {
-          html += `<div class="info-thresholds-title">Connectivity</div>
+          html += `<div class="info-thresholds-title">Connectivity</div>`;
-            <table class="data-table"><thead><tr>
+          for (const c of data.connections) {
+            html += `<div class="info-note">${escHtml(c.family)} &middot; ${escHtml(c.addr || '—')} RTT</div>
+              <div id="rtt-chart-${hostname}-${escHtml(c.family)}" style="margin-bottom:8px;"></div>`;
+          }
+          html += `<table class="data-table"><thead><tr>
               <th>Family</th><th>Address</th><th>State</th>
               <th class="num">RTT</th><th>Last Change</th><th>Last Packet</th>
             </tr></thead><tbody>`;
@@ -495,6 +499,15 @@
         }
 
         el.innerHTML = html;
+
+        if (data.connections && data.connections.length) {
+          const rttThresholds = (data.thresholds || []).find(t => t.metric === 'rtt') || null;
+          for (const c of data.connections) {
+            fetchRttHistory(hostname, c.family)
+              .then(samples => renderRttChart(hostname, c.family, samples, rttThresholds))
+              .catch(() => {});
+          }
+        }
       }
 
       async function fetchHostGlance(hostname) {
@@ -809,15 +822,11 @@
         return json.samples || [];
       }
 
-      function renderCpuChart(hostname, samples) {
+      function renderTimeSeriesChart(elId, pts, opts) {
-        const el = document.getElementById(`cpu-chart-${hostname}`);
+        const el = document.getElementById(elId);
-        if (!el || !samples.length) return;
+        if (!el || pts.length < 2) { if (el) el.style.display = 'none'; return; }
-
-        const pts = samples
-          .filter(s => s.data.cpu_percent != null)
-          .map(s => ({ t: s.timestamp, v: s.data.cpu_percent }));
-        if (pts.length < 2) { el.style.display = 'none'; return; }
 
+        const unitSuffix = opts.unitSuffix || '';
         const W = 600, H = 80, PAD = { top: 6, right: 8, bottom: 18, left: 28 };
         const cW = W - PAD.left - PAD.right;
         const cH = H - PAD.top - PAD.bottom;
@@ -826,26 +835,49 @@
         const tRange = tMax - tMin || 1;
         const x = t => PAD.left + ((t - tMin) / tRange) * cW;
 
-        // Auto-scale Y axis with 10% padding, clamped to [0, 100]
+        // Auto-scale Y axis with 10% padding, optionally clamped to opts.yDomain
         const vMin = Math.min(...pts.map(p => p.v));
         const vMax = Math.max(...pts.map(p => p.v));
         const vRange = vMax - vMin || 1;
         const vPad = Math.max(vRange * 0.1, 1);
-        const yLow  = Math.max(0,   vMin - vPad);
+        const domainLow  = Array.isArray(opts.yDomain) ? opts.yDomain[0] : 0;
-        const yHigh = Math.min(100, vMax + vPad);
+        const domainHigh = Array.isArray(opts.yDomain) ? opts.yDomain[1] : Infinity;
+        const yLow  = Math.max(domainLow,  vMin - vPad);
+        const yHigh = Math.min(domainHigh, vMax + vPad);
         const yRange = yHigh - yLow || 1;
         const y = v => PAD.top + cH - ((v - yLow) / yRange) * cH;
 
