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InsertModelSDF potential race condition

asked 2014-12-16 00:47:23 -0500

mkoval gravatar image

I am trying to programmatically add objects to an environment with InsertModelSDF. There seems to be a race condition that causes this to sporadically fail if InsertModelSDF is called too quickly after init_world. This test script reliably fails on the first iteration and, additionally, sometimes fails on the second iteration of the loop:

Additionally, I noticed a few other quirks that are potentially relevant:

  1. GetModel only returns the new model after runWorld has run for at least one timestep.
  2. There is no reliable way of telling if InsertModelSDF failed.

Am I doing something wrong in my test script (e.g. neglecting acquire a lock)? Also, is there any way to force this data to refresh without running a simulation timestep?

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In your test script you don't declare `model_path`. Can you fix it?

NickDP gravatar imageNickDP ( 2014-12-16 15:31:33 -0500 )edit

I accidentally removed that line when cleaning up the code. It's fixed now (same URL).

mkoval gravatar imagemkoval ( 2014-12-17 01:26:51 -0500 )edit

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answered 2014-12-16 14:05:57 -0500

NickDP gravatar image

Regarding your additional questions, my question and nkoenig's answer here is relevant.

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This is likely the source of the issue. However, I am not sure why. I am manually triggering simulation timesteps with the gazebo::runWorld function. Shouldn't this force processing of the queue?

mkoval gravatar imagemkoval ( 2014-12-16 14:54:59 -0500 )edit

answered 2014-12-17 10:31:59 -0500

nkoenig gravatar image

This happens because we don't process messages every iteration of simulation. Our strategy is to let messages that don't need immediate processing to linger a bit. The effect is a small delay in things like inserting new models, with more time given to the physics engine.

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Thanks! What is the recommended way of waiting for the model to be inserted? @NickDP's post uses a spinlock to wait until GetModelCount() increases. I am attempting to use Gazebo programmatically (in-process), so it is undesirable to trigger several physics updates every time I add a model. Ideally, I'd like to run the message processing manually (without also triggering a simulation step).

mkoval gravatar imagemkoval ( 2014-12-17 11:07:37 -0500 )edit

You should be able to listen to the ~/model/info topic. Or you can connect to the addEntity event.

nkoenig gravatar imagenkoenig ( 2014-12-17 11:14:04 -0500 )edit

Thanks. The `AddEntry` event looks like what I want. Is there any way to process the message queue without also triggering a simulation step?

mkoval gravatar imagemkoval ( 2014-12-17 11:35:33 -0500 )edit
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Asked: 2014-12-16 00:47:23 -0500

Seen: 386 times

Last updated: Dec 17 '14