Ensure pipes loaded before serving

[robertgates55]

Currently, if I use the yaml upstream, and provide a config, it can take up to 90s for the pipes to 'load'. I'd like to find a safe way to ensure that it's 'ready' before it begins listening, to avoid failed username mappings.

Is it possible to enforce that the upstreams must be fully loaded prior to opening the listener?

Where should I be looking to put that change?

(Again - I'll likely be raising as a PR - just not sure where to look/put the necessary)