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fkie / multimaster_fkie

ROS stack with FKIE packages for multi-robot (discovering, synchronizing and management GUI)
BSD 3-Clause "New" or "Revised" License
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Help: sync /tf topic to another machine cause BufferCore::getLatestCommonTime get wrong time? #80

Closed zhouchengming1 closed 6 years ago

zhouchengming1 commented 6 years ago

Hello, all:

I use multimaster to sync some topics and nodes for two machines, but I found if I sync /tf topic from A to B machine , then the program on A will get wrong time from BufferCore::getLatestCommonTime. I don't know how it happens, anyone have idea? Thanks.

atiderko commented 6 years ago

Hi,

did you synchronize time between machines A and B? http://wiki.ros.org/ROS/NetworkSetup#Timing_issues.2C_TF_complaining_about_extrapolation_into_the_future.3F

zhouchengming1 commented 6 years ago

@atiderko No, I will try this. But I don't know why /tf topic synced to B machine could cause a problem like this? Does it get some time information from B when register?

zhouchengming1 commented 6 years ago

Does the multimaster sync node will modify the timestamp of local ros master ?

atiderko commented 6 years ago

master_sync does not modify any timestamps or other data or behaviour of ROS communication. If you synchronize /tf (and also other topics) the sender stay the same and publish tf messages from different hosts. The receiver of /tf get messages with different timestamps. I do not know if it will cause the BufferCore :: getLatestCommonTime error. It is just a guess!

If you use node_manager you can temporary synchronize the time and check if the error occurs with synchronized time.

zhouchengming1 commented 6 years ago

It seems that two rosnodes A and B are synced to another machine, A publish to /tf topic and B subscribe to /tf topic , so another data connection created on the remote machine? When I sync only needed topics, instead of the whole nodes, the problem is gone.