Load model during runtime: how to run model plugins?

[osrf-migration]

Original report (archived issue) by Diego Ferigo (Bitbucket: dgferigo).

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The support of loading models during runtime was implemented months ago in PR143.

It doesn’t seem that the UserCommands system has the support to load a plugin if its element is included in the SDF file passed to the protobuf message. In fact, it seems being ignored. Is there any way to do it? In other words, is there any way to load a system defined in a plugin during runtime?

Btw: I know that there is Server::AddSystem, that it only requires the server not being in running state. Using this call, though, is not optimal because the system would be added in the world SDF context and it would require manually loading the plugin library. Even more relevant, it would be impossible to pass any configuration to the plugin like the one that could be passed with custom XML properties listed in the plugin SDF element.

[osrf-migration]

Original comment by Diego Ferigo (Bitbucket: dgferigo).

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• Edited issue description

[osrf-migration]

Original comment by Diego Ferigo (Bitbucket: dgferigo).

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I found that due to a problem in the SDF generation from C++ code, the plugin SDF element was not correctly inserted in the DOM of the object I was sending.

The responsible of processing the sdf::Model* object and creating its entities and components is SdfEntityCreator.hh, which has the support of loading model plugins. Therefore, this issue can be closed.

What’s still missing, instead, is the plugin unloading when the model is removed from the world. The object exposing the gazebo::System which loaded from the plugin is deleted only when the ignition::gazebo::Server is destroyed in the end of the simulation. It might create an effect similar to a memory leak if the process of adding and removing models is repeated hundreds of times. Instead, from what I know, entities should be cached.

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[osrf-migration]

Original comment by Louise Poubel (Bitbucket: chapulina, GitHub: chapulina).

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Diego Ferigo (dgferigo) , glad to hear you figured out how to load plugins at runtime.

What’s still missing, instead, is the plugin unloading when the model is removed from the world.

That's correct. I don't think there's an issue ticketed for this yet, and I didn't find a TODO in the code, but for sure the team has discussed this before. I just don't remember right now if we were missing some functionality in ign-plugin or if it's just a matter of implementing it in ign-gazebo.

[osrf-migration]

Original comment by Diego Ferigo (Bitbucket: dgferigo).

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@chapulina Thanks for the feedback. Right now the plugin unload during model removal is not a blocking feature for us, though on the long run it would be a nice addition.

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[osrf-migration]

Original comment by Diego Ferigo (Bitbucket: dgferigo).

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• changed state from "new" to "resolved"

Closing the issue since it has been solved