81 lines
2.9 KiB
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81 lines
2.9 KiB
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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Convention for heading levels in Neutron devref:
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======= Heading 0 (reserved for the title in a document)
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------- Heading 1
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~~~~~~~ Heading 2
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+++++++ Heading 3
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''''''' Heading 4
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(Avoid deeper levels because they do not render well.)
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Neutron WSGI/HTTP API layer
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===========================
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This section will cover the internals of Neutron's HTTP API, and the classes
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in Neutron that can be used to create Extensions to the Neutron API.
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Python web applications interface with webservers through the Python Web
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Server Gateway Interface (WSGI) - defined in `PEP 333 <http://legacy.python.org/dev/peps/pep-0333/>`_
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Startup
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-------
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Neutron's WSGI server is started from the `server module <http://opendev.org/openstack/neutron/src/neutron/server/__init__.py>`_
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and the entry point `serve_wsgi` is called to build an instance of the
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`NeutronApiService`_, which is then returned to the server module,
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which spawns a `Eventlet`_ `GreenPool`_ that will run the WSGI
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application and respond to requests from clients.
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.. _NeutronApiService: http://opendev.org/openstack/neutron/src/neutron/service.py
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.. _Eventlet: http://eventlet.net/
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.. _GreenPool: http://eventlet.net/doc/modules/greenpool.html
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WSGI Application
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----------------
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During the building of the NeutronApiService, the `_run_wsgi` function
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creates a WSGI application using the `load_paste_app` function inside
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`config.py`_ - which parses `api-paste.ini`_ - in order to create a WSGI app
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using `Paste`_'s `deploy`_.
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The api-paste.ini file defines the WSGI applications and routes - using the
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`Paste INI file format`_.
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The INI file directs paste to instantiate the `APIRouter`_ class of
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Neutron, which contains several methods that map Neutron resources (such as
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Ports, Networks, Subnets) to URLs, and the controller for each resource.
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.. _config.py: http://opendev.org/openstack/neutron/src/neutron/common/config.py
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.. _api-paste.ini: http://opendev.org/openstack/neutron/src/etc/api-paste.ini
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.. _APIRouter: http://opendev.org/openstack/neutron/src/neutron/api/v2/router.py
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.. _Paste: http://pythonpaste.org/
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.. _Deploy: http://pythonpaste.org/deploy/
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.. _Paste INI file format: http://pythonpaste.org/deploy/#applications
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Further reading
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---------------
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`Yong Sheng Gong: Deep Dive into Neutron <http://www.slideshare.net/gongys2004/inside-neutron-2>`_
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