Blocks network if writing to child stdin blocks

[lspitzner]

With createProcess, afaict, input events end up being performEvented directly. If the child process is busy and does not consume input in time, writing to its stdin handle may block. That happens in

https://github.com/reflex-frp/reflex-process/blob/develop/src/Reflex/Process.hs#L138

and

https://github.com/reflex-frp/reflex-process/blob/develop/src/Reflex/Process.hs#L81-L82

with no forkIO in sight. This most likely blocks the network entirely.

Desired behaviour:

• Do not block network in parent because child is slow
• Keep messages in proper order (this rules out a plain forkIO to send the messages. Even if hPutStr was threadsafe)

[3noch]

Thanks for the report!

We need to fork a single writing thread as soon as the process is forked. Then the event would write to some sort of channel which is consumed by the writer. This suffers from unbounded memory, however.

[3noch]

We may not be able to get to this for a while; feel free to beat us to it!

[3noch]

Fixed by #11