[RoboMaker] Where to get ROBOMAKER_ROBOT_APP_IP and ROBOMAKER_SIM_APP_IP when running a simulation job with images

Question

I'm following the tutorial in https://docs.aws.amazon.com/robomaker/latest/dg/run-hello-world-ros.html and have successfully build the images, pushed to ECR and created simulation job with them.

However when running the simulation job, both instances needs to be told where their respective IP are beforehand, which it's usually available after the simulation job is running.

So is it possible to know which IP the instances is getting assigned before the instances are up and running?

Answer

Hello @AWS-User-0325661

We recently published a new [blog article](https://aws.amazon.com/blogs/robotics/preparing-ros-application-and-simulation-containers-for-aws-robomaker/) that describes in depth the process to create and run ROS docker containers in AWS RoboMaker. Hopefully this can be a helpful resource!

Once a [VPC is configured](https://docs.aws.amazon.com/robomaker/latest/dg/vpc.html), the IP of the underlying simulation job should be available when using **Type: General** (your container image) via the environment variables `ROBOMAKER_SIM_APP_IP` and `ROBOMAKER_ROBOT_APP_IP`.

In the blog, we include a sample **JSON** file with parameters for `create-simulation-job`. Here, we set the following environment variables.

```
"ROS_IP": "ROBOMAKER_SIM_APP_IP",
"ROS_MASTER_URI": "http://ROBOMAKER_ROBOT_APP_IP:11311",
"GAZEBO_MASTER_URI": "http://ROBOMAKER_SIM_APP_IP:11345"
```

In ROS1, this will enable you to connect the Robot and Simulation Application containers together, on a shared ROS core.

If it is an external process requiring the IP address, you could use AWS Step Functions to launch the simulation jobs (either individually, or in a batch) - then run [DescribeSimulationJob](https://docs.aws.amazon.com/robomaker/latest/dg/API_DescribeSimulationJob.html) API call (through a Lambda function using boto3 as an example) to get the list of IPs for a given job in the `networkInterface` attribute.

[RoboMaker] Where to get ROBOMAKER_ROBOT_APP_IP and ROBOMAKER_SIM_APP_IP when running a simulation job with images

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