wsgi: do not respawn on missing eventlet hub

Eventlet 'poll' hub is not available on OSX, wsgi.Server workers have no
chance to start but the error was not caught and they were respawned
endlessly. This patch makes these workers not to be respawned.

This has the nice side-effect of avoiding the test suite to get stuck in
test_multiprocessing on OSX, filling syslog.

Change-Id: I565d21f5c6861102e96d6953ace29cde57e8ec38

bin/glance-api

@@ -38,6 +38,12 @@ gettext.install('glance', unicode=1)
 
 from glance.common import config
 from glance.common import wsgi
+from glance.common import exception
+
+
+def fail(returncode, e):
+    sys.stderr.write("ERROR: %s\n" % e)
+    sys.exit(returncode)
 
 
 if __name__ == '__main__':
@@ -50,6 +56,7 @@ if __name__ == '__main__':
         server = wsgi.Server()
         server.start(app, conf, default_port=9292)
         server.wait()
+    except exception.WorkerCreationFailure, e:
+        fail(2, e)
     except RuntimeError, e:
-        sys.stderr.write("ERROR: %s\n" % e)
-        sys.exit(1)
+        fail(1, e)

glance/common/exception.py

@@ -232,3 +232,7 @@ class RegionAmbiguity(GlanceException):
     message = _("Multiple 'image' service matches for region %(region)s. This "
                 "generally means that a region is required and you have not "
                 "supplied one.")
+
+
+class WorkerCreationFailure(GlanceException):
+    message = _("Server worker creation failed: %(reason)s.")

glance/common/wsgi.py

@@ -192,7 +192,15 @@ class Server(object):
                 if os.WIFEXITED(status) or os.WIFSIGNALED(status):
                     self.logger.error(_('Removing dead child %s') % pid)
                     self.children.remove(pid)
-                    self.run_child()
+                    if os.WIFEXITED(status) and os.WEXITSTATUS(status) == 2:
+                        self.logger.error(_('Not respawning child %d, cannot '
+                                            'recover from termination') % pid)
+                        if not self.children:
+                            self.logger.error(
+                                _('All workers have terminated. Exiting'))
+                            self.running = False
+                    else:
+                        self.run_child()
             except OSError, err:
                 if err.errno not in (errno.EINTR, errno.ECHILD):
                     raise
@@ -232,7 +240,11 @@ class Server(object):
     def run_server(self):
         """Run a WSGI server."""
         eventlet.wsgi.HttpProtocol.default_request_version = "HTTP/1.0"
-        eventlet.hubs.use_hub('poll')
+        try:
+            eventlet.hubs.use_hub('poll')
+        except Exception:
+            msg = _("eventlet 'poll' hub is not available on this platform")
+            raise exception.WorkerCreationFailure(reason=msg)
         eventlet.patcher.monkey_patch(all=False, socket=True)
         self.pool = eventlet.GreenPool(size=self.threads)
         try: