To manage this complexity, version your API. Versioning helps us to iterate faster when the needed changes are identified in the APIs.
Change in an API is inevitable as our knowledge and experience of a system improve. Managing the impact of this change can be quite a challenge when it threatens to break existing client integration.
1. When to version?
APIs only need to be up-versioned when a breaking change is made.
Breaking changes include:
- a change in the format of the response data for one or more calls
- a change in the request or response type (i.e. changing an integer to a float)
- removing any part of the API.
Breaking changes should always result in a change to the major version number for an API or content response type.
Non-breaking changes, such as adding new endpoints or new response parameters, do not require a change to the major version number.
However, it can be helpful to track the minor versions of APIs when changes are made to support customers who may be receiving cached versions of data or might be experiencing other API issues.
2. How to version a REST API?
REST doesn’t provide for any specific versioning guidelines, but the more commonly used approaches fall into three categories:
2.1. URI Versioning
Using the URI is the most straightforward approach (and most commonly used as well) though it does violate the principle that a URI should refer to a unique resource. You are also guaranteed to break client integration when a version is updated.
The version need not be numeric, nor specified using the “v[x]” syntax.
Alternatives include dates, project names, seasons, or other identifiers that are meaningful enough to the team producing the APIs and flexible enough to change as the versions change.
2.2. Versioning using Custom Request Header
A custom header (e.g. Accept-version) allows you to preserve your URIs between versions though it is effectively a duplicate of the content negotiation behavior implemented by the existing Accept header.
Accept-version: v1 Accept-version: v2
2.3. Versioning using “Accept” header
Content negotiation may let you preserve a clean set of URLs, but you still have to deal with the complexity of serving different versions of content somewhere.
This burden tends to be moved up the stack to your API controllers which become responsible for figuring out which version of a resource to send.
The result tends to be a more complex API as clients have to know which headers to specify before requesting a resource.
Accept: application/vnd.example.v1+json Accept: application/vnd.example+json;version=1.0
In the real world, an API is never going to be completely stable. So it’s important how this change is managed.
A well-documented and gradual deprecation of API can be an acceptable practice for most APIs.
Actually Roy Fielding stated that including the version in the URL is really against REST.
Fielding: “By versioning, I meant sticking client-visible interface numbers inside various names so that the client labels every interaction as belonging to a given version of that API.
Unfortunately, versioning interface names only manages change for the API owner’s sake. That is a myopic view of interface design: one where the owner’s desire for control ignores the customer’s need for continuity.”
He doesn’t state in those sentences that including version in the URL is bad.
He states that including a version number in an *interface* name is bad. Very different.
If the URL is not an interface in the context of REST, what is?
so, instead of writing /vx/ in url we add “accepted-version=x” in the header and it is all good? How stupid. Consumer needs to know what they are calling, because if in version one you get an apple and in version two you get and orange and you want the apple, you need to know which interface to call.
How do you have a service indicate version in the response? Currently we’re using Content-Type headers. For example, with version 1.3 of a service called “customers”, we’d have something like “Content-Type: application/vnd.com.ourcompany.customers.v1-3+json”. How do you prefer to do it?
Having version numbers in media-types is perhaps the best way to implement versioning. You are already using it.
This should apply to the Requests as well not just the Responses.
The article is addressing requests. URIs and Accept headers are for requests.
Do you deploy various versions as single service Or it should be two separate services running in different pods
A third option would be to include a version key:value hint in the JSON body.
That won’t be of much use with GET.