Control concurrent instance starts in cf push --strategy rolling

[mayrstefan]

What's the user value of this feature request? Speed up deployment of apps with many instances and/or slow startup times

Who is the functionality for? Improvement of cf push rolling update strategy

How often will this functionality be used by the user? Less often for small fast starting apps with small instance counts, more often for slow starting apps with high instance counts

Who else is affected by the change? Nobody should be affected. The default can stay with one concurrent revision deployment

Is your feature request related to a problem? Please describe. Before cf CLI v7 we used a blue-green deployment which starts all app instances concurrently and swapped routes afterwards. Changing them to cf push --strategy rolling increased deployment time from 2 minutes to 8 minutes which causes the CI/CD system to fail (timeout after 6 minutes). Developers want to stay with the old deployment method instead of migrating to the new one.

Describe the solution you'd like Add a parameter, e.g. --max-inflight, to control how man app instances of the new revision are concurrently started. Default can be 1to keep the current behaviour

Describe alternatives you've considered Use a plugin or a helper script for blue-green deployment

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/175787191

The labels on this github issue will be updated when the story is started.