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topic_tools: throttling when rostime jump backward #1397

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merged 1 commit into from
May 18, 2018

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furushchev
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Closes #1396

  • Reset internal variable on rostime moving backward
  • Added test code for the situation

@mikepurvis
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Should there be some kind of threshold for the jump, or at least a flag to disable this behaviour? I'm thinking a default that the jump-back-in-time logic is only triggered for a delta > 1s or something.

Admittedly, I may be grasping at straws here, but I'm imagining a scenario where two separate machines are publishing the same topic with slightly offset clocks, or even with the same clock but network lag which causes the messages to interleave.

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@tfoote tfoote left a comment

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If time moves backwards it's definitely an event. Realistically you should never have two clocks publishing, that's basically guarenteed to cause bad behavior due to interleaving. And non-monotonic clocks will wreak havoc hear and elsewhere.

This is the same logic that tf users to clear the buffer: https://github.com/ros/geometry2/blob/melodic-devel/tf2_ros/src/transform_listener.cpp#L105

@@ -126,6 +126,11 @@ void in_cb(const ros::MessageEvent<ShapeShifter>& msg_event)
now.fromSec(ros::WallTime::now().toSec());
else
now = ros::Time::now();
if (g_last_time > now)
{
ROS_WARN("Detected jump back in time.");
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This should state what it's doing, not just that it detected. Something like "Detected jump back in time, resetting throttle period to now for ***."

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@mikepurvis @tfoote Thank you very much for your review!

@tfoote I updated the message. Please check. 👍

@furushchev furushchev force-pushed the throttle_backward branch from e5131d1 to 0bbc1fe Compare May 15, 2018 02:06
@tfoote
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tfoote commented May 15, 2018

lgtm, we don't really have a way to address the throttle instance so at least it's know that some throttle will be updated.

@dirk-thomas
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Thank you for the patch.

@dirk-thomas dirk-thomas merged commit 231f3e4 into ros:melodic-devel May 18, 2018
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4 participants