Hi Stephen,
On 21/08/15 04:57, Stephen Halter wrote:
Hi,
I've been following a guide explaining how to send TCP sockets over
pipes found
at
https://nikhilm.github.io/uvbook/processes.html#sending-file-descriptors-over-pipes.
I've noticed on mac and linux that if I send a 1 byte "dummy_buf" using
uv_write2 and I return a 1 byte buffer from the workers' alloc_buffer
callback, the workers' on_new_connection callback will sometimes be
called with nread == 0. In these circumstances (and only these
circumstances in my testing at least) uv_pipe_pending_count will return
0. On windows nread is never zero and uv_pipe_pending_count never
returns zero.
Do you get the alloc / read callbacks called again in the future, this
time with the handle?
I've also noticed if I return a 2 byte buffer from the alloc_buffer
callback, I never see nread == 0 or uv_pipe_pending_count return 0 even
on mac and linux. Sadly, having the alloc_buffer callback return a
larger than necessary buffer causes an issue on windows where part of
the *next* ipc frame to be read into the to returned buffer under high
load. This, of course, turns into complete disaster where the following
assertion
fails:
https://github.com/libuv/libuv/blob/2a51b61e460b43b6813425c239db1e5db6931fc9/src/win/pipe.c#L1633
and the pipe rendered unusable.
This windows thing sounds like a bug.
This can all be worked around by simply using the same sized buffers on
both the sending and receiving side and then accepting that
nread/uv_pipe_pending_count will sometimes equal zero on mac/linux in
which case I just immediately exit the callback. I just want to make
sure this is the expected behavior, and that this is the right thing to do.
If this isn't expected, I'm happy to file an issue.
Please do open an issue, and attach any test code you can provide, so
it's easier for us to debug.
Thanks!
--
Saúl Ibarra Corretgé
http://bettercallsaghul.com
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