-        // Build polyline points and filled area path
+        // Color based on latest value
-        const linePoints = pts.map(p => `${x(p.t).toFixed(1)},${y(p.v).toFixed(1)}`).join(' ');
-        const areaPath = `M${x(pts[0].t).toFixed(1)},${(PAD.top + cH).toFixed(1)} ` +
-          pts.map(p => `L${x(p.t).toFixed(1)},${y(p.v).toFixed(1)}`).join(' ') +
-          ` L${x(pts[pts.length-1].t).toFixed(1)},${(PAD.top + cH).toFixed(1)} Z`;
-
-        // Color based on latest absolute CPU %
         const latest = pts[pts.length - 1].v;
-        const strokeColor = latest > 90 ? '#e53935' : latest > 70 ? '#fb8c00' : '#43a047';
+        const { stroke: strokeColor, fill: fillColor } = opts.colorFor(latest);
-        const fillColor   = latest > 90 ? '#ffcdd2' : latest > 70 ? '#ffe0b2' : '#c8e6c9';
+
+        // Split into segments wherever the gap between consecutive samples is
+        // much larger than the typical spacing (e.g. the host was overdue/down
+        // for a while) — draw each segment separately so missing data reads as
+        // a visual gap instead of an interpolated line across dead time.
+        const deltas = [];
+        for (let i = 1; i < pts.length; i++) deltas.push(pts[i].t - pts[i - 1].t);
+        deltas.sort((a, b) => a - b);
+        const medianDelta = deltas[Math.floor(deltas.length / 2)];
+        const gapThreshold = medianDelta * 2.5;
+
+        const segments = [[pts[0]]];
+        for (let i = 1; i < pts.length; i++) {
+          if (pts[i].t - pts[i - 1].t > gapThreshold) segments.push([]);
+          segments[segments.length - 1].push(pts[i]);
+        }
+
+        let linePolylines = '';
+        let areaPaths = '';
+        for (const seg of segments) {
+          if (seg.length < 2) continue;
+          const segPoints = seg.map(p => `${x(p.t).toFixed(1)},${y(p.v).toFixed(1)}`).join(' ');
+          linePolylines += `<polyline points="${segPoints}" fill="none" stroke="${strokeColor}" stroke-width="1.5" stroke-linejoin="round"/>`;
+          const segArea = `M${x(seg[0].t).toFixed(1)},${(PAD.top + cH).toFixed(1)} ` +
+            seg.map(p => `L${x(p.t).toFixed(1)},${y(p.v).toFixed(1)}`).join(' ') +
+            ` L${x(seg[seg.length-1].t).toFixed(1)},${(PAD.top + cH).toFixed(1)} Z`;
+          areaPaths += `<path d="${segArea}" fill="${fillColor}" opacity="0.6"/>`;
+        }
 
         // Compute nice tick step for ~3-5 grid lines
         const rawStep = yRange / 4;
@@ -855,7 +887,7 @@
         let gridLines = '';
         for (let v = tickStart; v <= yHigh + 0.001; v += niceStep) {
           const yy = y(v).toFixed(1);
-          const label = Number.isInteger(v) ? v : v.toFixed(1);
+          const label = (Number.isInteger(v) ? v : v.toFixed(1)) + unitSuffix;
           gridLines += `<line x1="${PAD.left}" y1="${yy}" x2="${PAD.left + cW}" y2="${yy}" stroke="#e0e0e0" stroke-width="1"/>`;
           gridLines += `<text x="${(PAD.left - 3).toFixed(1)}" y="${yy}" text-anchor="end" dominant-baseline="middle" font-size="8" fill="#999">${label}</text>`;
         }
@@ -872,21 +904,65 @@
         el.innerHTML = `<svg viewBox="0 0 ${W} ${H}" preserveAspectRatio="none"
           style="width:100%;height:${H}px;display:block;">
           <defs>
-            <clipPath id="cpu-clip-${hostname}">
+            <clipPath id="${opts.clipId}">
               <rect x="${PAD.left}" y="${PAD.top}" width="${cW}" height="${cH}"/>
             </clipPath>
           </defs>
           ${gridLines}
           <line x1="${PAD.left}" y1="${PAD.top}" x2="${PAD.left}" y2="${PAD.top + cH}" stroke="#ccc" stroke-width="1"/>
           <line x1="${PAD.left}" y1="${PAD.top + cH}" x2="${PAD.left + cW}" y2="${PAD.top + cH}" stroke="#ccc" stroke-width="1"/>
-          <g clip-path="url(#cpu-clip-${hostname})">
+          <g clip-path="url(#${opts.clipId})">
-            <path d="${areaPath}" fill="${fillColor}" opacity="0.6"/>
+            ${areaPaths}
-            <polyline points="${linePoints}" fill="none" stroke="${strokeColor}" stroke-width="1.5" stroke-linejoin="round"/>
+            ${linePolylines}
           </g>
           ${xLabels}
         </svg>`;
       }
 
