fix: uninstall custom signal handlers before shutdown

cloudinit/config/cc_package_update_upgrade_install.py

@@ -10,7 +10,7 @@
 import os
 import time
 
-from cloudinit import subp, util
+from cloudinit import signal_handler, subp, util
 from cloudinit.cloud import Cloud
 from cloudinit.config import Config
 from cloudinit.config.schema import MetaSchema
@@ -48,6 +48,9 @@ def _fire_reboot(
     wait_attempts: int = 6, initial_sleep: int = 1, backoff: int = 2
 ):
     """Run a reboot command and panic if it doesn't happen fast enough."""
+    # systemd will kill cloud-init with a signal
+    # this is expected so don't behave as if this is a failure state
+    signal_handler.detach_handlers()
     subp.subp(REBOOT_CMD)
     start = time.monotonic()
     wait_time = initial_sleep
@@ -106,8 +109,9 @@ def handle(name: str, cfg: Config, cloud: Cloud, args: list) -> None:
             break
     if (upgrade or pkglist) and reboot_if_required and reboot_fn_exists:
         try:
-            LOG.warning(
-                "Rebooting after upgrade or install per %s", reboot_marker
+            LOG.info(
+                "***WARNING*** Rebooting after upgrade or install per %s",
+                reboot_marker,
             )
             # Flush the above warning + anything else out...
             flush_loggers(LOG)

cloudinit/config/cc_power_state_change.py

@@ -13,7 +13,7 @@
 import subprocess
 import time
 
-from cloudinit import subp, util
+from cloudinit import signal_handler, subp, util
 from cloudinit.cloud import Cloud
 from cloudinit.config import Config
 from cloudinit.config.schema import MetaSchema
@@ -217,4 +217,7 @@ def fatal(msg):
     except Exception as e:
         fatal("Unexpected Exception when checking condition: %s" % e)
 
+    # systemd could kill this process with a signal before it exits
+    # this is expected, so remove the signal handlers
+    signal_handler.detach_handlers()
     func(*args)

cloudinit/signal_handler.py

@@ -10,20 +10,59 @@
 import signal
 import sys
 from io import StringIO
+from typing import Callable, Dict, NamedTuple, Union
 
 from cloudinit import version as vr
 from cloudinit.log import log_util
 
 LOG = logging.getLogger(__name__)
 
 
+class SignalType(NamedTuple):
+    message: str
+    exit_code: int
+    default_signal: Union[Callable, int, None]
+
+
+def default_handler(_num, _stack) -> None:
+    """an empty handler"""
+    return None
+
+
+def get_handler(sig: Union[int, Callable, None]) -> Callable:
+    """get_handler gets a callable from signal.signal() output."""
+    if callable(sig):
+        return sig
+    elif sig is None:
+        LOG.warning("Signal handler was not installed from Python!")
+    elif sig == signal.SIG_DFL:
+        LOG.warning("Signal was in unexpected state: SIG_DFL")
+    elif sig == signal.SIG_IGN:
+        LOG.warning("Signal was in unexpected state: SIG_IGN")
+    else:
+        LOG.warning(
+            "Process signal is in an unknown state: %s(%s)", type(sig), sig
+        )
+    return default_handler
+
+
 BACK_FRAME_TRACE_DEPTH = 3
-EXIT_FOR = {
-    signal.SIGINT: ("Cloud-init %(version)s received SIGINT, exiting...", 1),
-    signal.SIGTERM: ("Cloud-init %(version)s received SIGTERM, exiting...", 1),
-    # Can't be caught...
-    # signal.SIGKILL: ('Cloud-init killed, exiting...', 1),
-    signal.SIGABRT: ("Cloud-init %(version)s received SIGABRT, exiting...", 1),
+EXIT_FOR: Dict[int, SignalType] = {
+    signal.SIGINT: SignalType(
+        "Cloud-init %(version)s received SIGINT, exiting...",
+        1,
+        signal.getsignal(signal.SIGINT),
+    ),
+    signal.SIGTERM: SignalType(
+        "Cloud-init %(version)s received SIGTERM, exiting...",
+        1,
+        signal.getsignal(signal.SIGTERM),
+    ),
+    signal.SIGABRT: SignalType(
+        "Cloud-init %(version)s received SIGABRT, exiting...",
+        1,
+        signal.getsignal(signal.SIGABRT),
+    ),
 }
 
 
@@ -39,7 +78,7 @@ def _pprint_frame(frame, depth, max_depth, contents):
 
 
 def _handle_exit(signum, frame):
-    (msg, rc) = EXIT_FOR[signum]
+    msg, rc, _ = EXIT_FOR[signum]
     msg = msg % ({"version": vr.version_string()})
     contents = StringIO()
     contents.write("%s\n" % (msg))
@@ -49,8 +88,18 @@ def _handle_exit(signum, frame):
 
 
 def attach_handlers():
+    """attach cloud-init's handlers"""
     sigs_attached = 0
     for signum in EXIT_FOR.keys():
         signal.signal(signum, _handle_exit)
     sigs_attached += len(EXIT_FOR)
     return sigs_attached
+
+
+def detach_handlers():
+    """dettach cloud-init's handlers"""
+    sigs_attached = 0
+    for number, sig_type in EXIT_FOR.items():
+        signal.signal(number, get_handler(sig_type.default_signal))
+    sigs_attached += len(EXIT_FOR)
+    return sigs_attached

tests/unittests/config/test_cc_package_update_upgrade_install.py

@@ -121,7 +121,7 @@ def _isfile(filename: str):
                     # subp and not really rebooting the system
                     subp_call = ["/sbin/reboot"]
 
-        caplog.set_level(logging.WARNING)
+        caplog.set_level(logging.INFO)
         with mock.patch(
             "cloudinit.subp.subp", return_value=SubpResult("{}", "fakeerr")
         ) as m_subp: