add explanation for ROS_DISABLE_LOANED_MESSAGES.

[fujitatomoya]

document for ros2/rcl#949

Signed-off-by: Tomoya Fujita Tomoya.Fujita@sony.com

[fujitatomoya]

@wjwwood @clalancette requesting review.

[fujitatomoya]

@wjwwood @clalancette requesting review.

[clalancette]

I don't think that this information should be in this particular tutorial. This is the very first beginner tutorial, and we don't want to overload people with a bunch of advanced information about configuring their libraries.

I would suggest that this belongs either in one of the more advanced tutorials or in a How-To Guide.

[wjwwood]

I agree this seems like we're hijacking this beginner tutorial in order to turn it into a reference for all the environment variables that can be used to configure ros 2, when we should just have a reference page for that (not a tutorial).

Do we already have such a page?

[wjwwood]

I could see putting a new page in either "How-To-Guides", something like "how to disable loaned messages", or in "Concepts", something like "loaned messages" which describes generally what they are and as part of that how to use this environment variable to control them.

Or we could have a reference page with all the environment variables you could use with ros 2, where one of them is this env var, but I don't know where that would live.

@clalancette what do you think?

[fujitatomoya]

thanks for the comment. I understand this is not really tutorial... 😅

a new page in either "How-To-Guides", something like "how to disable loaned messages", or in "Concepts", something like "loaned messages" which describes generally what they are and as part of that how to use this environment variable to control them.

sounds good to me.

[clalancette]

I could see putting a new page in either "How-To-Guides", something like "how to disable loaned messages", or in "Concepts", something like "loaned messages" which describes generally what they are and as part of that how to use this environment variable to control them.

Yeah, that works for me too. I think it would be nice to have a page showing all of the possible environment variables that can be used with ROS 2, but I think that would be a long list, and is out-of-scope for this particular change.

[fujitatomoya]

@clalancette @wjwwood could you take a look again?

[fujitatomoya]

@wjwwood @clalancette

this is last one related to ROS_DISABLE_LOANED_MESSAGES, either of you can review?

[clalancette]

This looks good to me now, thanks.