Adding a means for a glance worker to connect back to a pydevd debugger.

That patch allows a developer to remotely run a pydev debugger and a
glance worker process connect back to it.  Two configuration options
have been added:
    pydev_worker_debug_host <host>. Default is None
    pydev_worker_debug_port <port>. Default is 5678
The behavior is enabled if pydev_worker_debug_host is not None.  If
a pydev connection fails to be esstablished an exception is raised.

This patch will allow remote debugging as well as more seemless
debugging environments with IDEs like pycharm.

Change-Id: I7d3f60e373632b256f0e914f18204ce223a3486e

glance/common/config.py

@@ -58,6 +58,12 @@ common_opts = [
                 help=_("Deploy the v1 OpenStack Images API. ")),
     cfg.BoolOpt('enable_v2_api', default=True,
                 help=_("Deploy the v2 OpenStack Images API. ")),
+    cfg.StrOpt('pydev_worker_debug_host', default=None,
+               help=_('The hostname/IP of the pydev process listening for '
+                      'debug connections')),
+    cfg.IntOpt('pydev_worker_debug_port', default=5678,
+               help=_('The port on which a pydev process is listening for '
+                      'connections.')),
 ]
 
 CONF = cfg.CONF

glance/common/utils.py

@@ -36,6 +36,7 @@ import sys
 from webob import exc
 
 from glance.common import exception
+from glance.openstack.common import cfg
 import glance.openstack.common.log as logging
 
 
@@ -410,3 +411,23 @@ def mutating(func):
                                     content_type="text/plain")
         return func(self, req, *args, **kwargs)
     return wrapped
+
+
+def setup_remote_pydev_debug(host, port):
+
+        error_msg = ('Error setting up the debug environment.  Verify that the'
+                     ' option pydev_worker_debug_port is pointing to a valid '
+                     'hostname or IP on which a pydev server is listening on'
+                     ' the port indicated by pydev_worker_debug_port.')
+
+        try:
+            from pydev import pydevd
+
+            pydevd.settrace(host,
+                            port=port,
+                            stdoutToServer=True,
+                            stderrToServer=True)
+            return True
+        except:
+            LOG.exception(error_msg)
+            raise

glance/common/wsgi.py

@@ -40,6 +40,7 @@ import webob.dec
 import webob.exc
 
 from glance.common import exception
+from glance.common import utils
 from glance.openstack.common import cfg
 import glance.openstack.common.log as os_logging
 
@@ -266,6 +267,10 @@ class Server(object):
 
     def run_server(self):
         """Run a WSGI server."""
+        if cfg.CONF.pydev_worker_debug_host:
+            utils.setup_remote_pydev_debug(cfg.CONF.pydev_worker_debug_host,
+                                           cfg.CONF.pydev_worker_debug_port)
+
         eventlet.wsgi.HttpProtocol.default_request_version = "HTTP/1.0"
         try:
             eventlet.hubs.use_hub('poll')