+      function renderCpuChart(hostname, samples) {
+        const pts = samples
+          .filter(s => s.data.cpu_percent != null)
+          .map(s => ({ t: s.timestamp, v: s.data.cpu_percent }));
+
+        renderTimeSeriesChart(`cpu-chart-${hostname}`, pts, {
+          yDomain: [0, 100],
+          clipId: `cpu-clip-${hostname}`,
+          colorFor: (latest) => ({
+            stroke: latest > 90 ? '#e53935' : latest > 70 ? '#fb8c00' : '#43a047',
+            fill:   latest > 90 ? '#ffcdd2' : latest > 70 ? '#ffe0b2' : '#c8e6c9',
+          }),
+        });
+      }
+
+      async function fetchRttHistory(hostname, family) {
+        const plugin = `rtt_${family.toLowerCase()}`;
+        const r = await fetch(`/api/0/hosts/${encodeURIComponent(hostname)}/plugins/${plugin}?limit=100`);
+        if (!r.ok) return [];
+        const json = await r.json();
+        return json.samples || [];
+      }
+
+      function renderRttChart(hostname, family, samples, rttThresholds) {
+        const pts = samples
+          .filter(s => s.data.rtt != null && s.data.rtt > 0)
+          .map(s => ({ t: s.timestamp, v: s.data.rtt }));
+
+        renderTimeSeriesChart(`rtt-chart-${hostname}-${family}`, pts, {
+          yDomain: 'auto',
+          clipId: `rtt-clip-${hostname}-${family}`,
+          unitSuffix: ' ms',
+          colorFor: (latest) => {
+            if (rttThresholds?.critical != null && latest > rttThresholds.critical) {
+              return { stroke: '#e53935', fill: '#ffcdd2' };
+            }
+            if (rttThresholds?.warning != null && latest > rttThresholds.warning) {
+              return { stroke: '#fb8c00', fill: '#ffe0b2' };
+            }
+            return { stroke: '#1976d2', fill: '#bbdefb' };
+          },
+        });
+      }
+
       function renderCpuTable(hostname, d) {
         const KEYS = [
           ['cpu_percent',      'CPU Usage',         'bar'],
@@ -1293,6 +1369,11 @@
         document.querySelectorAll('.host-card:not(.collapsed)').forEach(card => {
           const hostname = card.dataset.hostname;
 
+          fetchHostInfo(hostname).then(data => {
+            infoCache[hostname] = data;
+            renderInfoSection(hostname, data);
+          }).catch(() => {});
+
           card.querySelectorAll('.plugin-accordion:not(.collapsed)').forEach(acc => {
             const pname = acc.dataset.plugin;
             if (!GLANCE_PLUGINS.includes(pname)) {

hbd/server/udp.py

@@ -319,6 +319,16 @@ def restore_connection_timers(hbdclass, ctx):
     logger.info("Restored timers for %d connection(s)", restored)
 
 
+def _is_rtt_key(plugin_name: str) -> bool:
+    """True for synthetic RTT-history keys (rtt_ipv4/rtt_ipv6), not real plugin data."""
+    return plugin_name.startswith("rtt_")
+
+
+def _has_real_plugin_data(plugin_data: dict) -> bool:
+    """True if plugin_data holds any real (non-RTT) client-collected plugin data."""
+    return any(not _is_rtt_key(k) for k in plugin_data)
+
+
 def handle_datagram(msg: dict, addr, transport, ctx: dict):
     """Handle a parsed datagram message.
 
