[zeromq-dev] does 0mq keep-alive for connections?

[Attila-Mihaly Balazs]

This sounds like this problem: 
http://www.evanjones.ca/tcp-stuck-connection-mystery.html (tl;dr 
version: the final ack packet gets lost when establishing the connection 
but the loss doesn't get detected until actual data is sent).

AFAIK 0mq doesn't do heartbeating on its own, so it can't detect this 
situation without extra user code.

Regards,
Attila Balazs
> sem33 at yandex-team.ru said:
>> 21.01.2012 01:56, Sergey Matveychuk wrote:
>>> clients. netstat -a on server shows no connection with a client, but on
>>> the client netstat -a shows an established connection:
>>>
>> I think the patch will resolve my problem.
> As Martin Sustrik says, SO_KEEPALIVE is probably not what you want. You can
> do heartbeating/keep-alive at the application level instead.
>
>> --- src/ip.cpp.orig	2012-01-22 15:17:01.000000000 +0400
>> +++ src/ip.cpp	2012-01-22 15:21:21.000000000 +0400
>> @@ -49,6 +49,13 @@
>>       if (s == retired_fd)
>>           return retired_fd;
>>
>> +    // Turn keep-alive on for TCP
>> +    if (protocol_ == IPPROTO_TCP) {
>> +	int optval = 1, optlen = sizeof(int);
>> +	int rc = setsockopt (s, SOL_SOCKET, SO_KEEPALIVE,&optval, optlen);
>> +	errno_assert (rc != -1);
>> +    }
>> +
>>       //  If there's no SOCK_CLOEXEC, let's try the second best option. Note that
>>       //  race condition can cause socket not to be closed (if fork happens
>>       //  between socket creation and this point).
> open_socket() is not the right place to put this. I'd probably add a
> keepalive_socket() and call that in the same places from where
> stream_engine_t calls unblock_socket().
>
> -mato
>
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