1) A way of finding how long a response took to generate. 2) A way of finding out when exceptions happen.
Can either of these be achieved with middleware, or Response transformers? I thought the timing one could probably be done by consuming all the Response output, and then as a final action at the end writing to an MVar or a Chan, which some other thread could read from to see the time elapsed. Is that possible? It seems feasible...
Are you talking about timing how long it takes to *generate* a response, or how long it takes to *send* a response? The latter would require changes to Warp which I do not want to make for the moment.
I want the generation time, but would accept send time as a rough approximation.
The former would require forcing evaluation of your response body, which will kill any lazy IO advantages you have. However, it should be implementable at the application/middleware level.
I wondered if it was possible to do so keeping the lazy IO, but if not it's not the end of the world.
See the other email I just sent; I added a function runOnException. However, I think runEx is a nicer name, so I'm going to steal it. As for the requested type signature (including a Request): it's not really feasible at the Warp level: the exceptions Warp will be catching are not necessarily part of a request, it could be in the middle of receiving a request, a timeout in between one response and the next request, etc.
Fair enough. Generally, just not losing exceptions will be appreciated - I don't expect exceptions to be common at all. Thanks, Neil