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Wait For the API calls in a world plugin

asked 2018-06-18 09:37:38 -0600

TTDM gravatar image


It's pretty clear that the API calls are asynchronous when called inside the worldUpdate function.

I was wondering if there a exist a function that can be used to wait for the end of the calls ?

The idee behind it would be to pause the simulation, call a few function from the API, advance from one step while knowing that the previous calls have been executed, then call new API functions, etc.

Thanks a lot for anyone that can help, TTDM

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What API calls are you referring to? Usually things which don't use transport shouldn't be asynchronous.

chapulina gravatar imagechapulina ( 2018-06-18 12:42:17 -0600 )edit

For exemple a spawn model. If I do the 2 following step: - "spawn a heigthmap using insertModelSdf (or string)" - "get the height of the heigthmap", this function crash because the heightmap does not exit. What i do at the moment is if start it right after OR on the next "au update" callback. What I currently do is to wait for 500 iterations before using the heigthmap.

TTDM gravatar imageTTDM ( 2018-06-19 03:00:55 -0600 )edit

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answered 2018-06-19 12:23:17 -0600

So what's happening is that Gazebo is putting your insert instructions in a queue this->dataPtr->factoryMsgs which gets processed in a future iteration, based on this->dataPtr->processMsgsPeriod.

It looks like you'll need to step a few iterations while checking that the model has been inserted, you could check World::Models() to see if the model has been inserted.

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Sorry for the delay of my answer. I wonder if there are not multiple queue such as this one which could create a behavior that appears asynchronous. At some point, I insert a model which contains a sensor (camera). When I destroy them, I start by calling SensorManager::RemoveSensors() then I call World::ClearModels(). I sometimes ( not systematic behavior ) get an error which basically says that the sensor cannot be remove because it does not exists. I guess it has been destroyed with the model

TTDM gravatar imageTTDM ( 2018-06-22 08:17:18 -0600 )edit

My main issue is that I repeat this Model+Sensor creation + destruction process and that sometimes, still not systematic, when I try to create the pair Model+Sensor, I have a core dump. It might not be clear without the code. If that's the case I will update my question in a few month when I will release the code as a part of an open source ros package. Anyway, thanks for the first answer !

TTDM gravatar imageTTDM ( 2018-06-22 08:24:06 -0600 )edit
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Asked: 2018-06-18 09:37:38 -0600

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Last updated: Jun 19 '18