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Questions tagged [queue]

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remove old messages from topic

Hi all, I am using ROS kinetic on Ubuntu 16.04. I have a topic that I publish movement instructions to. At some point in my code I want to make a long rospy.sleep but sometimes I will publish to the ...
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RS232 Queue System in ROS

Using ROS Kinetic and primarily python. I have a driver that subscribes to several topics including /cmd_vel and a bunch of other commands which interact with a control board via RS232. One problem I ...
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1 answer
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How to pull a message from queue with time interval?

When I subscribe my node, I set messages queue size and callback function: ...
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3 answers
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How to Detect Subscriber Drops a Message

I made a subscriber which reads LIDAR data from rosbag-play. I use C++(roscpp). But when I do rosbag-play with normal speed, subscriber's callback function cannot catch up with LIDAR stream speed, ...
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Which data is thrown away in queue if publish and spinonce rate is different?

I read that SpinOnce does not only make callback, but it will also clean the queue if possible. is that right? Let's say publisher publish alphabets (a,b,c,...) at 9hz, and subscriber call Spinonce at ...
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1 answer
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Multiple subscriber queue allocation using the same callback

I am creating multiple subscribers using the same callback function as in this post, the code is here. Basically is this: ...
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1 answer
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When to use publisher queue size vs. subscriber queue size

Although most tutorials only discuss the publisher queue size, a subscriber has such a parameter as well. So I'm wondering: When to use which queue size? Actually the subscriber seems to be the ...
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1 answer
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Queueing positions for the robot to move to

Hi, I would like to have the robot move to point a->b->c in order and am not sure how to do this using a simple action client. I'm using movebase for this. When I add a second position for the ...
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1 answer
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roscpp: requesting current queue state of subscriber

I have a node, where I would like a subscriber to have a high queue size during initialization of some internal processors (during which my node intentionally lacks calling into ros spinner) to avoid ...
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1 answer
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simple FIFO stack (queue) for MoveIt in ROS

Hi, I want to use a simple queue (FIFO stack) to give a list of waypoints to MoveIt. I looked at the tutorial : Callbacks_and_Spinning and the class CallbackQueue but it looks like we can use it only ...
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1 answer
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Current pub/sub queue length

Dear all, what if I would like to know how many objects are currently in the publisher's queue or in one of the subscribers' queue? I would like to monitor if they gets too long (and, e.g., some ...
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1 answer
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Subscriber data not up to date

I have written a subscriber to one of the image topics and I have set my buffer to 1 using: subscriber =rospy.Subscriber("/camera/rgb/image_mono/compressed",CompressedImage, callback, ...
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1 answer
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how are threads used to service callbacks in nodelets?

I have several nodelets, each subscribes to different messages (using the single threaded node handle). However, I realized one of my nodes, which subscribes to images and to odometry messages, and ...
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1 answer
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Can you check how many messages are in a subscriber's Queue?

For testing purposes, I want to plot the number of messages waiting in a subscriber's topic Queue over time. Having too many old messages is undesirable since up to date information is critical. ...
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1 answer
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Queued messages do not get sent when shutting down a publisher

I noticed that when calling publisher.shutdown(), the messages that are queued for publishing simply get destroyed with the publisher. I could not find any ...
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1 answer
3 views

subscriber queue length

I understand that ROS queues all incoming messages until nodes are able to service those callbacks and that this queue length is specified in the constructor of a subscriber. But what I would like to ...
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1 answer
38 views

RVIZ Message Filter Queue Size

I have a setup where my pose information is greatly delayed ~0.5s from my PointCloud data. Because of this, my TF timestamps lag behind by about the same 0.5s. When I attempt to visualize this in ...
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1 answer
20 views

Know if you are dropping messages from a subscriber queue?

Is there a way to know when or how many messages are being dropped from a subscriber queue? I'm mostly interested in occasionally reporting that node foo has dropped N packets since execution began. ...
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2 answers
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What happens is a node receives a message while it's in the middle of a callback?

I'm thinking of having a node send a message to another node as part of a callback function. It should receive a message from another node at about this time as well, before it finishes the callback ...
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1 answer
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Do subscribers work on a FIFO queue?

Do the queues used in ros::Subscriber behave like FIFO queues? In particular, if I use a message_filters::Synchronizer that, in approximately equal time increments, invokes a callback function for a ...
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1 answer
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how does second term of advertise

Hello. I'm writing a program that reads data from a laser. This information is published by stage or a bag file. I know that the second parameter of the function advertise() or subscribe() is the size ...
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