@@ -385,7 +395,7 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
         host.doesack = msg.get("acks", -1)
         # send ACK back; ask client to resend plugin info when we have none yet
         rmsg = {"time": time.time()}
-        if not host.plugin_data:
+        if not _has_real_plugin_data(host.plugin_data):
             rmsg["request_update"] = 1
         opkt = dicttos("ACK", rmsg)
         try:
@@ -511,12 +521,17 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
         # Transition to UP and log/notify if appropriate
         lasts = conn.state
         d = conn.newstate(hbdcls.Connection.UP, now)
+        if boot:
             # On reboot, pre-boot plugin data and derived alerts are stale.
             # Cancel all plugin timers and wipe plugin state so timers restart
-        # cleanly from the first two post-boot samples.
+            # cleanly from the first two post-boot samples. An ordinary
+            # reconnect (no boot flag) doesn't invalidate the client's
+            # already-collected data, so it's left alone — this keeps chart
+            # history intact across a transient network blip.
             for pname in list(host.plugin_timers):
                 host.cancel_plugin_timer(pname)
-        host.plugin_data.clear()
+            for pname in [k for k in host.plugin_data if not _is_rtt_key(k)]:
+                del host.plugin_data[pname]
         stale_plugin_keys = [
             k for k in host.alert_states
             if k not in ("rtt",) and not k.startswith("connectivity.")
@@ -562,6 +577,10 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
     if interval > 0:
         host.interval = interval
 
+    # Record RTT history for charting
+    if rtt is not None:
+        host.add_plugin_data(f"rtt_{conn.afam.lower()}", {"rtt": rtt}, timestamp=now)
+
     # Timer-based reachability monitoring
     # Reset overdue timer on every heartbeat
     if interval > 0 and conn.getstate() != hbdcls.Connection.DOWN:

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "hbd"
-version = "5.4.0"
+version = "5.4.2"
 description = "Heartbeat monitoring system — client (hbc) and server (hbd)"
 readme = "README.md"
 requires-python = ">=3.11"

scripts/hbc_mini.py

@@ -41,7 +41,7 @@ from pathlib import Path
 from typing import Any, Dict, List, Optional, Tuple
 
 # updated by scripts/bumpminor.sh
-__version__ = "5.4.0"
+__version__ = "5.4.2"
 
 # ---------------------------------------------------------------------------
 # Protocol  (mirrors hbd/common/proto.py)

tests/test_flap.py

@@ -98,6 +98,26 @@ def test_alert_during_the_quiet_window_keeps_it_flapping():
     assert flap.flapping_services("h1") == ["cpu"]
 
 
+# --- host removal ------------------------------------------------------------
+
+def test_clear_host_drops_flapping_state_even_without_a_recover():
+    # A host dropped mid-flap (no RECOVER ever received) must not stay
+    # flapping forever: nothing will ever set ok_since for it again.
+    alerts(4)
+    assert flap.flapping_services("h1") == ["cpu"]
+    flap.clear_host("h1")
+    assert flap.flapping_services("h1") == []
+    assert flap.observe("h1", "cpu", "CRITICAL") == flap.PASS
+
+
+def test_clear_host_only_affects_the_named_host():
+    alerts(4, host="h1")
+    alerts(4, host="h2")
+    flap.clear_host("h1")
+    assert flap.flapping_services("h1") == []
+    assert flap.flapping_services("h2") == ["cpu"]
+
+
 # --- keying -----------------------------------------------------------------
 
 def test_services_and_hosts_are_tracked_independently():

tests/test_http_host_info.py

@@ -1,5 +1,4 @@
 """Tests for _build_host_info helper in http.py."""
-import pytest
 from unittest.mock import MagicMock
 from hbd.server.http import _build_host_info
 
@@ -175,11 +174,11 @@ def test_build_host_info_covers_empty_when_exact_matches_only():
 
 
 class _FakeConnFull:
-    def __init__(self, afam, addr, state, rtt, statetime, lastbeat):
+    def __init__(self, afam, addr, state, rtt, statetime, lastbeat, rtts=None):
         self.afam = afam
         self.addr = addr
         self.state = state
-        self.rtts = [rtt]
+        self.rtts = rtts if rtts is not None else [rtt]
         self.statetime = statetime
         self.lastbeat = lastbeat
 
