Using REST Update Notification Hub to add APNS certs fails with 409

Question

Hi - I'm trying to use the Update Notification Hub REST call (https://msdn.microsoft.com/en-us/library/azure/dn223260.aspx) to add a valid APNS cert to an existing hub. When I do this, the update fails with a response code of 409 - which is not mentioned
in the possible codes on that documentation page... Seems to be complaining that hub already exists.
When I use the Create Notification Hub REST Call (https://msdn.microsoft.com/en-us/library/azure/dn223269.aspx) and include the proper <ApnsCredential> element it succeeds.
I see no difference in the docs between the two calls.  The request body is described slightly differently. It appears to me that create and update are the same call? What causes a 409 when calling the Update method?
How am I supposed to update the push certs of an existing hub?
Thanks!

Answer 1

The answer is that the HTTP spec implies that for REST style calls for updating a resource at the same URI - you need to include the "If-Match" header set to '*'
see: https://msdn.microsoft.com/en-us/library/dd541480.aspx
and section 14.24 of RFC2616 ( http://www.rfc-editor.org/rfc/rfc2616.txt )
In my opinion this is a documentation bug - the Request Headers section of Update Hub ( https://msdn.microsoft.com/en-us/library/azure/dn223260.aspx ) should mention it requires the "If-Match" header.  It is required because without it
- this becomes a Create Hub call