Use werkzeug to run the developement API server

wsgi.simple_server in a mono threaded process that can handle only
5 requests at a time.

Even the doc recommands to setup Ceilometer through an other WSGI services
like Apache 'mod_wsgi', we can provide a better testing API server.

So this patch changes the default HTTP server to the werkzeug one with
a autodiscovery of number of workers that we can use.

The client queue of werkzeug is 128, so on a 4 cpus machine, ceilometer-api
can now handle 512 connections instead of 5.

Also the change adds references of how to deploy pecan application in
the documentation.

The config option enable_reverse_dns_lookup can be safely removed,
because werkzeug doesn't do any reverse dns lookup.

DocImpact: configuration options changed:
enable_reverse_dns_lookup removed, api_workers added

Change-Id: If7450b393ea88bc185e5c82b706ace9c38ce350e

ceilometer/api/__init__.py

@@ -27,12 +27,6 @@ OPTS = [
                default='0.0.0.0',
                help='The listen IP for the ceilometer API server.',
                ),
-    cfg.BoolOpt('enable_reverse_dns_lookup',
-                default=False,
-                help=('Set it to False if your environment does not need '
-                      'or have a DNS server, otherwise it will delay the '
-                      'response from the API.')
-                ),
 ]
 
 CONF = cfg.CONF

ceilometer/api/app.py

@@ -15,19 +15,20 @@
 
 import logging
 import os
-import socket
-from wsgiref import simple_server
 
-import netaddr
+
 from oslo_config import cfg
 from paste import deploy
 import pecan
+from werkzeug import serving
 
 from ceilometer.api import config as api_config
 from ceilometer.api import hooks
 from ceilometer.api import middleware
 from ceilometer.i18n import _
+from ceilometer.i18n import _LW
 from ceilometer.openstack.common import log
+from ceilometer import service
 from ceilometer import storage
 
 LOG = log.getLogger(__name__)
@@ -39,6 +40,8 @@ OPTS = [
                default="api_paste.ini",
                help="Configuration file for WSGI definition of API."
                ),
+    cfg.IntOpt('api_workers', default=1,
+               help='Number of workers for Ceilometer API server.'),
 ]
 
 API_OPTS = [
@@ -77,9 +80,16 @@ def setup_app(pecan_config=None, extra_hooks=None):
 
     cfg.set_defaults(API_OPTS, pecan_debug=CONF.debug)
 
+    # NOTE(sileht): pecan debug won't work in multi-process environment
+    pecan_debug = CONF.api.pecan_debug
+    if service.get_workers('api') != 1 and pecan_debug:
+        pecan_debug = False
+        LOG.warning(_LW('pecan_debug cannot be enabled, if workers is > 1, '
+                        'the value is overrided with False'))
+
     app = pecan.make_app(
         pecan_config.app.root,
-        debug=CONF.api.pecan_debug,
+        debug=pecan_debug,
         force_canonical=getattr(pecan_config.app, 'force_canonical', True),
         hooks=app_hooks,
         wrap_app=middleware.ParsableErrorMiddleware,
@@ -106,36 +116,6 @@ class VersionSelectorApplication(object):
         return self.v2(environ, start_response)
 
 
-def get_server_cls(host):
-    """Return an appropriate WSGI server class base on provided host
-
-    :param host: The listen host for the ceilometer API server.
-    """
-    server_cls = simple_server.WSGIServer
-    if netaddr.valid_ipv6(host):
-        # NOTE(dzyu) make sure use IPv6 sockets if host is in IPv6 pattern
-        if getattr(server_cls, 'address_family') == socket.AF_INET:
-            class ipv6_server_cls(server_cls):
-                address_family = socket.AF_INET6
-            return ipv6_server_cls
-    return server_cls
-
-
-def get_handler_cls():
-    cls = simple_server.WSGIRequestHandler
-
-    # old-style class doesn't support super
-    class CeilometerHandler(cls, object):
-        def address_string(self):
-            if cfg.CONF.api.enable_reverse_dns_lookup:
-                return super(CeilometerHandler, self).address_string()
-            else:
-                # disable reverse dns lookup, directly return ip address
-                return self.client_address[0]
-
-    return CeilometerHandler
-
-
 def load_app():
     # Build the WSGI app
     cfg_file = None
@@ -155,10 +135,6 @@ def build_server():
     app = load_app()
     # Create the WSGI server and start it
     host, port = cfg.CONF.api.host, cfg.CONF.api.port
-    server_cls = get_server_cls(host)
-
-    srv = simple_server.make_server(host, port, app,
-                                    server_cls, get_handler_cls())
 
