073f293cc3
* Change reference links for tacker source code from [1] to [2]. * Update broken links for Python Paste. [1] https://opendev.org/openstack/tacker/tree/ [2] https://opendev.org/openstack/tacker/src/branch/master Change-Id: I2e95faf2584f78a1f8694486d3ffd8a596109133 Closes-Bug: #1889200
61 lines
2.2 KiB
ReStructuredText
61 lines
2.2 KiB
ReStructuredText
Tacker WSGI/HTTP API layer
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===========================
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This section will cover the internals of Tacker's HTTP API, and the classes
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in Tacker that can be used to create Extensions to the Tacker 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 <https://legacy.python.org/dev/peps/pep-0333/>`_
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Startup
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-------
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Tackers's WSGI server is started from the `server module <https://opendev.org/openstack/tacker/src/branch/master/tacker/service.py>`_
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and the entry point `serve_wsgi` is called to build an instance of the
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`TackerApiService`_, 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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.. _TackerApiService: https://opendev.org/openstack/tacker/src/branch/master/tacker/service.py
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.. _Eventlet: https://eventlet.net/
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.. _GreenPool: https://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 TackerApiService, 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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Tacker, which contains several methods that map VNFM resources (such as
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vnfd, vnf) to URLs, and the controller for each resource.
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.. _config.py: https://opendev.org/openstack/tacker/src/branch/master/tacker/common/config.py
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.. _api-paste.ini: https://opendev.org/openstack/tacker/src/branch/master/etc/tacker/api-paste.ini
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.. _APIRouter: https://opendev.org/openstack/tacker/src/branch/master/tacker/api/v1/router.py
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.. _Paste: https://pythonpaste.readthedocs.io/
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.. _Deploy: https://pastedeploy.readthedocs.io/
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.. _Paste INI file format: https://pastedeploy.readthedocs.io/#applications
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Further reading
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---------------
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Tacker wsgi is based on neutron's extension. The following doc is still
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relevant.
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`Yong Sheng Gong: Deep Dive into Neutron <http://www.slideshare.net/gongys2004/inside-neutron-2>`_
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