Using Realtime Publisher in a for-loop
Hi everyone,
I don't have much experience with Realtime Publishers yet. So I can't understand the following behaviour:
I have a map of messages and want to publish each of them in a for-loop. For some reason, the following works as supposed:
for (auto& msg : map)
{
ROS_INFO("hello");
msg.second.header.stamp = ros::Time::now();
if (rt_publisher_->trylock())
{
rt_publisher_->msg_ = msg.second;
rt_publisher_->unlockAndPublish();
}
}
The map contains about seven elements and the loop is called at 100 Hz.
If I comment out the ROS_INFO it won't work. That is, there's no error, the messages just aren't being published. This does not depend on the publisher's queue size.
So my guess is that the publisher needs some time between to runs? What would be the best way to implement this?
Please explain why you chose a Realtime Publisher. How many messages per second are you trying to publish?
I've only seen this behaviour (ie: lost messages) with publishers (real-time or not) if the queue size is too small.
The fact adding a
ROS_INFO(..)changes the behaviour you observe does seem to point in the direction of subscribers taking longer than you give them to receive the messages.How many elements are in
mapon average? And what's the size of the queue?The loop is called 100 times per second, iterating over ~7 elements in the map. I tested it with queue sizes ranging from 1 to 1000, all with the same result.
I have to use the realtime publisher because the code shown is part of a ros controller requiring real time. To verify that the problem is due to the rt publisher I replaced it with the 'normal' publisher and everything worked well.