Re-work how debugger CLI opts are registered

CLI options must be registered before the command line is parsed or a
cfg.ArgsAlreadyParsedError is raised.

Since commit 2cbea24 we are registering two 'remote_debug' arguments
in nova.service. In commit b506529, we see a hack being added to
ensure that nova.service is imported and the CLI opts registered
before config.parse_args() is called.

To clean this up somewhat, refactor all the elements of this remote
debugger support into nova.debugger. Avoid importing modules at
module import time since we need to import this before monkey
patching. Add a function for registering the CLI options just before
config.parse_args() is called. And fail gracefully if the CLI options
aren't registered when we called debugger.init().

Note that because the options aren't registered at module import time
any more, the config generator doesn't pick them up. However, that's
actually a good thing since this support doesn't work if you enable it
via config files since debugger.enabled() only looks at the command
line.

DocImpact: remote_debug options are not available via the config file,
only via the command line.

Change-Id: I97f747a2fb9222137203657df1d86ba89f3219e2

1 files changed, 80 insertions, 0 deletions

diff --git a/nova/debugger.py b/nova/debugger.py
new file mode 100644
index 0000000000..77ca74188d
--- /dev/null
+++ b/nova/debugger.py
@@ -0,0 +1,80 @@
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# Copyright 2011 Justin Santa Barbara
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+# NOTE(markmc): this is imported before monkey patching in nova.cmd
+# so we avoid extra imports here
+
+import sys
+
+
+def enabled():
+    return ('--remote_debug-host' in sys.argv and
+            '--remote_debug-port' in sys.argv)
+
+
+def register_cli_opts():
+    from oslo.config import cfg
+
+    cli_opts = [
+        cfg.StrOpt('host',
+                    help='Debug host (IP or name) to connect. Note '
+                        'that using the remote debug option changes how '
+                        'Nova uses the eventlet library to support async IO. '
+                        'This could result in failures that do not occur '
+                        'under normal operation. Use at your own risk.'),
+
+        cfg.IntOpt('port',
+                    help='Debug port to connect. Note '
+                        'that using the remote debug option changes how '
+                        'Nova uses the eventlet library to support async IO. '
+                        'This could result in failures that do not occur '
+                        'under normal operation. Use at your own risk.')
+
+    ]
+
+    cfg.CONF.register_cli_opts(cli_opts, 'remote_debug')
+
+
+def init():
+    from oslo.config import cfg
+    CONF = cfg.CONF
+
+    # NOTE(markmc): gracefully handle the CLI options not being registered
+    if 'remote_debug' not in CONF:
+        return
+
+    if not (CONF.remote_debug.host and CONF.remote_debug.port):
+        return
+
+    from nova.openstack.common.gettextutils import _
+    from nova.openstack.common import log as logging
+    LOG = logging.getLogger(__name__)
+
+    LOG.debug(_('Listening on %(host)s:%(port)s for debug connection'),
+              {'host': CONF.remote_debug.host,
+               'port': CONF.remote_debug.port})
+
+    from pydev import pydevd
+    pydevd.settrace(host=CONF.remote_debug.host,
+                    port=CONF.remote_debug.port,
+                    stdoutToServer=False,
+                    stderrToServer=False)
+
+    LOG.warn(_('WARNING: Using the remote debug option changes how '
+               'Nova uses the eventlet library to support async IO. This '
+               'could result in failures that do not occur under normal '
+               'operation. Use at your own risk.'))