case-insensitivity for header field names

[kenichi]

while testing angelo on heroku, i discovered that heroku's router is downcasing request header keys. this is valid according to:

http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2

this change should make all access to request header keys insensitive, though probably not in a very performant way.

there's most likely a way better way of handling this... but wanted to get this on the radar. this app actually works on heroku with the beta websocket support enabled. note the Gemfile.

[ungoldman]

:+1:

[tarcieri]

Note that Reel did something like this originally (actually it put headers in the canonical form instead of downcasing) but we removed it for performance reasons. See e.g. 9e0aeb2544

I know Mongrel did something like this, and perhaps that's where Heroku got the idea from, but doing this eagerly is somewhat expensive, especially for headers that are never accessed.

[kenichi]

i definitely understand the performance reasons, and i don't like the way rack upcases and prepends 'HTTP_' to everything; but, for situations like this where header keys are not actually required to be in a certain case, it doesn't work unless the case-insensitivity is there. i also don't like that heroku is doing that to the requests, but alas.

note that this does not eagerly change header keys; it should only run the block when a key is not found. so i think it's basically the difference between one more Hash being allocated by the merge, if the key is never accessed. in siege tests, it seems to drop about 150 transactions / sec.

[tarcieri]

Okay, my bad, I clearly didn't read the code. This is a neat trick, and seems ok to me, thanks!