Add the docs for API Microversion
Change-Id: I1a08f3ca46c79a96a21bb62f3723bf7c390f9f35
This commit is contained in:
parent
31fbbff91f
commit
2ab2ced6c4
doc/source
zun/api
1
doc/source/api_microversion_history.rst
Normal file
1
doc/source/api_microversion_history.rst
Normal file
@ -0,0 +1 @@
|
|||||||
|
.. include:: ../../zun/api/rest_api_version_history.rst
|
319
doc/source/dev/api_microversion.rst
Normal file
319
doc/source/dev/api_microversion.rst
Normal file
@ -0,0 +1,319 @@
|
|||||||
|
API Microversions
|
||||||
|
=================
|
||||||
|
|
||||||
|
Background
|
||||||
|
----------
|
||||||
|
|
||||||
|
Zun uses a framework we call 'API Microversions' for allowing changes
|
||||||
|
to the API while preserving backward compatibility. The basic idea is
|
||||||
|
that a user has to explicitly ask for their request to be treated with
|
||||||
|
a particular version of the API. So breaking changes can be added to
|
||||||
|
the API without breaking users who don't specifically ask for it. This
|
||||||
|
is done with an HTTP header ``OpenStack-API-Version`` which has as its
|
||||||
|
value a string containing the name of the service, ``container``, and a
|
||||||
|
monotonically increasing semantic version number starting from ``1.1``.
|
||||||
|
The full form of the header takes the form::
|
||||||
|
|
||||||
|
OpenStack-API-Version: container 1.1
|
||||||
|
|
||||||
|
If a user makes a request without specifying a version, they will get
|
||||||
|
the ``BASE_VER`` as defined in
|
||||||
|
``zun/api/controllers/versions.py``. This value is currently ``1.1`` and
|
||||||
|
is expected to remain so for quite a long time.
|
||||||
|
|
||||||
|
|
||||||
|
When do I need a new Microversion?
|
||||||
|
----------------------------------
|
||||||
|
|
||||||
|
A microversion is needed when the contract to the user is
|
||||||
|
changed. The user contract covers many kinds of information such as:
|
||||||
|
|
||||||
|
- the Request
|
||||||
|
|
||||||
|
- the list of resource urls which exist on the server
|
||||||
|
|
||||||
|
Example: adding a new container/{ID}/foo which didn't exist in a
|
||||||
|
previous version of the code
|
||||||
|
|
||||||
|
- the list of query parameters that are valid on urls
|
||||||
|
|
||||||
|
Example: adding a new parameter ``is_yellow`` container/{ID}?is_yellow=True
|
||||||
|
|
||||||
|
- the list of query parameter values for non free form fields
|
||||||
|
|
||||||
|
Example: parameter filter_by takes a small set of constants/enums "A",
|
||||||
|
"B", "C". Adding support for new enum "D".
|
||||||
|
|
||||||
|
- new headers accepted on a request
|
||||||
|
|
||||||
|
- the list of attributes and data structures accepted.
|
||||||
|
|
||||||
|
Example: adding a new attribute 'locked': True/False to the request body
|
||||||
|
|
||||||
|
|
||||||
|
- the Response
|
||||||
|
|
||||||
|
- the list of attributes and data structures returned
|
||||||
|
|
||||||
|
Example: adding a new attribute 'locked': True/False to the output
|
||||||
|
of container/{ID}
|
||||||
|
|
||||||
|
- the allowed values of non free form fields
|
||||||
|
|
||||||
|
Example: adding a new allowed ``status`` to container/{ID}
|
||||||
|
|
||||||
|
- the list of status codes allowed for a particular request
|
||||||
|
|
||||||
|
Example: an API previously could return 200, 400, 403, 404 and the
|
||||||
|
change would make the API now also be allowed to return 409.
|
||||||
|
|
||||||
|
See [#f2]_ for the 400, 403, 404 and 415 cases.
|
||||||
|
|
||||||
|
- changing a status code on a particular response
|
||||||
|
|
||||||
|
Example: changing the return code of an API from 501 to 400.
|
||||||
|
|
||||||
|
.. note:: Fixing a bug so that a 400+ code is returned rather than a 500 or
|
||||||
|
503 does not require a microversion change. It's assumed that clients are
|
||||||
|
not expected to handle a 500 or 503 response and therefore should not
|
||||||
|
need to opt-in to microversion changes that fixes a 500 or 503 response
|
||||||
|
from happening.
|
||||||
|
According to the OpenStack API Working Group, a
|
||||||
|
**500 Internal Server Error** should **not** be returned to the user for
|
||||||
|
failures due to user error that can be fixed by changing the request on
|
||||||
|
the client side. See [#f1]_.
