add general signal handlers

A cloud-init job (user-data) might invoke /sbin/reboot or in some other
way end up killing cloud-init.  Rather than spewing the stack trace,
we just print a nicer message.

bin/cloud-init

@@ -35,6 +35,7 @@ if os.path.exists(os.path.join(possible_topdir, "cloudinit", "__init__.py")):
 
 from cloudinit import log as logging
 from cloudinit import netinfo
+from cloudinit import signal_handler
 from cloudinit import sources
 from cloudinit import stages
 from cloudinit import templater
@@ -494,6 +495,9 @@ def main():
     if args.debug:
         logging.setupBasicLogging()
 
+    # Setup signal handlers before running
+    signal_handler.attach_handlers()
+
     (name, functor) = args.action
     return functor(name, args)
 

cloudinit/signal_handler.py

@@ -0,0 +1,71 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Canonical Ltd.
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Scott Moser <scott.moser@canonical.com>
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import inspect
+import signal
+import sys
+
+from StringIO import StringIO
+
+from cloudinit import log as logging
+from cloudinit import util
+from cloudinit import version as vr
+
+LOG = logging.getLogger(__name__)
+
+
+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),
+}
+
+
+def _pprint_frame(frame, depth, max_depth, contents):
+    if depth > max_depth or not frame:
+        return
+    frame_info = inspect.getframeinfo(frame)
+    prefix = " " * (depth * 2)
+    contents.write("%sFilename: %s\n" % (prefix, frame_info.filename))
+    contents.write("%sFunction: %s\n" % (prefix, frame_info.function))
+    contents.write("%sLine number: %s\n" % (prefix, frame_info.lineno))
+    _pprint_frame(frame.f_back, depth + 1, max_depth, contents)
+
+
+def _handle_exit(signum, frame):
+    (msg, rc) = EXIT_FOR[signum]
+    msg = msg % ({'version': vr.version()})
+    contents = StringIO()
+    contents.write("%s\n" % (msg))
+    _pprint_frame(frame, 1, BACK_FRAME_TRACE_DEPTH, contents)
+    util.multi_log(contents.getvalue(),
+                   console=True, stderr=False, log=LOG)
+    sys.exit(rc)
+
+
+def attach_handlers():
+    sigs_attached = 0
+    for signum in EXIT_FOR.keys():
+        signal.signal(signum, _handle_exit)
+    sigs_attached += len(EXIT_FOR)
+    return sigs_attached