@@ -200,3 +199,14 @@ def test_build_host_info_connections_empty():
     host = _FakeHost()
     result = _build_host_info(host)
     assert result["connections"] == []
+
+
+def test_build_host_info_connection_rtt_uses_latest_sample():
+    """rtt should reflect the most recent sample, not the oldest retained one."""
+    host = _FakeHost(connections={
+        "IPv4": _FakeConnFull("IPv4", "10.0.0.5", "up", None, 1000.0, 2000.0,
+                              rtts=[100.0, 50.0, 14.2]),
+    })
+    result = _build_host_info(host)
+    conns = {c["family"]: c for c in result["connections"]}
+    assert conns["IPv4"]["rtt"] == 14.2

tests/test_http_plugins_page.py

@@ -0,0 +1,23 @@
+"""Tests for the plugin-accordion visibility filter in http.py."""
+from hbd.server.http import _visible_plugin_names
+
+
+def test_visible_plugin_names_excludes_rtt_history_keys():
+    plugin_data = {
+        "cpu_monitor": [],
+        "rtt_ipv4": [],
+        "rtt_ipv6": [],
+        "network_monitor": [],
+    }
+    result = _visible_plugin_names(plugin_data)
+    assert sorted(result) == ["cpu_monitor", "network_monitor"]
+
+
+def test_visible_plugin_names_empty_when_no_plugins():
+    assert _visible_plugin_names({}) == []
+
+
+def test_visible_plugin_names_keeps_names_not_prefixed_with_rtt_():
+    plugin_data = {"nagios_runner": [], "os_info": []}
+    result = _visible_plugin_names(plugin_data)
+    assert sorted(result) == ["nagios_runner", "os_info"]

