Re: [Discuss-gnuradio] Debugging ControlPort/Thrift problem (Re: costas ambiguity and correlate-and-sync block in qpsk)

[Tom Rondeau]

On Sun, Apr 3, 2016 at 8:49 AM, Andy Walls <address@hidden> wrote:

> Otherwise, you didn't drop a control port related block on the
> flowgraph did you?


Here is some good info on how GRNURadio's control port works at a high
level:
https://gnuradio.org/redmine/projects/gnuradio/wiki/ControlPort
https://gnuradio.org/doc/doxygen/page_ctrlport.html

>From that second page, it appears that running two flowgraphs on the
same machine has a problem caused by Apache Thrift and GNURadio's
configuration of the Control Port network port (default of 9090).
https://gnuradio.org/doc/doxygen/page_ctrlport.html#ctrlport_thrift_issues

So please only run on flowgraph at a time, at first, to troubleshoot
this issue.

Second, you may want to try setting the GR_CONF_THRIFT_PORT environment
variable to something other than 9090, a port that you know is open on
your machine, for each separate flowgraph that you run.

FYI, the modulate_vector block runs a "mini"-flowgraph, before the main
flowgraph actually runs:

https://github.com/gnuradio/gnuradio/blob/master/gr-digital/lib/modulate_vector.cc#L59

Hopefully, there isn't some sort of weird race condition with the Thrift
port being open for the modulate_vector block's mini-flowgraph and the
main flowgraph.


Hi Tom,

Do you have any comments or insights on Arik's Thrift error message
and/or the possibility of modulate_vector's mini-flowgraph causing
problems with Thrift's network port and the main flowgraph?

Regards,
Andy

Andy,

I think you've got it on the Thrift issue. However, running the modulate vector mini flowgraph first should kill itself immediately and free up the port, so I don't think that's the problem. On the other hand, I've been seeing issues recently where every time I launch GRC, it seems to cause a conflict with whatever port I'm setting. Almost as though GRC is launching something and holding on to the port specified in the thrift.conf file. I thought this could just be a problem on my laptop (I've been traveling a lot -- more than usual even -- and developing on my laptop can lead to me doing a lot of crazy things), but I think I've since seen it on my office workstation as well. That could be a problem here, too. We'll have to track that down.

Using the GR_CONF_THRIFT_PORT variable is a good idea to set the port per flowgraph you're running. Another option is to set the port to 0 in thrift.conf, which will cause Thrift to open an ephemeral port for each server is creates. You'll just have to pay attention to the message output that announces the ControlPort endpoint to find out what port it's running on.

Tom