|
||||||
|
|
||||||
|
- new headers returned on a response
|
||||||
|
|
||||||
|
The following flow chart attempts to walk through the process of "do
|
||||||
|
we need a microversion".
|
||||||
|
|
||||||
|
|
||||||
|
.. graphviz::
|
||||||
|
|
||||||
|
digraph states {
|
||||||
|
|
||||||
|
label="Do I need a microversion?"
|
||||||
|
|
||||||
|
silent_fail[shape="diamond", style="", group=g1, label="Did we silently
|
||||||
|
fail to do what is asked?"];
|
||||||
|
ret_500[shape="diamond", style="", group=g1, label="Did we return a 500
|
||||||
|
before?"];
|
||||||
|
new_error[shape="diamond", style="", group=g1, label="Are we changing what
|
||||||
|
status code is returned?"];
|
||||||
|
new_attr[shape="diamond", style="", group=g1, label="Did we add or remove an
|
||||||
|
attribute to a payload?"];
|
||||||
|
new_param[shape="diamond", style="", group=g1, label="Did we add or remove
|
||||||
|
an accepted query string parameter or value?"];
|
||||||
|
new_resource[shape="diamond", style="", group=g1, label="Did we add or remove a
|
||||||
|
resource url?"];
|
||||||
|
|
||||||
|
|
||||||
|
no[shape="box", style=rounded, label="No microversion needed"];
|
||||||
|
yes[shape="box", style=rounded, label="Yes, you need a microversion"];
|
||||||
|
no2[shape="box", style=rounded, label="No microversion needed, it's
|
||||||
|
a bug"];
|
||||||
|
|
||||||
|
silent_fail -> ret_500[label=" no"];
|
||||||
|
silent_fail -> no2[label="yes"];
|
||||||
|
|
||||||
|
ret_500 -> no2[label="yes [1]"];
|
||||||
|
ret_500 -> new_error[label=" no"];
|
||||||
|
|
||||||
|
new_error -> new_attr[label=" no"];
|
||||||
|
new_error -> yes[label="yes"];
|
||||||
|
|
||||||
|
new_attr -> new_param[label=" no"];
|
||||||
|
new_attr -> yes[label="yes"];
|
||||||
|
|
||||||
|
new_param -> new_resource[label=" no"];
|
||||||
|
new_param -> yes[label="yes"];
|
||||||
|
|
||||||
|
new_resource -> no[label=" no"];
|
||||||
|
new_resource -> yes[label="yes"];
|
||||||
|
|
||||||
|
{rank=same; yes new_attr}
|
||||||
|
{rank=same; no2 ret_500}
|
||||||
|
{rank=min; silent_fail}
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
**Footnotes**
|
||||||
|
|
||||||
|
.. [#f1] When fixing 500 errors that previously caused stack traces, try
|
||||||
|
to map the new error into the existing set of errors that API call
|
||||||
|
could previously return (400 if nothing else is appropriate). Changing
|
||||||
|
the set of allowed status codes from a request is changing the
|
||||||
|
contract, and should be part of a microversion (except in [#f2]_).
|
||||||
|
|
||||||
|
The reason why we are so strict on contract is that we'd like
|
||||||
|
application writers to be able to know, for sure, what the contract is
|
||||||
|
at every microversion in Zun. If they do not, they will need to write
|
||||||
|
conditional code in their application to handle ambiguities.
|
||||||
|
|
||||||
|
When in doubt, consider application authors. If it would work with no
|
||||||
|
client side changes on both Zun versions, you probably don't need a
|
||||||
|
microversion. If, on the other hand, there is any ambiguity, a
|
||||||
|
microversion is probably needed.
|
||||||
|
|
||||||
|
.. [#f2] The exception to not needing a microversion when returning a
|
||||||
|
previously unspecified error code is the 400, 403, 404 and 415 cases. This is
|
||||||
|
considered OK to return even if previously unspecified in the code since
|
||||||
|
it's implied given keystone authentication can fail with a 403 and API
|
||||||
|
validation can fail with a 400 for invalid JSON request body. Request to
|
||||||
|
url/resource that does not exist always fails with 404. Invalid content types
|
||||||
|
are handled before API methods are called which results in a 415.
|
||||||
|
|
||||||
|
.. note:: When in doubt about whether or not a microversion is required
|
||||||
|
for changing an error response code, consult the `Zun Team`_.
