readavailable returns 0 bytes

[tbenst]

I'm subscribing to topics on a webserver, and when I subscribe to 15 topics everything is fine, but when I subscribe to more, say 20 or 50, I start reading IO with 0 bytes. My code looks something like,

HTTP.WebSockets.open(ws_endpoint) do ws
  # [subscribe to topics by writing to ws]
  while true
    if !eof(ws)
      @info length(readavailable(ws))
    end
  end
end

And the output is something like,

[ Info: 88
[ Info: 88
[ Info: 88
[...]
[ Info: 88
[ Info: 88
[ Info: 0
[hangs]

I thought !eof should guarantee that at least 1 byte is read? I think what's happening is HTTP.WebSockets.open can't keep up with the message rate, as it's failing in 10-100K / s range, but succeeding around 1K / s (order of magnitude). However I'm not sure if this diagnosis is correct--I'm a bit at a loss for what could be going wrong.

I tried to create a MWE using a fast websocket server that ought to be able to create >10K messages / sec but got stuck on #794

versions

• Julia 1.6.1
• HTTP v0.9.17

[quinnj]

The problem in the old websockets code is that if an empty CLOSE message was received from the remote connection, this "empty message" was returned to the user instead of being thrown as an error which non-empty CLOSE messages would do.

I just merged an overhaul of the websockets code that fixes this, so HTTP#master should be correct now.