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Description:

microversionparse 1.0.1

A small set of functions to manage OpenStack microversion headers that can
be used in middleware, application handlers and decorators to effectively
manage microversions.
Also included, in the middleware module, is a MicroversionMiddleware
that will process incoming microversion headers.

get_version
A simple parser for OpenStack microversion headers:
import microversion_parse

# headers is a dict of headers with folded (comma-separated
# values) or a list of header, value tuples
version = microversion_parse.get_version(
headers, service_type='compute',
legacy_headers=['x-openstack-nova-api-version'])

# If headers are not already available, a dict of headers
# can be extracted from the WSGI environ
headers = microversion_parse.headers_from_wsgi_environ(environ)
version = microversion_parse.get_version(
headers, service_type='placement')
It processes microversion headers with the standard form:
OpenStack-API-Version: compute 2.1
In that case, the response will be ‘2.1’.
If provided with a legacy_headers argument, this is treated as
a list of additional headers to check for microversions. Some examples of
headers include:
OpenStack-telemetry-api-version: 2.1
OpenStack-nova-api-version: 2.1
X-OpenStack-nova-api-version: 2.1
If a version string cannot be found, None will be returned. If
the input is incorrect usual Python exceptions (ValueError,
TypeError) are allowed to raise to the caller.

parse_version_string
A function to turn a version string into a Version, a comparable
namedtuple:
version_tuple = microversion_parse.parse_version_string('2.1')
If the provided string is not a valid microversion string, TypeError
is raised.

extract_version
Combines get_version and parse_version_string to find and validate
a microversion for a given service type in a collection of headers:
version_tuple = microversion_parse.extract_version(
headers, # a representation of headers, as accepted by get_version
service_type, # service type identify to match in headers
versions_list, # an ordered list of strings of version numbers that
# are the valid versions presented by this service
)
latest will be translated to whatever the max version is in versions_list.
If the found version is not in versions_list a ValueError is raised.
Note that extract_version does not support legacy_headers.

MicroversionMiddleware
A WSGI middleware that can wrap an application that needs to be microversion
aware. The application will get a WSGI environ with a
‘SERVICE_TYPE.microversion’ key that has a value of the microversion found at
an ‘openstack-api-version’ header that matches SERVICE_TYPE. If no header is
found, the minimum microversion will be set. If the special keyword ‘latest’ is
used, the maximum microversion will be set.
If the requested microversion is not available a 406 response is returned.
If there is an error parsing a provided header, a 400 response is returned.
Otherwise the application is called.
The middleware is configured when it is created. Three parameters are required:

app
The next WSGI middleware or application in the stack.

service_type
The service type of the application, used to identify microversion headers.

versions_list
An ordered list of legitimate microversions (as strings) for the application.
It’s assumed that any application that is using microversions will have such
a list for its own housekeeping and documentation.

One named parameter is optional:

json_error_formatter
A Webob error formatter that can be used to structure the response when JSON
is expected.

For example:
def app():
app = middleware.MicroversionMiddleware(
MyWSGIApp(), 'cats', ['1.0', '1.1', '1.2'])
return app