|
||||||
|
|
||||||
|
.. _Zun Team: https://wiki.openstack.org/wiki/Zun
|
||||||
|
|
||||||
|
|
||||||
|
When a microversion is not needed
|
||||||
|
---------------------------------
|
||||||
|
|
||||||
|
A microversion is not needed in the following situation:
|
||||||
|
|
||||||
|
- the response
|
||||||
|
|
||||||
|
- Changing the error message without changing the response code
|
||||||
|
does not require a new microversion.
|
||||||
|
|
||||||
|
- Removing an inapplicable HTTP header, for example, suppose the Retry-After
|
||||||
|
HTTP header is being returned with a 4xx code. This header should only be
|
||||||
|
returned with a 503 or 3xx response, so it may be removed without bumping
|
||||||
|
the microversion.
|
||||||
|
|
||||||
|
In Code
|
||||||
|
-------
|
||||||
|
|
||||||
|
In ``zun/api/controllers/base.py`` we define an ``@api_version`` decorator
|
||||||
|
which is intended to be used on top-level Controller methods. It is
|
||||||
|
not appropriate for lower-level methods. Some examples:
|
||||||
|
|
||||||
|
Adding a new API method
|
||||||
|
~~~~~~~~~~~~~~~~~~~~~~~
|
||||||
|
|
||||||
|
In the controller class::
|
||||||
|
|
||||||
|
@base.Controller.api_version("1.2")
|
||||||
|
def my_api_method(self, req, id):
|
||||||
|
....
|
||||||
|
|
||||||
|
This method would only be available if the caller had specified an
|
||||||
|
``OpenStack-API-Version`` of >= ``1.2``. If they had specified a
|
||||||
|
lower version (or not specified it and received the default of ``1.1``)
|
||||||
|
the server would respond with ``HTTP/406``.
|
||||||
|
|
||||||
|
Removing an API method
|
||||||
|
~~~~~~~~~~~~~~~~~~~~~~
|
||||||
|
|
||||||
|
In the controller class::
|
||||||
|
|
||||||
|
@base.Controller.api_version("1.2", "1.3")
|
||||||
|
def my_api_method(self, req, id):
|
||||||
|
....
|
||||||
|
|
||||||
|
This method would only be available if the caller had specified an
|
||||||
|
``OpenStack-API-Version`` of >= ``1.2`` and
|
||||||
|
``OpenStack-API-Version`` of <= ``1.3``. If ``1.4`` or later
|
||||||
|
is specified the server will respond with ``HTTP/406``.
|
||||||
|
|
||||||
|
Changing a method's behavior
|
||||||
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||||
|
|
||||||
|
In the controller class::
|
||||||
|
|
||||||
|
@base.Controller.api_version("1.2", "1.3")
|
||||||
|
def my_api_method(self, req, id):
|
||||||
|
.... method_1 ...
|
||||||
|
|
||||||
|
@base.Controller.api_version("1.4") #noqa
|
||||||
|
def my_api_method(self, req, id):
|
||||||
|
.... method_2 ...
|
||||||
|
|
||||||
|
If a caller specified ``1.2``, ``1.3`` (or received the default
|
||||||
|
of ``1.1``) they would see the result from ``method_1``,
|
||||||
|
and for ``1.4`` or later they would see the result from ``method_2``.
|
||||||
|
|
||||||
|
It is vital that the two methods have the same name, so the second of
|
||||||
|
them will need ``# noqa`` to avoid failing flake8's ``F811`` rule. The
|
||||||
|
two methods may be different in any kind of semantics (schema
|
||||||
|
validation, return values, response codes, etc)
|
||||||
|
|
||||||
|
When not using decorators
|
||||||
|
~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||||
|
|
||||||
|
When you don't want to use the ``@api_version`` decorator on a method
|
||||||
|
or you want to change behavior within a method (say it leads to
|
||||||
|
simpler or simply a lot less code) you can directly test for the
|
||||||
|
requested version with a method as long as you have access to the api
|
||||||
|
request object (commonly accessed with ``pecan.request``). Every API
|
||||||
|
method has an versions object attached to the request object and that
|
||||||
|
can be used to modify behavior based on its value::
|
||||||
|
|
||||||
|
def index(self):
|
||||||
|
<common code>
|
||||||
|
|
||||||
|
req_version = pecan.request.headers.get(Version.string)
|
||||||
|
req1_min = versions.Version("1.1")
|
||||||
|
req1_max = versions.Version("1.5")
|
||||||
|
req2_min = versions.Version("1.6")
|
||||||
|
req2_max = versions.Version("1.10")
|
||||||
|
|
||||||
|
if req_version.matches(req1_min, req1_max):
|
||||||
|
....stuff....
|
||||||
|
elif req_version.matches(req2min, req2_max):
|
||||||
|
....other stuff....
|
||||||
|
elif req_version > versions.Version("1.10"):
|
||||||
|
....more stuff.....
