[erlang-questions] gen_tcp send blocks gen_tcp recv.

Satyam Shekhar satyamshekhar@REDACTED
Tue Sep 4 09:45:23 CEST 2012

@erik: I wasn't sure if this was the standard practice. Also, this
complicates the architecture. Now, I ll have 2 processes, that manage a tcp
socket. One for receiving and one for sending, both having reference to the
same socket. Is this ok?

@arun: The article on trapexit only show how to do async accept. It doesnt
do async send of gen_tcp socket.
To elaborate on the problem - I have one process that is an abstraction
over the gen_tcp socket. It does xml parsing on the data received on the
tcp socket and forwards parsed data to the controlling process. Also it
receives the xml from a process and sends it on the tcp socket. Lets call
this smart socket. Now, if the process that sends data to  smart socket,
sends too much of it, smart socket starts to starts blocking on send calls.

How do people usually handle such scenarios?

On Mon, Sep 3, 2012 at 9:01 PM, Arun Muralidharan <arun11299@REDACTED>wrote:

> Can you be more specific on how your sending process is overloading your
> receiving process(P1) by making a "blocking" call ? I didnt quite get it.
> Why dont you try an async design pattern as shown in
> http://www.trapexit.org/Building_a_Non-blocking_TCP_server_using_OTP_principles
> -Arun
> On Mon, Sep 3, 2012 at 12:47 PM, Erik Søe Sørensen <eriksoe@REDACTED>wrote:
>> Have you considered having one process for sending and one for receiving
>> (on the same socket)?
>> Den 03/09/2012 06.47 skrev "Satyam Shekhar" <satyamshekhar@REDACTED>:
>>>  Hi,
>>> I know this question has been asked many times.
>>> http://erlang.2086793.n4.nabble.com/Non-blocking-sends-in-gen-tcp-td2114537.html
>>> https://groups.google.com/forum/?fromgroups=#!topic/erlang-programming/4DBmCK4GAK8
>>> But my concern is slightly different. I have a separate
>>> sending/receiving process, P1, for a gen_tcp socket which receives messages
>>> it has to send, from process P2. There is no acking between the P1 and P2.
>>> Data is buffered at P2 and data acking is client driven, i.e that client
>>> says how much data it has received when it reconnects. Right now, P2 sends
>>> data to P1 as soon as it generates any data, and also adds it to its
>>> buffer, so that it can send it to the client if the socket gets closed
>>> before client receives it.
>>> The issue is, since the gen_tcp send call is blocking, and P2 might
>>> flood P1s mailbox at times, received messages(socket in active once mode)
>>> from the client are delayed quite a bit.
>>> What is the best way to handle this?
>>> Regards,
>>> Satyam Shekhar
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