In blue-green deployments, the current version of the application service, called blue, handles all the application traffic. We then install the new version of the application service, called green, on the production system. The new service is not wired with the rest of the application yet.
Once green is installed, we can execute smoke tests against this new service and, if those succeed, the router can be configured to funnel all traffic that previously went to blue to the new service, green. The behavior of green is then observed closely and, if all success criteria are met, blue can be decommissioned. But if, for some reason, green shows some unexpected or unwanted behavior, the router can be reconfigured to return ...