tests/test_udp_rtt_history.py

@@ -0,0 +1,153 @@
+"""Tests for RTT history capture in udp.py's handle_datagram."""
+import time
+
+from hbd.common.proto import dicttos
+from hbd.server import hbdclass
+from hbd.server.udp import handle_datagram, parse_message
+
+
+class _FakeTransport:
+    def __init__(self):
+        self.sent = []
+
+    def sendto(self, data, addr):
+        self.sent.append((data, addr))
+
+
+def _htb(name, rtt=None, interval=0, boot=0):
+    d = {"name": name, "interval": interval, "id": 0}
+    if rtt is not None:
+        d["rtt"] = rtt
+    if boot:
+        d["boot"] = boot
+    return parse_message(dicttos("HTB", d))
+
+
+def _base_ctx():
+    return {
+        "config": {},
+        "hbdclass": hbdclass,
+        "msg_to_websockets": None,
+        "DEBUG": 0,
+        "verbose": False,
+    }
+
+
+def test_handle_datagram_records_rtt_history_for_new_connection():
+    hbdclass.Host.hosts.pop("rtt-hist-host", None)
+    handle_datagram(_htb("rtt-hist-host", rtt=42.5), ("127.0.0.1", 50000),
+                    _FakeTransport(), _base_ctx())
+
+    host = hbdclass.Host.hosts["rtt-hist-host"]
+    samples = host.plugin_data.get("rtt_ipv4")
+    assert samples is not None
+    assert len(samples) == 1
+    ts, data = samples[0]
+    assert data == {"rtt": 42.5}
+    assert isinstance(ts, float)
+
+
+def test_handle_datagram_appends_rtt_history_across_heartbeats():
+    hbdclass.Host.hosts.pop("rtt-hist-host2", None)
+    transport = _FakeTransport()
+    ctx = _base_ctx()
+    handle_datagram(_htb("rtt-hist-host2", rtt=10.0), ("127.0.0.1", 50000), transport, ctx)
+    handle_datagram(_htb("rtt-hist-host2", rtt=20.0), ("127.0.0.1", 50000), transport, ctx)
+
+    host = hbdclass.Host.hosts["rtt-hist-host2"]
+    samples = host.plugin_data["rtt_ipv4"]
+    assert [d["rtt"] for _, d in samples] == [10.0, 20.0]
+
+
+def test_handle_datagram_skips_rtt_history_when_rtt_missing():
+    hbdclass.Host.hosts.pop("rtt-hist-host3", None)
+    handle_datagram(_htb("rtt-hist-host3", rtt=None), ("127.0.0.1", 50000),
+                    _FakeTransport(), _base_ctx())
+
+    host = hbdclass.Host.hosts["rtt-hist-host3"]
+    assert "rtt_ipv4" not in host.plugin_data
+
+
+def test_request_update_fires_on_recovery_even_with_rtt_history():
+    """Regression for Finding 1: rtt_* keys must not permanently disable the
+    request_update gate. A connection recovering from a non-UP state must
+    still be asked to resend real plugin data, even though rtt_ipv4 already
+    holds samples from before the drop.
+    """
+    hbdclass.Host.hosts.pop("rtt-hist-host4", None)
+    transport = _FakeTransport()
+    ctx = _base_ctx()
+
+    # First heartbeat: brand-new host, no plugin data at all yet.
+    handle_datagram(_htb("rtt-hist-host4", rtt=15.0), ("127.0.0.1", 50000), transport, ctx)
+    host = hbdclass.Host.hosts["rtt-hist-host4"]
+    assert host.plugin_data.get("rtt_ipv4")  # rtt history now non-empty
+
+    # Simulate a recovery: connection was dropped (e.g. OVERDUE->UP after a
+    # missed heartbeat) and is about to come back UP on the next heartbeat.
+    conn = host.connections["IPv4"]
+    conn.state = hbdclass.Connection.DOWN
+
+    transport.sent.clear()
+    handle_datagram(_htb("rtt-hist-host4", rtt=16.0), ("127.0.0.1", 50000), transport, ctx)
+
+    ack_data, _ = transport.sent[0]
+    ack = parse_message(ack_data)
+    assert ack.get("request_update")
+
+
+def test_ordinary_recovery_preserves_real_plugin_data_and_rtt_history():
+    """An ordinary reconnect (no boot flag) — e.g. OVERDUE->UP after a
+    transient network blip — must NOT wipe already-collected real plugin
+    data (e.g. cpu_monitor, os_info) or rtt_* history. Only an actual
+    client reboot invalidates that data (see the boot-flag test below).
+    """
+    hbdclass.Host.hosts.pop("rtt-hist-host5", None)
+    transport = _FakeTransport()
+    ctx = _base_ctx()
+
+    for rtt in (10.0, 11.0, 12.0):
+        handle_datagram(_htb("rtt-hist-host5", rtt=rtt), ("127.0.0.1", 50000), transport, ctx)
+
+    host = hbdclass.Host.hosts["rtt-hist-host5"]
+    assert len(host.plugin_data["rtt_ipv4"]) == 3
+
+    # Simulate a drop, and pretend the client had previously sent real
+    # plugin data (collected before the connection went down).
+    conn = host.connections["IPv4"]
+    conn.state = hbdclass.Connection.DOWN
+    host.add_plugin_data("os_info", {"os": "linux"}, timestamp=time.time())
+    assert "os_info" in host.plugin_data
+
+    # Ordinary recovery heartbeat — no boot flag.
+    handle_datagram(_htb("rtt-hist-host5", rtt=13.0), ("127.0.0.1", 50000), transport, ctx)
+
+    assert "os_info" in host.plugin_data
+    assert len(host.plugin_data["rtt_ipv4"]) == 4
+
+
+def test_boot_recovery_clears_real_plugin_data_but_preserves_rtt_history():
+    """A recovery heartbeat carrying the boot flag (client process actually
+    restarted) must still wipe stale real plugin data, while rtt_* history
+    (still a valid measurement, unaffected by a client reboot) survives.
+    """
+    hbdclass.Host.hosts.pop("rtt-hist-host6", None)
+    transport = _FakeTransport()
+    ctx = _base_ctx()
+
+    for rtt in (10.0, 11.0, 12.0):
+        handle_datagram(_htb("rtt-hist-host6", rtt=rtt), ("127.0.0.1", 50000), transport, ctx)
+
+    host = hbdclass.Host.hosts["rtt-hist-host6"]
+    assert len(host.plugin_data["rtt_ipv4"]) == 3
+
+    conn = host.connections["IPv4"]
+    conn.state = hbdclass.Connection.DOWN
+    host.add_plugin_data("os_info", {"os": "linux"}, timestamp=time.time())
+    assert "os_info" in host.plugin_data
+
+    # Recovery heartbeat with boot=1 — client process actually restarted.
+    handle_datagram(_htb("rtt-hist-host6", rtt=13.0, boot=1), ("127.0.0.1", 50000), transport, ctx)
+
+    assert "os_info" not in host.plugin_data
+    assert len(host.plugin_data["rtt_ipv4"]) == 4