broken pub/sub connection by dynamic recreation of a publisher or subscriber

[rex-schilasky]

Problem Description

After introduction of the new fast unregistration mode (#1086) shm synchronization events between datawriter (sending process) and memfile observer (receiving process) are destroyed (shm_unlink) either by a stopped publisher or subscriber even the event is still used by "the other side" (either the shm data writer or the memfile observer).

This leads to a broken connection if a new publisher/subscriber is created dynamically using the same topic name again.

How to reproduce

1. Start ecal_sample_person_snd
2. Start this adapted ecal_sampl_person_rec variant

int main(int argc, char **argv)
{
  // initialize eCAL API
  eCAL::Initialize(argc, argv, "person subscriber");

  std::cout << std::endl << "FIRST RUN" << std::endl << std::endl; eCAL::Process::SleepMS(1000);
  {
    eCAL::protobuf::CSubscriber<pb::People::Person> sub("person");
    sub.AddReceiveCallback([](const char* /*topic_*/, const pb::People::Person& person_, long long /*time_*/, long long /*clock_*/, long long /*id_*/){std::cout << "person id : " << person_.id() << std::endl;});
    eCAL::Process::SleepMS(3000);
  }

  std::cout << std::endl << "SECOND RUN" << std::endl << std::endl; eCAL::Process::SleepMS(1000);
  {
    eCAL::protobuf::CSubscriber<pb::People::Person> sub("person");
    sub.AddReceiveCallback([](const char* /*topic_*/, const pb::People::Person& person_, long long /*time_*/, long long /*clock_*/, long long /*id_*/){std::cout << "person id : " << person_.id() << std::endl;});
    eCAL::Process::SleepMS(3000);
  }

  // finalize eCAL API
  eCAL::Finalize();

  return(0);
}

3. In the ´SECOND RUN´ the subscriber will not receive any data.

How did you get eCAL?

I don't know

Environment

• eCAL: 5.12
• OS: Ubuntu 20.04

eCAL System Information

No response