Workaround for logger exception

[ghost]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	NA
Primary OS tested on	Ubuntu
Robotic platform tested on	Turtlebot 3 in Gazebo

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Description of contribution in a few bullet points

• This works around Exception being thrown: failed to initialize rcl node: Logger already initialized for node ros2/rcl#375. This was causing our system test to fail consistently. Our system test should pass again with this workaround.
• This replaces Disable unstable system test in Travis. #527 as a better alternative.
• The problem with this PR is that the use_sim_time parameter cannot be changed from the command line. Instead, if you want to use real time, you must manually change the nav2_params.yaml file. To fix this, we need to upgrade the ros2 launch tool, which is in the works.
• One last point. I did not apply the workaround to the map_server node. Due to fortunate circumstances, this node is not affected by the issue. By not applying the workaround, we are able leave the map file name as a parameter to the launch file.

[mkhansenbot]

Something seems strange that this passed even though it uses the nav2_system_tests/params/nav2_params.yaml file and you didn't update that file to set use_sim_time=True. Am I missing something? How is this passing?

[ghost]

It passes because the test_system_node.py code sets use_sim_time = true on nodes in all three namespaces. I believe that causes everything to switch to sim_time.

It is basically the same as what we were doing before we started setting use_sim_time in the launch file. We'd let everything come up, then set the parameter on one node, and all the nodes would see it and switch.

[mkhansenbot]

If that's the case, we can just remove the params file from the parameters list for those nodes that are only setting use_sim_time: amcl, navfn and simple_navigator and it should still pass

[ghost]

Looks like you are correct. I just pushed that change.

[mkhansenbot]

Looks good to me, thanks Carl!

[sloretz]

I think this line is the only one that matters for working around ros2/rcl#375. The change to how parameters are passed doesn't look to be necessary.

[sloretz]

Ah never mind, I didn't realize launch required node_name when using this form of paramters

`[ERROR] [launch.LaunchService]: Caught exception in launch (see debug for traceback): If a dictionary of parameters is specified, the node name must also be specified. See https://github.com/ros2/launch/issues/139

[mkhansenbot]

@orduno or @SteveMacenski - can either of you approve so we can merge this and get the Travis master branch build back to green?

[ghost]

Since #538 seems to be working, I'm closing this one.