Write FD not non-blocking in async echo server

[paurkedal]

Posting a large file though examples/async_echo_post.ml from the current master gives me the following error:

eof                    
2018-06-21 09:09:51.020525+02:00 Error (monitor.ml.Error
  (Unix.Unix_error "Invalid argument" writev_assume_fd_is_nonblocking "")
  ("Raised at file \"src/import0.ml\" (inlined), line 351, characters 22-32"
    "Called from file \"src/result.ml\" (inlined), line 168, characters 17-26"
    "Called from file \"src/raw_fd.ml\", line 272, characters 4-60"
    "Called from file \"src/raw_fd.ml\", line 265, characters 10-26"
    "Re-raised at file \"async/faraday_async.ml\", line 52, characters 6-15"
    "Called from file \"async/httpaf_async.ml\", line 132, characters 10-23"
    "Called from file \"lib/body.ml\", line 115, characters 4-28"
    "Called from file \"lib/parse.ml\" (inlined), line 137, characters 2-26"
    "Called from file \"lib/parse.ml\", line 168, characters 18-31"
    "Called from file \"lib/parser.ml\", line 53, characters 38-43"
    "Called from file \"lib/parse.ml\", line 301, characters 19-53"
    "Called from file \"lib/server_connection.ml\", line 244, characters 17-50"
    "Called from file \"async/httpaf_async.ml\", line 38, characters 12-44"
    "Called from file \"async/httpaf_async.ml\", line 113, characters 14-127"
    "Called from file \"src/job_queue.ml\", line 159, characters 6-47"
    "Caught by monitor (id 6)"))
^C

As you can see it issues eof, but there is no data returned

curl --data-binary @/boot/initrd.img-4.15.0-23-generic http://localhost:8080 | wc
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 55.6M    0     0  100 55.6M      0  36.5M  0:00:01  0:00:01 --:--:-- 36.5M
curl: (52) Empty reply from server
      0       0       0

This is built from the current master against faraday 0.5.1 and async v0.11.0, though I also got the same with faraday pinned to bd1a9321 (the lwt PR).

[seliopou]

If this is indeed caused by writev returning EINVAL that's caused by the iovec arguments rather than the file descriptor.

[seliopou]

Or it's that the FD is closed. Which is probably what's happening.