Description
While looking into the asynchttpserver example (eg #16599 + recent PR's), I noticed that activeDescriptors (and hence shouldAcceptRequest) doesn't seem to work.
Example
when true:
import asynchttpserver, strformat
import asyncdispatch
proc main {.async.} =
const port = 8080
var server = newAsyncHttpServer()
proc cb(req: Request) {.async.} =
await sleepAsync(20000) # if comment this out, will still fail if enough requests come fast enough
await req.respond(Http200, "Hello World")
server.listen(Port(port))
while true:
let num = activeDescriptors()
let ok = server.shouldAcceptRequest(assumedDescriptorsPerRequest = 1)
let maxi = maxDescriptors()
echo (ok: ok, maxi: maxi, num: num)
if ok:
await server.acceptRequest(cb)
echo "after"
else:
echo "before poll"
poll()
echo "after poll"
waitFor main()ulimit -n 13 # adjust as needed for your OS; small enough to make it easier to reproduce bug
nim r main
# in another tab:
nim r -d:nimAsyncHttpServerEnableTest -d:case3 --lib:lib $timn_D/tests/nim/all/t11653.nim
Current Output
Error: unhandled exception: Too many open files is raised after < 1 second, eg:
(ok: true, maxi: 12, num: 0)
after
(ok: true, maxi: 12, num: 1)
after
(ok: true, maxi: 12, num: 1)
after
(ok: true, maxi: 12, num: 1)
after
(ok: true, maxi: 12, num: 1)
after
(ok: true, maxi: 12, num: 1)
after
(ok: true, maxi: 12, num: 1)
after
(ok: true, maxi: 12, num: 1)
/Users/timothee/git_clone/nim/timn/tests/nim/all/t11653.nim(123) t11653
/Users/timothee/git_clone/nim/Nim_devel/lib/pure/asyncdispatch.nim(1935) waitFor
/Users/timothee/git_clone/nim/Nim_devel/lib/pure/asyncdispatch.nim(1627) poll
/Users/timothee/git_clone/nim/Nim_devel/lib/pure/asyncdispatch.nim(1368) runOnce
/Users/timothee/git_clone/nim/Nim_devel/lib/pure/asyncdispatch.nim(208) processPendingCallbacks
/Users/timothee/git_clone/nim/Nim_devel/lib/pure/asyncmacro.nim(29) acceptRequestNimAsyncContinue
/Users/timothee/git_clone/nim/Nim_devel/lib/pure/asyncmacro.nim(145) acceptRequestIter
/Users/timothee/git_clone/nim/Nim_devel/lib/pure/asyncfutures.nim(372) read
...
Expected Output
works
Additional Information
1.5.1 d2f4f25
Not sure how to fix this.
=> see RFC nim-lang/RFCs#382
notes
Using await sleepAsync(500) doesn't change anything (still crashes the server), the problem is that activeDescriptors, and hence shouldAcceptRequest , is incorrect (under-reports).
note that if you comment out await sleepAsync(20000), it'll still crash but will take more time to crash it, eg this will crash it: for i in {1..2000}; do curl localhost:8080/&; ; done
with:
(ok: true, maxi: 12, num: 3)
after
(ok: true, maxi: 12, num: 4)
after
(ok: true, maxi: 12, num: 5)
after
(ok: true, maxi: 12, num: 5)
after
(ok: true, maxi: 12, num: 6)
and then crashes
using let ok = server.shouldAcceptRequest() instead of let ok = server.shouldAcceptRequest(assumedDescriptorsPerRequest = 1) (ie, using the default 5) doesn't help