|
||||||
|
|
||||||
|
<common code>
|
||||||
|
|
||||||
|
The first argument to the matches method is the minimum acceptable version
|
||||||
|
and the second is maximum acceptable version. If the specified minimum
|
||||||
|
version and maximum version are null then ``ValueError`` is returned.
|
||||||
|
|
||||||
|
Other necessary changes
|
||||||
|
-----------------------
|
||||||
|
|
||||||
|
If you are adding a patch which adds a new microversion, it is
|
||||||
|
necessary to add changes to other places which describe your change:
|
||||||
|
|
||||||
|
* Update ``REST_API_VERSION_HISTORY`` in
|
||||||
|
``zun/api/controllers/versions.py``
|
||||||
|
|
||||||
|
* Update ``CURRENT_MAX_VER`` in
|
||||||
|
``zun/api/controllers/versions.py``
|
||||||
|
|
||||||
|
* Add a verbose description to
|
||||||
|
``zun/api/rest_api_version_history.rst``. There should
|
||||||
|
be enough information that it could be used by the docs team for
|
||||||
|
release notes.
|
||||||
|
|
||||||
|
* Update the expected versions in affected tests, for example in
|
||||||
|
``zun/tests/unit/api/controllers/test_base.py``.
|
||||||
|
|
||||||
|
* Make a new commit to python-zunclient and update corresponding
|
||||||
|
files to enable the newly added microversion API.
|
||||||
|
|
||||||
|
* If the microversion changes the response schema, a new schema and test for
|
||||||
|
the microversion must be added to Tempest.
|
||||||
|
|
||||||
|
Allocating a microversion
|
||||||
|
-------------------------
|
||||||
|
|
||||||
|
If you are adding a patch which adds a new microversion, it is
|
||||||
|
necessary to allocate the next microversion number. Except under
|
||||||
|
extremely unusual circumstances and this would have been mentioned in
|
||||||
|
the zun spec for the change, the minor number of ``CURRENT_MAX_VER``
|
||||||
|
will be incremented. This will also be the new microversion number for
|
||||||
|
the API change.
|
||||||
|
|
||||||
|
It is possible that multiple microversion patches would be proposed in
|
||||||
|
parallel and the microversions would conflict between patches. This
|
||||||
|
will cause a merge conflict. We don't reserve a microversion for each
|
||||||
|
patch in advance as we don't know the final merge order. Developers
|
||||||
|
may need over time to rebase their patch calculating a new version
|
||||||
|
number as above based on the updated value of ``CURRENT_MAX_VER``.
|
@ -27,6 +27,15 @@ from zun.common.i18n import _
|
|||||||
#
|
#
|
||||||
# Add details of new api versions here:
|
# Add details of new api versions here:
|
||||||
|
|
||||||
|
#
|
||||||
|
# For each newly added microversion change, update the API version history
|
||||||
|
# string below with a one or two line description. Also update
|
||||||
|
# rest_api_version_history.rst for extra information on microversion.
|
||||||
|
REST_API_VERSION_HISTORY = """REST API Version History:
|
||||||
|
|
||||||
|
* 1.1 - Initial version
|
||||||
|
"""
|
||||||
|
|
||||||
BASE_VER = '1.1'
|
BASE_VER = '1.1'
|
||||||
CURRENT_MAX_VER = '1.1'
|
CURRENT_MAX_VER = '1.1'
|
||||||
|
|
||||||
|
23
zun/api/rest_api_version_history.rst
Normal file
23
zun/api/rest_api_version_history.rst
Normal file
@ -0,0 +1,23 @@
|
|||||||
|
REST API Version History
|
||||||
|
========================
|
||||||
|
|
||||||
|
This documents the changes made to the REST API with every
|
||||||
|
microversion change. The description for each version should be a
|
||||||
|
verbose one which has enough information to be suitable for use in
|
||||||
|
user documentation.
|
||||||
|
|
||||||
|
1.1
|
||||||
|
---
|
||||||
|
|
||||||
|
This is the initial version of the v1.1 API which supports
|
||||||
|
microversions. The v1.1 API is from the REST API users's point of
|
||||||
|
view exactly the same as v1.0 except with strong input validation.
|
||||||
|
|
||||||
|
A user can specify a header in the API request::
|
||||||
|
|
||||||
|
OpenStack-API-Version: <version>
|
||||||
|
|
||||||
|
where ``<version>`` is any valid api version for this API.
|
||||||
|
|
||||||
|
If no version is specified then the API will behave as if a version
|
||||||
|
request of v1.1 was requested.
|
Loading…
x
Reference in New Issue
Block a user