[zeromq-dev] Publishers stops sending data after sometime. Subscriber is required to fix publisher

Tobias Elbert tobias_elbert at hotmail.com
Sat Jan 27 14:05:20 CET 2018


Hi Ravi,


I recall having had this problem a while ago, too, in another project. I was using C# clrzmq3 bindings on either side. I never solved it directly but from memory I recall sending down heartbeats and once a subscriber hadn't received a heartbeat message for X seconds, I restarted it.

Cheers
Tobias

________________________________
From: zeromq-dev <zeromq-dev-bounces at lists.zeromq.org> on behalf of Ravi Joshi via zeromq-dev <zeromq-dev at lists.zeromq.org>
Sent: Saturday, January 27, 2018 11:27 AM
To: ZeroMQ development list
Cc: Ravi Joshi
Subject: Re: [zeromq-dev] Publishers stops sending data after sometime. Subscriber is required to fix publisher

Hi Justin,

I will check it using netstat.

Meanwhile, ZMQ_TCP_KEEPALIVE seems not working. I still see that after some time, Windows OS, where publishers are running, is showing 0 MBPS transmission rate. After I restart subscribers in ROS on Ubuntu, publishers start working. Please note that during this process I am not restarting publishers at all.

Below is the code snippet added to all subscribers-

int tcp_keepalive = 1;
zmq_socket.setsockopt(ZMQ_TCP_KEEPALIVE, &tcp_keepalive, sizeof(tcp_keepalive));

 -
Thanks
Ravi



On Saturday, 27 January 2018 5:36 PM, Justin Karneges <justin at karneges.com> wrote:


One thing you might do is run netstat on both sides to see if the connections are still listed. In a dead connection scenario, netstat should no longer list the connection on the PUB side, but should remain listing it on the SUB side.

Note that it can take time for the PUB connection to give up. On Linux, the default is something like 20 minutes after it dies, so give the PUB side some extra time after messages stop transmitting. If transmission hasn't worked for over 20 minutes and netstat is still showing the connection on the PUB side, then the problem may be something else.

On Sat, Jan 27, 2018, at 12:13 AM, Ravi Joshi via zeromq-dev wrote:
Hi Justin,

Thank you very much. How do I make sure that I am getting dead connections?

For time being, I am enabling ZMQ_TCP_KEEPALIVE on all 3 SUB sockets.

I will tell you the status of it after sometime.

Thanks
-
Ravi
Sent from Yahoo Mail for iPhone<https://overview.mail.yahoo.com/?.src=iOS>

On Saturday, January 27, 2018, 3:27 PM, Justin Karneges <justin at karneges.com> wrote:
Hi,

One issue with socket types that don't usually write data (such as SUB) is that a dead connection might go unnoticed forever. You can work around this by enabling TCP keep alives on the SUB socket. I don't know if you're getting dead connections here but just thought I'd mention it.

Justin

On Fri, Jan 26, 2018, at 9:33 PM, Ravi Joshi via zeromq-dev wrote:
> Hi,
>
> I am using Publisher-Subscriber pattern consisting of 3 publishers to
> publish 3 different types of data. All 3 publishers are written in a
> single C# file. However, each subscriber is written in a separate C++
> file inside ROS. From the point of ZeroMQ, there is no difference in
> each subscriber, since context, socket initialization and receiving
> message is done in the same way for all subscriber. Hence, in order to
> make the mail shorter, I am just posting code snippet of 1
> subscriber below.
>
> The publisher code in C# snippet is available in Pastebin
> (https://pastebin.com/S65LmwuV).
> The subscriber code in C++ snippet is available in Pastebin
> (https://pastebin.com/xb3V0n0u).
>
> The publisher works well initially for some time and successfully
> transmits data at 700MBPS rate but stops transmitting any data after 5-6
> hours.
>
> In order to make publisher working again, I need to restart the
> subscribers. This is strange to me since it is unexpected behavior as
> per the Publisher-Subscriber pattern is concerned.
>
> Why such weird behavior? Any workaround, please.
>
> -
> Thanks
> Ravi
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