Add system and certificate telemetry collectors

collectors/certificates.py

@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+
+import subprocess
+from datetime import datetime, timezone
+from pathlib import Path
+
+CERT_ROOT = Path(
+    "/opt/docker/caddy/data/caddy/certificates/"
+    "acme-v02.api.letsencrypt.org-directory"
+)
+
+
+def collect():
+    certificates = []
+
+    for cert_file in sorted(CERT_ROOT.glob("*/*.crt")):
+        result = subprocess.run(
+            ["openssl", "x509", "-in", str(cert_file), "-noout", "-enddate"],
+            capture_output=True,
+            text=True,
+        )
+
+        if result.returncode != 0:
+            continue
+
+        expires_text = result.stdout.strip().removeprefix("notAfter=")
+        expires = datetime.strptime(
+            expires_text,
+            "%b %d %H:%M:%S %Y %Z",
+        ).replace(tzinfo=timezone.utc)
+
+        days_remaining = (expires - datetime.now(timezone.utc)).days
+
+        certificates.append({
+            "name": cert_file.parent.name,
+            "days_remaining": days_remaining,
+            "expires": expires.isoformat(),
+        })
+
+    if not certificates:
+        return {
+            "state": "offline",
+            "summary": "No certificates",
+            "detail": "Caddy certificate files not found",
+        }
+
+    lowest = min(item["days_remaining"] for item in certificates)
+
+    state = "online"
+    if lowest < 30:
+        state = "warning"
+    if lowest < 7:
+        state = "offline"
+
+    return {
+        "state": state,
+        "summary": f"{len(certificates)} certificates",
+        "detail": f"{lowest} days minimum",
+        "minimum_days": lowest,
+        "certificates": certificates,
+    }