Re: [opendds-main] Problem with QoS Policies

[Alex D. <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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