proxy_cache control via HTTP/2 trailing headers

[Claudiu]

Hi,

I'm wondering if there is a way to instruct nginx to cache or not a 
backend response based on trailing headers?

Use-case is that backend does some heavy longer running streaming work 
that in some edge cases may fail midway. As the response is already 
streaming I need to tell nginx to not cache that response as it is 
failed. Status code is already sent and I don't think I can change it 
later via trailing headers, thus, proxy_cache_valid directive seems of 
no use. However, docs mention the X-Accel-Expires header that 
technically could be sent as trailing header. What I don't know yet is 
if nginx supports X-Accel-Expires as trailing header or if it supports 
trailing headers in backend responses at all.

Or, is there another way to accomplish something like this?

-- 
Claudiu