[zeromq-dev] Question about the PUBSUB design pattern when server restarts.

[Chuck Remes]

On Nov 15, 2010, at 2:11 AM, Pieter Hintjens wrote:

> Hi Janak,
> 
>>   Do I have to call connect from client side after every s_recv call ?
> 
> No, you call once and 0MQ will reconnect to the publisher
> automatically.  You can try this with the wu example.
> 
>>   Currently, I see that if I dont call connect on SUB and PUB stops and 2
>> minutes later starts again, memory usage on pub keeps on increasing ? May
>> be, its because it might be keeping it in queue for the sub to get the data.
> 
> I'm not sure about your description here.  If pub stops, how can its
> memory usage keep on increasing?
> 
> If pub stops, sub will finish processing whatever data was in-flight,
> and then stop.  When pub starts again, it will send to all subs that
> (re-)connect to it.  They'll reconnect automatically as soon as they
> find the pub socket is available again.

I discussed this issue with Janak on IRC. When he says that the publisher "stops" he means that the process goes down. Two minutes later he restarts it but the subscribers do not see any further messages.

In this case the publisher is BINDing to the endpoint while the subscribers are all CONNECTing. I suggested putting a FORWARDER device in between so that publishers and subscribers could come and go without destroying the endpoints which is what was happening in his original scenario.

cr