Make the start command print the endpoint on stdout

[tobim]

📔 Description

This is helpful for test scripts that pass in :0 to get a random free port allocated from the operating system.

📝 Checklist

• All user-facing changes have changelog entries.

[dominiklohmann]

This needs a changelog entry, and it also needs the start command documentation to be updated accordingly.

[mavam]

This feels like a not-so-nice hack. Let's try to find an alternative, or at least make it conditional on a given flag that we have to pass.

[tobim]

This feels like a not-so-nice hack. Let's try to find an alternative, or at least make it conditional on a given flag that we have to pass.

This allow us to write:

coproc nodefd {
  vast --verbosity=quiet -e :0 start
}
read -u "${nodefd[0]}" endpoint
# node is listening now
vast -e $endpoint status
...
vast -e $endpoint stop

To me this seems like very reasonable behavior and definitely not a hack. Note that reading from stderr instead is not that easy, because the buffer would eventually fill up and block the logging thread of the node in a write operation.

[mavam]

I understand where you are coming from, but I disagree that this warrants unconditional printing to stdout. Does anything speak against introducing an option that triggers this behavior, e.g., --print-bound-port? It's not a common case but as big consequences for launch tools that process stdout.

Also, how does your patch interact with log level "quiet"?

[dominiklohmann]

This feels like a not-so-nice hack. Let's try to find an alternative, or at least make it conditional on a given flag that we have to pass.

To me, this feels like the proper way to solve this problem. It's the natural way to solve it for improved scriptability.

However, I also agree that this should be behind a flag, e.g., vast.start.show-port, and that flag should default to false.

Also, how does your patch interact with log level "quiet"?

It shouldn't have anything to do with log levels, this is printing to stdout so it can be processed by the caller. It necessarily has to be on a separate channels from regular log output.

[mavam]

Looks good, just a few word smithing tweaks.