Re: [opendds-main] Problem with QoS Policies

[Massimo P. <mas...@gm...>]

Just loop calling take_next_sample until you get a no_data_available result.
Otherwise you should use the data reader take operation passing a sequence
of SampleInfo and the appropriate view status.

Massimo

2014-11-27 15:57 GMT+01:00 Alex Douckas <ale...@gm...>:

> Hello again,
>
> I forgot to mention that the Publisher application has a WaitSet and
> does not start transmission until a Subscriber is present, so a) is
> not the case.
>
> For b) , I think it's not the case either, since the default values of
> durability_service max_samples and max_instances are LENGTH_UNLIMITED.
>
> As far as c) is concerned,  what is the correct loop condition to read
> the data samples that are queued in the data reader cache ?
>
> Kind Regards,
> Alex
>
> On Thu, Nov 27, 2014 at 4:20 PM, Massimo Pichini
> <mas...@gm...> wrote:
> > Hi there,
> >
> > I see a some potentials causes of your problem:
> >
> > a) DataWriter start publication before the association with the
> DataReader
> > is setup. In this case all samples published before the association is
> > established are lost, unless you enable support for late subscribers in
> the
> > data writer setting the Durability QOS to at least
> > TRANSIENT_LOCAL_DURABILITY;
> > b) the Durability Service QoS max_xxx enforce a lower level of max
> > samples/instances that can be kept in the data writer cache
> > c) the on_data_available callback should invoke the take_next_sample in a
> > loop otherwise samples queued in the data reader cache can remain
> > unprocessed
> >
> > best regards
> > Massimo
> >
> >
> >
> > 2014-11-27 10:02 GMT+01:00 Alex Douckas <ale...@gm...>:
> >>
> >> Hello,
> >>
> >> I have created a publisher application and a subscriber one ( both in
> >> C++ ) with the following QoS policies on both Topic and DataWriter (
> >> and DataReader respectively ) :
> >>
> >> DDS::TopicQos default_topic_qos;
> >> participant->get_default_topic_qos(default_topic_qos);
> >> default_topic_qos.history.kind = DDS::KEEP_LAST_HISTORY_QOS;
> >> default_topic_qos.history.depth = 140000;
> >> default_topic_qos.reliability.kind = DDS::RELIABLE_RELIABILITY_QOS;
> >>
> >> DDS::DataWriterQos dw_default_qos;
> >> pub->get_default_datawriter_qos (dw_default_qos);
> >> dw_default_qos.history.kind = DDS::KEEP_LAST_HISTORY_QOS;
> >> dw_default_qos.history.depth = 140000;
> >> dw_default_qos.reliability.kind = DDS::RELIABLE_RELIABILITY_QOS;
> >>
> >> Now, the publisher is sending about 3000 data samples, each one every
> >> 100 miliseconds. So to test the history and reliability policies, I
> >> set a delay on the subscriber ( with usleep) of 500 miliseconds on the
> >> "on_data_available" class like this :
> >>
> >>       DDS::SampleInfo si ;
> >>       DDS::ReturnCode_t status = measurement_dr->take_next_sample(data,
> >> si) ;
> >>
> >>       if (status == DDS::RETCODE_OK) {
> >>          //omitted Code that manipulates the data sample
> >>
> >>              usleep (500000);
> >>
> >>        } else if (status == DDS::RETCODE_NO_DATA) {
> >>         cerr << "INFO: reading complete after " << count << " samples."
> <<
> >> endl;
> >>         break;
> >>       }
> >>
> >> The problem is that after about 1000 received samples, the subscriber
> >> somehow stops receiving the rest samples. Since the depth of History
> >> is bigger than the samples, the subscriber should receive everything.
> >> The same thing happens even if I use KEEP_ALL_HISTORY instead of
> >> KEEP_LAST. Do you have any idea about this issue ?  Am I using the
> >> policies wrong ?
> >>
> >> Thanks,
> >> Alex
> >>
> >>
> >>
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> >
> >
> >
> > --
> > Massimo
> >
> >
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-- 
Massimo