Co-authored by Ben Willis (bwillis) and Jim Jones (aantix).
Version Cake is an unobtrusive way to version APIs in your Rails app.
app/views/posts/ - index.xml.v1.builder - index.xml.v3.builder - index.json.v1.jbuilder - index.json.v4.jbuilder
Check out https://github.com/bwillis/350-rest-api-versioning for a comparison of traditional versioning approaches and a versioncake implementation.
gem install versioncake
rails g versioncake:install
The default accept header was changed from 'X-API-Version' to 'API-Version'. If you require the 'X-' or some other variant, you can specify a custom strategy as outlined in Extraction Strategy section below.
Configuration is now done with an initializer-you can generate a default one with rails g versioncake:install and then modify the generated file to match your configuration.
The configuration options for Version Cake have changed:
Old Name New Name config.versioncake.supported_version_numbers config.resources config.versioncake.default_version config.missing_versionThe major breaking change to require a bump to v2.0 was the order of the extensions. To avoid priority issues with the format (#14), the version number and the format have been swapped.
index.v1.json.jbuilder -> index.json.v1.jbuilder
To make it easier to upgrade, run the following command to automatically rename these files:
versioncake migrate or versioncake migrate path/to/views
The configuration options for Version Cake have been namespaced and slightly renamed. The following is a mapping of the old names to the new names:
Old Name New Name config.view_versions config.versioncake.supported_version_numbers config.view_version_extraction_strategy config.versioncake.extraction_strategy config.view_version_string config.versioncake.version_key config.default_version config.versioncake.default_versionIn this simple example we will outline the code that is introduced to support a change in a version.
VersionCake.setup do |config|
config.resources do |r|
r.resource %r{.*}, [], [], (1..4)
end
config.extraction_strategy = :query_parameter # for simplicity
config.missing_version = 4
end
Often times with APIs, depending upon the version, different logic needs to be applied. With the following controller code, the initial value of @posts includes all Post entries. But if the requested API version is three or greater, we're going to eagerly load the associated comments as well.
Being able to control the logic based on the api version allow you to ensure forwards and backwards compatibility for future changes.
class PostsController < ApplicationController
def index
# shared code for all versions
@posts = Post.scoped
# version 3 or greated supports embedding post comments
if request_version >= 3
@posts = @posts.includes(:comments)
end
end
end
See the view samples below. The basic top level posts are referenced in views/posts/index.json.v1.jbuilder. But for views/posts/index.json.v4.jbuilder, we utilize the additional related comments.
Notice the version numbers are denoted by the "v{version number}" extension within the file name.
views/posts/index.json.v1.jbuilderjson.array!(@posts) do |post|
json.(post, :id, :title)
end views/posts/index.json.v4.jbuilder
json.array!(@posts) do |post|
json.(post, :id, :title)
json.comments post.comments, :id, :text
end
When a version is specified for which a view doesn't exist, the request degrades and renders the next lowest version number to ensure the API's backwards compatibility. In the following case, since views/posts/index.json.v3.jbuilder doesn't exist, views/posts/index.json.v1.jbuilder is rendered instead.
[
{
id: 1
title: "Version Cake v0.1.0 Released!"
name: "Ben"
updated_at: "2012-09-17T16:23:45Z"
},
{
id: 2
title: "Version Cake v0.2.0 Released!"
name: "Jim"
updated_at: "2012-09-17T16:23:32Z"
}
]
For a given request, if we specify the version number, and that version of the view exists, that version specific view version will be rendered. In the below case, views/posts/index.json.v1.jbuilder is rendered.
[
{
id: 1
title: "Version Cake v0.1.0 Released!"
name: "Ben"
updated_at: "2012-09-17T16:23:45Z"
},
{
id: 2
title: "Version Cake v0.2.0 Released!"
name: "Jim"
updated_at: "2012-09-17T16:23:32Z"
}
]
When no version is specified, the configured missing_version will be used to render a view. In this case, views/posts/index.json.v4.jbuilder.
[
{
id: 1
title: "Version Cake v0.1.0 Released!"
name: "Ben"
updated_at: "2012-09-17T16:23:45Z"
comments: [
{
id: 1
text: "Woah interesting approach on versioning"
}
]
},
{
id: 2
title: "Version Cake v0.2.0 Released!"
name: "Jim"
updated_at: "2012-09-17T16:23:32Z"
comments: [
{
id: 4
text: "These new features are greeeeat!"
}
]
}
]
The configuration lives in config/initializers/versioncake.rb.
