ros2 topic {bw|delay|hz} don't support --no-daemon

[scpeters]

Feature request

Feature description

Support for the --no-daemon command-line argument was added to several of the ros2 topic verbs in #514, but it is not yet provided for the bw, delay or hz commands. It's also not available for pub, but I'm not sure if that matters.

Implementation considerations

[fujitatomoya]

I think that question is we need to NodeStrategy for these command options.

not yet provided for the bw, delay or hz commands. It's also not available for pub

I believe that all these sub-commands are used when we already know the topic is available via ros2 topic list or find, and then those sub-commands actually need to connect to the endpoint (not discovery configuration or graph). so i do not really think of the use case even for these...

any thoughts?

[scpeters]

ok, please close this issue if it is not valid. I don't really understand how the tools work on the inside; I just noticed an asymmetry in the CLI flags for some of the verbs and thought they could be made more consistent

[fujitatomoya]

@scpeters thanks for sharing your thoughts. i will close this for now, but there would be other opinion, and feel free to reopen!

[clalancette]

Yeah, it turns out that we basically use the daemon for caching discovery information, so that commands like ros2 topic list return all of the topics in the system. In the case of commands where we don't need everything in the system, we don't use the daemon, and in that case we also don't need the --no-daemon command-line argument. I believe that applies to all of bw, delay, and hz; they will all wait around for a particular topic, and hence don't need to use the daemon at all.

All of that is to say that I don't think we need to do anything here. But thanks for bringing it up.