Add a Python script to parse Chrony NTP clients

Use the output of `chronyc -c tracking` to provide some basic NTP client
status metrics.

Signed-off-by: SuperQ <[email protected]>

Author: SuperQ

Diff for: chrony.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+#
+# Description: Gather metrics from Chrony NTP.
+#
+
+import subprocess
+import sys
+
+from prometheus_client import CollectorRegistry, Gauge, generate_latest
+
+
+def chronyc(*args, check=True):
+    """Chrony client wrapper
+
+    Returns:
+       (str) Data piped to stdout by the chrony subprocess.
+    """
+    return subprocess.run(
+        ['chronyc', *args], stdout=subprocess.PIPE, check=check
+    ).stdout.decode('utf-8')
+
+
+def chronyc_tracking():
+    return chronyc('-c', 'tracking').split(',')
+
+
+def main():
+    registry = CollectorRegistry()
+    chrony_tracking = chronyc_tracking()
+
+    if len(chrony_tracking) != 14:
+        print("ERROR: Unable to parse chronyc tracking CSV", file=sys.stderr)
+        sys.exit(1)
+
+    g = Gauge('chrony_tracking_reference_info',
+              'The stratum of the current preferred source',
+              ['ref_id', 'ref_host'],
+              registry=registry)
+    g.labels(chrony_tracking[0], chrony_tracking[1]).set(1)
+
+    g = Gauge('chrony_tracking_stratum',
+              'The stratum of the current preferred source',
+              registry=registry)
+    g.set(chrony_tracking[2])
+
+    g = Gauge('chrony_tracking_system_offset_seconds',
+              'The current estimated drift of system time from true time',
+              registry=registry)
+    g.set(chrony_tracking[4])
+
+    g = Gauge('chrony_tracking_last_offset_seconds',
+              'The estimated local offset on the last clock update.',
+              registry=registry)
+    g.set(chrony_tracking[5])
+
+    g = Gauge('chrony_tracking_root_dispersion_seconds',
+              'The absolute bound on the computer’s clock accuracy',
+              registry=registry)
+    g.set(chrony_tracking[5])
+
+    print(generate_latest(registry).decode("utf-8"), end='')
+
+
+if __name__ == "__main__":
+    main()