ROS2, docker and IPC

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Hello!

I'm using docker-compose to run multiple ROS2 nodes (Foxy, FastDDS, cpp) in different services. The services use the following settings in the docker-compose file:

• network_mode: "host"
• ipc: host
• pid: host

Nodes are created using the 'use_intra_process_comms(true)' option.

1) My understanding is that these settings (above) shall suffice to enable the nodes to use IPC when communicating between containers?

What happens to the IPC if:

2) A node on the host machine subscribes to a topic published by a container node? Is IPC still used?

3) A node on a remote host on the network subscribes to a topic published by a container node? Will the topic move over to multicast?

Bonus question:

4) Assuming rosbag2 runs in a container, will it be able to benefit from IPC?

Many thanks!