Each individual resource uri can be identified by a regular expression. For each one it can be customized to have obsolete, deprecated, supported versions.
config.resources do |r|
# r.resource uri_regex, obsolete, deprecated, supported
# version 2 and 3 are still supported on users resource
r.resource %r{/users}, [1], [2,3], [4]
# all other resources only allow v4
r.resource %r{.*}, [1,2,3], [], [4]
end
You can also define the way to extract the version. The extraction_strategy allows you to set one of the default strategies or provide a proc to set your own. You can also pass it a prioritized array of the strategies.
config.extraction_strategy = :query_parameter # [:http_header, :http_accept_parameter]
These are the available strategies:
Strategy Description Example :query_parameter version in the url query parameter, for testing or to override for special casehttp://localhost:3000/posts.json?api_version=1 (This is the default.) :path_parameter version in the url path parameter api/v:api_version/ :request_parameter version that is sent in the body of the request Good for testing. :http_header Api version HTTP header API-Version: 1 :http_accept_parameter HTTP Accept header Accept: application/xml; api_version=1 why do this? custom takes the request object and must return an integer lambda {|request| request.headers["HTTP_X_MY_VERSION"].to_i } or class ExtractorStrategy; def execute(request);end;end
If you use the path_parameter strategy with resources routes, you will want to setup your routes.rb config file to capture the api version. You can do that in a few ways. If you have just a few api routes you might specify the path directly like this:
resources :cakes, path: '/api/v:api_version/cakes'
If you are using a lot of routes it might be better to keep them all inside a scope like this:
scope '/api/v:api_version' do
resources :cakes
end
When no version is supplied by a client, the version rendered will be the latest version by default. If you want to override this to another version, set the following property:
config.missing_version = 4
The extraction strategies use a default string key of api_version, but that can be changed:
config.version_key = "special_version_parameter_name"
If you do not wish to use the magic mapping of the version number to templates it can be disabled:
config.rails_view_versioning = false
If a client requests a specific version (or does not) and a version applies to the resource you can configure it to be in the response. Use the following configuration:
config.response_strategy = [:http_content_type, :http_header]
When a client makes a request to your controller the latest version of the view will be rendered. The latest version is determined by naming the template or partial with a version number that you configured to support.
- app/views/posts
- index.html.erb
- edit.html.erb
- show.html.erb
- show.json.jbuilder
- show.json.v1.jbuilder
- show.json.v2.jbuilder
- new.html.erb
- _form.html.erb
If you start supporting a newer version, v3 for instance, you do not have to copy posts/show.v2 to posts/show.v3. By default, the request for v3 or higher will gracefully degrade to the view that is the newest, supported version, in this case posts/show.v2.
You don't need to do anything special in your controller, but if you find that you want to perform some tasks for a specific version you can use request_version and version_context.resource.latest_version. This may be updated in the near future.
def index
# shared code for all versions
@posts = Post.scoped
# version 3 or greated supports embedding post comments
if request_version >= 3
@posts = @posts.includes(:comments)
end
end
When a client makes a request it will automatically receive the latest supported version of the view. The client can also request for a specific version by one of the strategies configured by view_version_extraction_strategy.
These are the types of exceptions VersionCake will raise:
Exception type Description VersionCake::UnsupportedVersionError The version is invalid, too high or too low for the resource. VersionCake::ObsoleteVersionError The version is obsolete for the resource. VersionCake::MissingVersionError If noconfig.missing_version is specified, this will be raised when no version is in the request.
Handling exceptions can simply be done by using Rails rescue_from to return app specific messages to the client.
class ApplicationController < ActionController::Base
...
rescue_from VersionCake::UnsupportedVersionError, :with => :render_unsupported_version
private
def render_unsupported_version
headers['API-Version-Supported'] = 'false'
respond_to do |format|
format.json { render json: {message: "You requested an unsupported version (#{request_version})"}, status: :unprocessable_entity }
end
end
...
end
Testing can be painful but here are some easy ways to test different versions of your api using version cake.
Allowing more extraction strategies during testing can be helpful when needing to override the version.
# config/environments/test.rb config.extraction_strategy = [:query_parameter, :request_parameter, :http_header, :http_accept_parameter]Testing a specific version
One way to test a specific version for would be to stub the requested version in the before block:
before do @controller.stubs(:request_version).returns(3) end
You can also test a specific version through a specific strategy such query_parameter or request_parameter strategies (configured in test environment) like so:
# test/integration/renders_integration_test.rb#L47
test "render version 1 of the partial based on the parameter _api_version" do
get renders_path("api_version" => "1")
assert_equal "index.html.v1.erb", @response.body
end Testing all supported versions
You can iterate over all of the supported version numbers by accessing the VersionCake.config.versioned_resources.first.available_versions.
VersionCake.config.versioned_resources.first.available_versions.each do |supported_version|
before do
@controller.stubs(:request_version).returns(supported_version)
end
test "all versions render the correct template" do
get :index
assert_equal @response.body, "index.html.v1.erb"
end
end
Thanks to all those who have helped make Version Cake really sweet:
If you think you have a security vulnerability, please submit the issue and the details to https://hackerone.com/versioncake
Create a bug/enhancement/question on github or contact aantix or bwillis through github.
Version Cake is released under the MIT license: www.opensource.org/licenses/MIT
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