sync oslo service to fix SIGHUP handling

this is a sync of the oslo service code to fix a bug found in
the sighup handling. Previously it was not possible to use
devstack's unstack.sh because the service module would always
restart under a SIGHUP, not only when the process was running as
a service. SIGHUP on a non-detached process should act like
SIGTERM. This change fixes that.

Change-Id: Ib260d82519fde5c5cb24a2c0c8a7cccd0b96b84f
Related-Bug: #1263122

nova/openstack/common/service.py

@@ -1,5 +1,3 @@
-# vim: tabstop=4 shiftwidth=4 softtabstop=4
-
 # Copyright 2010 United States Government as represented by the
 # Administrator of the National Aeronautics and Space Administration.
 # Copyright 2011 Justin Santa Barbara
@@ -20,15 +18,23 @@
 """Generic Node base class for all workers that run on hosts."""
 
 import errno
+import logging as std_logging
 import os
 import random
 import signal
 import sys
 import time
 
+try:
+    # Importing just the symbol here because the io module does not
+    # exist in Python 2.6.
+    from io import UnsupportedOperation  # noqa
+except ImportError:
+    # Python 2.6
+    UnsupportedOperation = None
+
 import eventlet
 from eventlet import event
-import logging as std_logging
 from oslo.config import cfg
 
 from nova.openstack.common import eventlet_backdoor
@@ -47,8 +53,32 @@ def _sighup_supported():
     return hasattr(signal, 'SIGHUP')
 
 
-def _is_sighup(signo):
-    return _sighup_supported() and signo == signal.SIGHUP
+def _is_daemon():
+    # The process group for a foreground process will match the
+    # process group of the controlling terminal. If those values do
+    # not match, or ioctl() fails on the stdout file handle, we assume
+    # the process is running in the background as a daemon.
+    # http://www.gnu.org/software/bash/manual/bashref.html#Job-Control-Basics
+    try:
+        is_daemon = os.getpgrp() != os.tcgetpgrp(sys.stdout.fileno())
+    except OSError as err:
+        if err.errno == errno.ENOTTY:
+            # Assume we are a daemon because there is no terminal.
+            is_daemon = True
+        else:
+            raise
+    except UnsupportedOperation:
+        # Could not get the fileno for stdout, so we must be a daemon.
+        is_daemon = True
+    return is_daemon
+
+
+def _is_sighup_and_daemon(signo):
+    if not (_sighup_supported() and signo == signal.SIGHUP):
+        # Avoid checking if we are a daemon, because the signal isn't
+        # SIGHUP.
+        return False
+    return _is_daemon()
 
 
 def _signo_to_signame(signo):
@@ -129,7 +159,7 @@ class ServiceLauncher(Launcher):
     def handle_signal(self):
         _set_signals_handler(self._handle_signal)
 
-    def _wait_for_exit_or_signal(self):
+    def _wait_for_exit_or_signal(self, ready_callback=None):
         status = None
         signo = 0
 
@@ -137,6 +167,8 @@ class ServiceLauncher(Launcher):
         CONF.log_opt_values(LOG, std_logging.DEBUG)
 
         try:
+            if ready_callback:
+                ready_callback()
             super(ServiceLauncher, self).wait()
         except SignalExit as exc:
             signame = _signo_to_signame(exc.signo)
@@ -156,11 +188,11 @@ class ServiceLauncher(Launcher):
 
         return status, signo
 
-    def wait(self):
+    def wait(self, ready_callback=None):
         while True:
             self.handle_signal()
-            status, signo = self._wait_for_exit_or_signal()
-            if not _is_sighup(signo):
+            status, signo = self._wait_for_exit_or_signal(ready_callback)
+            if not _is_sighup_and_daemon(signo):
                 return status
             self.restart()
 
@@ -218,7 +250,7 @@ class ProcessLauncher(object):
         signal.signal(signal.SIGINT, signal.SIG_IGN)
 
     def _child_wait_for_exit_or_signal(self, launcher):
-        status = None
+        status = 0
         signo = 0
 
         # NOTE(johannes): All exceptions are caught to ensure this
@@ -280,7 +312,7 @@ class ProcessLauncher(object):
             while True:
                 self._child_process_handle_signal()
                 status, signo = self._child_wait_for_exit_or_signal(launcher)
-                if not _is_sighup(signo):
+                if not _is_sighup_and_daemon(signo):
                     break
                 launcher.restart()
 
@@ -352,7 +384,7 @@ class ProcessLauncher(object):
             if self.sigcaught:
                 signame = _signo_to_signame(self.sigcaught)
                 LOG.info(_('Caught %s, stopping children'), signame)
-            if not _is_sighup(self.sigcaught):
+            if not _is_sighup_and_daemon(self.sigcaught):
                 break
 
             for pid in self.children: