RESTful Alternatives to DELETE Request Body

Question

While the HTTP 1.1 spec seems to allow message bodies on DELETE requests, it seems to indicate that servers should ignore it since there are no defined semantics for it.

4.3 Message Body

A server SHOULD read and forward a message-body on any request; if the request method does not include defined semantics for an entity-body, then the message-body SHOULD be ignored when handling the request.

I've already reviewed several related discussions on this topic on SO and beyond, such as:

• Is an entity body allowed for an HTTP DELETE request?
• Payloads of HTTP Request Methods
• HTTP GET with request body

Most discussions seem to concur that providing a message body on a DELETE may be allowed, but is generally not recommended.

Further, I've noticed a trend in various HTTP client libraries where more and more enhancements seem to be getting logged for these libraries to support request bodies on DELETE. Most libraries seem to oblige, although occasionally with a little bit of initial resistance.

My use case calls for the addition of some required metadata on a DELETE (e.g. the "reason" for deletion, along with some other metadata required for deletion). I've considered the following options, none of which seem completely appropriate and inline with HTTP specs and/or REST best practices:

• Message Body - The spec indicates that message bodies on DELETE have no semantic value; not fully supported by HTTP clients; not standard practice
• Custom HTTP Headers - Requiring custom headers is generally against standard practices; using them is inconsistent with the rest of my API, none of which require custom headers; further, no good HTTP response available to indicate bad custom header values (probably a separate question altogether)
• Standard HTTP Headers - No standard headers are appropriate
• Query Parameters - Adding query params actually changes the Request-URI being deleted; against standard practices
• POST Method - (e.g. POST /resourceToDelete { deletemetadata }) POST is not a semantic option for deleting; POST actually represents the opposite action desired (i.e. POST creates resource subordinates; but I need to delete the resource)
• Multiple Methods - Splitting the DELETE request into two operations (e.g. PUT delete metadata, then DELETE) splits an atomic operation into two, potentially leaving an inconsistent state. The delete reason (and other related metadata) are not part of the resource representation itself.

My first preference would probably be to use the message body, second to custom HTTP headers; however, as indicated, there are some downsides to these approaches.

Are there any recommendations or best practices inline with REST/HTTP standards for including such required metadata on DELETE requests? Are there any other alternatives that I haven't considered?

Answer 1

What you seem to want is one of two things, neither of which are a pure DELETE:

1. You have two operations, a PUT of the delete reason followed by a DELETE of the resource. Once deleted, the contents of the resource are no longer accessible to anyone. The 'reason' cannot contain a hyperlink to the deleted resource. Or,
2. You are trying to alter a resource from state=active to state=deleted by using the DELETE method. Resources with state=deleted are ignored by your main API but might still be readable to an admin or someone with database access. This is permitted - DELETE doesn't have to erase the backing data for a resource, only to remove the resource exposed at that URI.

Any operation which requires a message body on a DELETE request can be broken down into at it's most general, a POST to do all the necessary tasks with the message body, and a DELETE. I see no reason to break the semantics of HTTP.

Answer 2

Given the situation you have, I would take one of the following approaches:

• Send a PUT or PATCH: I am deducing that the delete operation is virtual, by the nature of needing a delete reason. Therefore, I believe updating the record via a PUT/PATCH operation is a valid approach, even though it is not a DELETE operation per se.
• Use the query parameters: The resource uri is not being changed. I actually think this is also a valid approach. The question you linked was talking about not allowing the delete if the query parameter was missing. In your case, I would just have a default reason if the reason is not specified in the query string. The resource will still be resource/:id. You can make it discoverable with Link headers on the resource for each reason (with a rel tag on each to identify the reason).
• Use a separate endpoint per reason: Using a url like resource/:id/canceled. This does actually change the Request-URI and is definitely not RESTful. Again, link headers can make this discoverable.

Remember that REST is not law or dogma. Think of it more as guidance. So, when it makes sense to not follow the guidance for your problem domain, don't. Just make sure your API consumers are informed of the variance.

Answer 3

Despite some recommendations not to use the message body for DELETE requests, this approach may be appropriate in certain use cases. This is the approach we ended up using after evaluating the other options mentioned in the question/answers, and after collaborating with consumers of the service.

While the use of the message body is not ideal, none of the other options were perfectly fitting either. The request body DELETE allowed us to easily and clearly add semantics around additional data/metadata that was needed to accompany the DELETE operation.

I'd still be open to other thoughts and discussions, but wanted to close the loop on this question. I appreciate everyone's thoughts and discussions on this topic!

Answer 4

I suggest you include the required metadata as part of the URI hierarchy itself. An example (Naive):

If you need to delete entries based on a date range, instead of passing the start date and end date in body or as query parameters, structure the URI such a way that you pass the required information as part of the URI.

e.g.

DELETE /entries/range/01012012/31122012 -- Delete all entries between 01 January 2012 to 31st December 2012

Hope this helps.