Sync eventlet_backdoor from oslo-incubator

Includes this commit:

 c7c55b2 Improve usability when backdoor_port is nonzero

Change-Id: I06c0af7179bc2d0078e2cb757bef8551d8ce8b77

etc/nova/nova.conf.sample

@@ -1365,7 +1365,14 @@
 # Options defined in nova.openstack.common.eventlet_backdoor
 #
 
-# port for eventlet backdoor to listen (integer value)
+# Enable eventlet backdoor. Acceptable values are 0, <port>
+# and <start>:<end>, where 0 results in listening on a random
+# tcp port number, <port> results in listening on the
+# specified port number and not enabling backdoorif it is in
+# use and <start>:<end> results in listening on the smallest
+# unused port number within the specified range of port
+# numbers. The chosen port is displayed in the service's log
+# file. (string value)
 #backdoor_port=<None>
 
 

nova/openstack/common/eventlet_backdoor.py

@@ -18,8 +18,11 @@
 
 from __future__ import print_function
 
+import errno
 import gc
+import os
 import pprint
+import socket
 import sys
 import traceback
 
@@ -28,14 +31,34 @@ import eventlet.backdoor
 import greenlet
 from oslo.config import cfg
 
+from nova.openstack.common.gettextutils import _
+from nova.openstack.common import log as logging
+
+help_for_backdoor_port = 'Acceptable ' + \
+    'values are 0, <port> and <start>:<end>, where 0 results in ' + \
+    'listening on a random tcp port number, <port> results in ' + \
+    'listening on the specified port number and not enabling backdoor' + \
+    'if it is in use and <start>:<end> results in listening on the ' + \
+    'smallest unused port number within the specified range of port ' + \
+    'numbers. The chosen port is displayed in the service\'s log file.'
 eventlet_backdoor_opts = [
-    cfg.IntOpt('backdoor_port',
+    cfg.StrOpt('backdoor_port',
                default=None,
-               help='port for eventlet backdoor to listen')
+               help='Enable eventlet backdoor. %s' % help_for_backdoor_port)
 ]
 
 CONF = cfg.CONF
 CONF.register_opts(eventlet_backdoor_opts)
+LOG = logging.getLogger(__name__)
+
+
+class EventletBackdoorConfigValueError(Exception):
+    def __init__(self, port_range, help_msg, ex):
+        msg = ('Invalid backdoor_port configuration %(range)s: %(ex)s. '
+               '%(help)s' %
+               {'range': port_range, 'ex': ex, 'help': help_msg})
+        super(EventletBackdoorConfigValueError, self).__init__(msg)
+        self.port_range = port_range
 
 
 def _dont_use_this():
@@ -60,6 +83,33 @@ def _print_nativethreads():
         print()
 
 
+def _parse_port_range(port_range):
+    if ':' not in port_range:
+        start, end = port_range, port_range
+    else:
+        start, end = port_range.split(':', 1)
+    try:
+        start, end = int(start), int(end)
+        if end < start:
+            raise ValueError
+        return start, end
+    except ValueError as ex:
+        raise EventletBackdoorConfigValueError(port_range, ex,
+                                               help_for_backdoor_port)
+
+
+def _listen(host, start_port, end_port, listen_func):
+    try_port = start_port
+    while True:
+        try:
+            return listen_func((host, try_port))
+        except socket.error as exc:
+            if (exc.errno != errno.EADDRINUSE or
+               try_port >= end_port):
+                raise
+            try_port += 1
+
+
 def initialize_if_enabled():
     backdoor_locals = {
         'exit': _dont_use_this,      # So we don't exit the entire process
@@ -72,6 +122,8 @@ def initialize_if_enabled():
     if CONF.backdoor_port is None:
         return None
 
+    start_port, end_port = _parse_port_range(str(CONF.backdoor_port))
+
     # NOTE(johannes): The standard sys.displayhook will print the value of
     # the last expression and set it to __builtin__._, which overwrites
     # the __builtin__._ that gettext sets. Let's switch to using pprint
@@ -82,8 +134,13 @@ def initialize_if_enabled():
             pprint.pprint(val)
     sys.displayhook = displayhook
 
-    sock = eventlet.listen(('localhost', CONF.backdoor_port))
+    sock = _listen('localhost', start_port, end_port, eventlet.listen)
+
+    # In the case of backdoor port being zero, a port number is assigned by
+    # listen().  In any case, pull the port number out here.
     port = sock.getsockname()[1]
+    LOG.info(_('Eventlet backdoor listening on %(port)s for process %(pid)d') %
+             {'port': port, 'pid': os.getpid()})
     eventlet.spawn_n(eventlet.backdoor.backdoor_server, sock,
                      locals=backdoor_locals)
     return port