     LOG.info(_('Starting server in PID %s') % os.getpid())
     LOG.info(_("Configuration:"))
@@ -172,7 +148,9 @@ def build_server():
         LOG.info(_("serving on http://%(host)s:%(port)s") % (
                  {'host': host, 'port': port}))
 
-    return srv
+    workers = service.get_workers('api')
+    serving.run_simple(cfg.CONF.api.host, cfg.CONF.api.port,
+                       app, processes=workers)
 
 
 def app_factory(global_config, **local_conf):

ceilometer/cmd/api.py

@@ -20,5 +20,4 @@ from ceilometer import service
 
 def main():
     service.prepare_service()
-    srv = app.build_server()
+    app.build_server()
-    srv.serve_forever()

ceilometer/tests/api/test_app.py

@@ -15,8 +15,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import socket
-
 import mock
 from oslo_config import cfg
 from oslo_config import fixture as fixture_config
@@ -31,19 +29,6 @@ class TestApp(base.BaseTestCase):
         super(TestApp, self).setUp()
         self.CONF = self.useFixture(fixture_config.Config()).conf
 
-    def test_WSGI_address_family(self):
-        self.CONF.set_override('host', '::', group='api')
-        server_cls = app.get_server_cls(cfg.CONF.api.host)
-        self.assertEqual(server_cls.address_family, socket.AF_INET6)
-
-        self.CONF.set_override('host', '127.0.0.1', group='api')
-        server_cls = app.get_server_cls(cfg.CONF.api.host)
-        self.assertEqual(server_cls.address_family, socket.AF_INET)
-
-        self.CONF.set_override('host', 'ddddd', group='api')
-        server_cls = app.get_server_cls(cfg.CONF.api.host)
-        self.assertEqual(server_cls.address_family, socket.AF_INET)
-
     def test_api_paste_file_not_exist(self):
         self.CONF.set_override('api_paste_config', 'non-existent-file')
         with mock.patch.object(self.CONF, 'find_file') as ff:
@@ -55,10 +40,11 @@ class TestApp(base.BaseTestCase):
     @mock.patch('ceilometer.api.hooks.PipelineHook', mock.MagicMock())
     @mock.patch('pecan.make_app')
     def test_pecan_debug(self, mocked):
-        def _check_pecan_debug(g_debug, p_debug, expected):
+        def _check_pecan_debug(g_debug, p_debug, expected, workers=1):
             self.CONF.set_override('debug', g_debug)
             if p_debug is not None:
                 self.CONF.set_override('pecan_debug', p_debug, group='api')
+            self.CONF.set_override('api_workers', workers)
             app.setup_app()
             args, kwargs = mocked.call_args
             self.assertEqual(expected, kwargs.get('debug'))
@@ -67,3 +53,7 @@ class TestApp(base.BaseTestCase):
         _check_pecan_debug(g_debug=True, p_debug=None, expected=True)
         _check_pecan_debug(g_debug=True, p_debug=False, expected=False)
         _check_pecan_debug(g_debug=False, p_debug=True, expected=True)
+        _check_pecan_debug(g_debug=True, p_debug=None, expected=False,
+                           workers=5)
+        _check_pecan_debug(g_debug=False, p_debug=True, expected=False,
+                           workers=5)

doc/source/install/mod_wsgi.rst

@@ -63,3 +63,6 @@ multiple processes, there is no way to set debug mode in the multiprocessing
 case. To allow multiple processes the DebugMiddleware may be turned off by
 setting ``pecan_debug`` to ``False`` in the ``api`` section of
 ``ceilometer.conf``.
+
+For other WSGI setup you can refer to the `pecan deployement`_ documentation.
+.. _`pecan deployement`: http://pecan.readthedocs.org/en/latest/deployment.html#deployment

requirements.txt

@@ -44,5 +44,6 @@ SQLAlchemy>=0.9.7,<=0.9.99
 sqlalchemy-migrate>=0.9.1,!=0.9.2
 stevedore>=1.1.0  # Apache-2.0
 tooz>=0.3 # Apache-2.0
+werkzeug>=0.7  # BSD License
 WebOb>=1.2.3
 WSME>=0.6