15342 FIX systemd_units_*_summary: Support units without description

The parser assumed that there is always a description, but systemd seems
to be okay with units without description.

The units were still detected but some service details were missing, for
example how long the service was in a temporary state.

Change-Id: I424e4dedb7144668f885ec1574b74fda135d7315

.werks/15342.md

@@ -0,0 +1,18 @@
+[//]: # (werk v2)
+# systemd_units_*_summary: Support units without description
+
+key        | value
+---------- | ---
+date       | 2024-08-20T13:41:37+00:00
+version    | 2.3.0p25
+class      | fix
+edition    | cre
+component  | checks
+level      | 1
+compatible | yes
+
+The parser assumed that there is always a description, but systemd seems to be
+okay with units without description.
+
+The units were still detected but some service details were missing, for example
+how long the service was in a temporary state.

cmk/base/plugins/agent_based/systemd_units.py

@@ -2,6 +2,7 @@
 # Copyright (C) 2022 Checkmk GmbH - License: GNU General Public License v2
 # This file is part of Checkmk (https://checkmk.com). It is subject to the terms and
 # conditions defined in the file COPYING, which is part of this source code package.
+import re
 from collections import defaultdict
 from collections.abc import Iterable, Iterator, Mapping, Sequence
 from dataclasses import dataclass
@@ -303,6 +304,12 @@ def _is_service_entry(entry: Sequence[Sequence[str]]) -> bool:
     return unit.endswith(".service")
 
 
+SERVICE_REGEX = re.compile(
+    r".+\.(service|socket|device|mount|automount|swap|target|path|timer|slice|scope)$"
+)
+# hopefully all possible unit types as described in https://www.freedesktop.org/software/systemd/man/latest/systemd.unit.html#Description
+
+
 def _is_new_entry(line: Sequence[str], entry: list[Sequence[str]]) -> bool:
     # First check if we're not looking at a "Triggers" section.
     # It looks like the beginning of a new status entry, e.g.:
@@ -313,7 +320,11 @@ def _is_new_entry(line: Sequence[str], entry: list[Sequence[str]]) -> bool:
             return False
         if elem[0] not in _STATUS_SYMBOLS:
             break
-    return (line[0] in _STATUS_SYMBOLS) and (len(line) > 3) and ("." in line[1])
+    return (
+        (line[0] in _STATUS_SYMBOLS)
+        and (len(line) >= 2)
+        and (bool(SERVICE_REGEX.match(str(line[1]))))
+    )
 
 
 def _parse_status(source: Iterator[Sequence[str]]) -> Mapping[str, UnitStatus]:

tests/unit/cmk/base/plugins/agent_based/test_systemd_units.py

@@ -1291,3 +1291,48 @@ def test_reloading() -> None:
             summary="Service 'testing' reloading for: 53 seconds (warn/crit at 30 seconds/1 minute 0 seconds)",
         ),
     ]
+
+
+def test_broken_parsing_without_unit_description() -> None:
+    pre_pre_string_table = """
+<<<systemd_units>>>
+[list-unit-files]
+testing.service enabled enabled
+systemd-user-sessions.service static -
+[status]
+● klapp-0285
+State: running
+Jobs: 1 queued
+Failed: 0 units
+Since: Mon 2024-08-19 07:09:27 CEST; 1 day 4h ago
+CGroup: /
+├─sys-fs-fuse-connections.mount
+
+● systemd-user-sessions.service - Permit User Sessions
+Loaded: loaded (/lib/systemd/system/systemd-user-sessions.service; static)
+Active: active (exited) since Mon 2024-08-19 07:09:30 CEST; 1 day 4h ago
+Docs: man:systemd-user-sessions.service(8)
+Main PID: 1397 (code=exited, status=0/SUCCESS)
+CPU: 6ms
+
+↻ testing.service
+Loaded: loaded (/etc/systemd/system/testing.service; enabled; vendor preset: enabled)
+Active: reloading (reload) since Tue 2024-08-20 11:49:32 CEST; 53s ago
+Process: 1727884 ExecStartPre=/usr/bin/sleep 75 (code=exited, status=0/SUCCESS)
+Main PID: 1728726 (sleep); Control PID: 1729357 (sleep)
+Tasks: 2 (limit: 38119)
+Memory: 360.0K
+CPU: 8ms
+CGroup: /system.slice/testing.service
+├─1728726 /usr/bin/sleep 90000
+└─1729357 /usr/bin/sleep 65
+
+[all]
+testing.service loaded reloading reload reload testing.service
+systemd-user-sessions.service loaded active exited Permit User Sessions
+"""
+
+    string_table = [l.split(" ") for l in pre_pre_string_table.split("\n")]
+    parsed = parse(string_table)
+    assert parsed is not None
+    assert parsed.services["testing"].time_since_change == timedelta(seconds=53)