[rabbitmq-discuss] Java client: closed connection doesn't raise exception immediately

[carlhoerberg]

Ok, yes, suspected it had with to do with the underlaying TCP stack, thank you for the detailed explanation! 



On Tuesday 7 May 2013 at 14:58, Tim Watson-6 [via RabbitMQ] wrote:

> Hi, 
> 
> On 7 May 2013, at 04:32, carlhoerberg wrote: 
> 
> > It looks like the rabbitmq java client doesn't raise an exception as soon as 
> > a connection fails, eg. due to network cable disconnection. 
> > 
> > The following code will continue to run for 2 minutes after the 
> > disconnection, and first then raise an exception. 
> 
> 
> That's perfectly normal, for a network driven application. It is not RabbitMQ's client library that wait's to throw an exception, but rather it is the operating system's network stack that takes time to determine that a peer socket is no longer available. This can take many minutes, even when you're connecting via the loopback interface (i.e., localhost) for testing. 
> 
> On most unices, the relevant bits of `man tcp` are: 
> 
> "When a network error occurs, TCP tries to resend the packet. If it 
> doesn't succeed after some time, either ETIMEDOUT or the last received 
> error on this connection is reported." 
> 
> In that second sentence, "after some time" is determined by the OS kernel configured limits, viz tcp_retries1 (defaults to 3 on linux) and tcp_retries2, and the configured retransmission timeout. Of course there are doubtless other parameters that interact with this behaviour. So you're quite lucky because it's a producer application that's trying to send - those time out much faster. For network consumer applications, this problem is quite a tricky on because the default settings on linux for example, mean delays of between 10 and 30 minutes before the OS networking layer "notices" the connection has timed out. 
> 
> This problem is, of course, not specific to RabbitMQ. 
> 
> Cheers, 
> Tim 
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