Support ddev list -j --continuous

[rfay]

What happened (or feature request):

The --continuous flag was added to ddev list to make it simpler (and lighter-weight) for ddev-ui to check the status of projects. Please change the main loop to support it.

What you expected to happen:

How to reproduce this:

Version: Please include the output of ddev version, docker version and the project's .ddev/config.yaml.

Anything else do we need to know:

Related source links or issues:

Please use a complexity rating of 1-5 (5 is high) for a feature request. (High complexity implies more PR planning)

[dclear]

Needs testing for performance: continuous v. noncontinuous.

[alkymst]

So if we scale the app back to check once every 2.5 seconds we seem to hit a sweet spot. I'll be pushing an update that rolls implements this for the time being as it's ahuge savings in perfomance until we can fine tune the ddev list -j --continuous itself.

I have been playing around with this and we need to tune ddev list -j --continuous to get the performance we need. I played around with the heartbeat in the app and scaled it down to 10s and it was no impact to a spike to ~ 20 every 10secs. Then tested at 5 and it made very little difference. So scaled it back until it was still under ddev list -j --continuous which stables out between 70-80 with some spikes over 140 once in awhile.

Example ddev list -j --continuous: https://www.dropbox.com/s/t21tsct2nfcfddu/DDEV-List-Continuous.mov?dl=0

Tuning the heartbeat: https://www.dropbox.com/s/h6gvospexrbyeio/DDEV-2s.mov?dl=0 https://www.dropbox.com/s/qud9zlvxi6m3z27/DDEV-3s.mov?dl=0

Deep Dive: https://www.dropbox.com/s/y594xs7jgysq316/DDEV-DeepDive.mov?dl=0

[alkymst]

https://github.com/drud/ddev-ui/pull/117