midi-bridge: add prometheus metrics on :9091/metrics

- midi_messages_total: all MIDI messages - midi_notes_on/off_total: note-on/off counts - midi_last_status/note/velocity: last message tokens - midi_last_time_unix: epoch of last message - Removed MIDI counters from prometheus-exporter (bridge owns them)
2026-06-24 02:25:31 -07:00
parent 163ad4145b
commit caef6f04c8
2 changed files with 114 additions and 33 deletions
@@ -3,19 +3,33 @@

 Sends parsed MIDI messages as Pd-style 'midi status data1 data2;' strings
 to UDP ports for Pd (8081) and LED matrix visualization (8082).
+
+Exposes Prometheus metrics on :9091/metrics.
 """
-import os, socket, time, select, pathlib
+import os, socket, time, select, pathlib, threading, http.server

 PD_HOST = os.environ.get("MIDI_BRIDGE_HOST", "127.0.0.1")
 PD_PORT = int(os.environ.get("MIDI_BRIDGE_PORT", "8081"))
 VIZ_PORT = int(os.environ.get("VIZ_PORT", "8082"))
+METRICS_PORT = int(os.environ.get("MIDI_METRICS_PORT", "9091"))
+
+# ── Metrics ──
+midi_notes_on = 0
+midi_notes_off = 0
+midi_messages_total = 0
+midi_errors = 0
+last_status = 0
+last_note = 0
+last_velocity = 0
+last_time = 0.0
+_metrics_lock = threading.Lock()
+

 def _find_midi_dev():
    """Auto-detect rawmidi device. Preference: gadget f_midi > env override > host mode."""
    dev = os.environ.get("MIDI_BRIDGE_DEV")
    if dev:
        return dev
-    # Look for gadget f_midi card first
    cards = pathlib.Path("/proc/asound").glob("card*")
    for card_dir in cards:
        cmi = card_dir / "id"
@@ -24,17 +38,18 @@ def _find_midi_dev():
            midi_dev = f"/dev/snd/midiC{card_num}D0"
            if os.path.exists(midi_dev):
                return midi_dev
-    # Fallback: any rawmidi device
    rawdevs = sorted(pathlib.Path("/dev/snd").glob("midiC?D0"))
    if rawdevs:
        return str(rawdevs[0])
-    return "/dev/snd/midiC0D0"  # fallback for host mode
+    return "/dev/snd/midiC0D0"
+

 def midi_msg(status, data1, data2=None):
    if data2 is not None:
        return f"midi {status} {data1} {data2};"
    return f"midi {status} {data1};"

+
 def _open_midi():
    midi_dev = _find_midi_dev()
    while not os.path.exists(midi_dev):
@@ -44,9 +59,102 @@ def _open_midi():
    os.set_blocking(fd, False)
    return fd

-def main():
-    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

+def _flush(sock, buf):
+    global midi_notes_on, midi_notes_off, midi_messages_total, midi_errors
+    global last_status, last_note, last_velocity, last_time
+
+    status = buf[0]
+    if (buf[0] & 0xF0) == 0xF0:
+        return
+    status = (status & 0xF0) | 0
+    data1 = buf[1]
+    data2 = buf[2] if len(buf) >= 3 else None
+    msg = midi_msg(status, data1, data2)
+    sock.sendto(msg.encode(), (PD_HOST, PD_PORT))
+    sock.sendto(msg.encode(), (PD_HOST, VIZ_PORT))
+
+    with _metrics_lock:
+        midi_messages_total += 1
+        last_status = status
+        last_note = data1
+        last_velocity = data2 if data2 is not None else 0
+        last_time = time.time()
+        msg_type = status & 0xF0
+        if msg_type == 0x90 and (data2 or 0) > 0:
+            midi_notes_on += 1
+        elif msg_type == 0x80 or (msg_type == 0x90 and (data2 or 0) == 0):
+            midi_notes_off += 1
+
+
+# ── Prometheus HTTP ──
+
+def _format_metrics():
+    with _metrics_lock:
+        lines = [
+            "# HELP midi_messages_total Total MIDI messages received",
+            "# TYPE midi_messages_total counter",
+            f"midi_messages_total {midi_messages_total}",
+            "",
+            "# HELP midi_notes_on_total Total note-on messages",
+            "# TYPE midi_notes_on_total counter",
+            f"midi_notes_on_total {midi_notes_on}",
+            "",
+            "# HELP midi_notes_off_total Total note-off messages",
+            "# TYPE midi_notes_off_total counter",
+            f"midi_notes_off_total {midi_notes_off}",
+            "",
+            "# HELP midi_errors_total Total MIDI parse errors",
+            "# TYPE midi_errors_total counter",
+            f"midi_errors_total {midi_errors}",
+            "",
+            "# HELP midi_last_status Status byte of last message",
+            "# TYPE midi_last_status gauge",
+            f"midi_last_status {last_status}",
+            "",
+            "# HELP midi_last_note Note number of last message",
+            "# TYPE midi_last_note gauge",
+            f"midi_last_note {last_note}",
+            "",
+            "# HELP midi_last_velocity Velocity of last message",
+            "# TYPE midi_last_velocity gauge",
+            f"midi_last_velocity {last_velocity}",
+            "",
+            "# HELP midi_last_time_unix Epoch of last MIDI message",
+            "# TYPE midi_last_time_unix gauge",
+            f"midi_last_time_unix {last_time:.3f}",
+            "",
+        ]
+    return "\n".join(lines) + "\n"
+
+
+class _MetricsHandler(http.server.BaseHTTPRequestHandler):
+    def do_GET(self):
+        if self.path == "/metrics":
+            body = _format_metrics().encode()
+            self.send_response(200)
+            self.send_header("Content-Type", "text/plain; version=0.0.4; charset=utf-8")
+            self.send_header("Content-Length", str(len(body)))
+            self.end_headers()
+            self.wfile.write(body)
+        else:
+            self.send_response(404)
+            self.end_headers()
+
+    def log_message(self, format, *args):
+        pass
+
+
+def _start_metrics_server():
+    server = http.server.HTTPServer(("0.0.0.0", METRICS_PORT), _MetricsHandler)
+    t = threading.Thread(target=server.serve_forever, daemon=True)
+    t.start()
+
+
+def main():
+    _start_metrics_server()
+
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    running = True
    while running:
        try:
@@ -90,16 +198,6 @@ def main():

    sock.close()

-def _flush(sock, buf):
-    status = buf[0]
-    if (buf[0] & 0xF0) == 0xF0:
-        return
-    status = (status & 0xF0) | 0  # normalize to channel 1
-    data1 = buf[1]
-    data2 = buf[2] if len(buf) >= 3 else None
-    msg = midi_msg(status, data1, data2)
-    sock.sendto(msg.encode(), (PD_HOST, PD_PORT))
-    sock.sendto(msg.encode(), (PD_HOST, VIZ_PORT))

 if __name__ == "__main__":
    main()