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This provides a brief explanation of the new nova-api-wsgi [1] and nova-metadata-wsgi [2] scripts in the Architecture section of the devref with links to the new doc added to the man pages for the eventlet scripts. The nova-api.rst mentioned ec2 so figured best to fix that now rather than forget about it, despite not being entirely germane. There is also a reno note that indicates the availability of the new scripts. There is a devstack change which is testing the new wsgi scripts as well as forcing grenade to not use them at If2d7e363a6541854f2e30c03171bef7a41aff745 [1] I7c4acfaa6c50ac0e4d6de69eb62ec5bbad72ff85 [2] Icb35fe2b94ab02c0ba8ba8129ae18aae0f794756 Change-Id: I351b2af3b256d3031bd2a65feba0495e815f8427 Related-Bug: #1661360
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Using WSGI with Nova
Though the compute and metadata APIs can be run using independent scripts that provide eventlet-based HTTP servers, it is generally considered more performant and flexible to run them using a generic HTTP server that supports WSGI (such as Apache or nginx).
The nova project provides two automatically generated entry points
that support this: nova-api-wsgi and
nova-metadata-wsgi. These read nova.conf and
api-paste.ini and generate the required module-level
application that most WSGI servers require. If nova is
installed using pip, these two scripts will be installed into whatever
the expected bin directory is for the environment.
The new scripts replace older experimental scripts that could be
found in the nova/wsgi directory of the code repository.
The new scripts are not experimental.
When running the compute and metadata services with WSGI, sharing the compute and metadata service in the same process is not supported (as it is in the eventlet-based scripts).
In devstack as of May 2017, the compute and metadata APIs are hosted by a Apache communicating with uwsgi via mod_proxy_uwsgi. Inspecting the configuration created there can provide some guidance on one option for managing the WSGI scripts. It is important to remember, however, that one of the major features of using WSGI is that there are many different ways to host a WSGI application. Different servers make different choices about performance and configurability.