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634870 (1) [Avatar] Offline
#1
Is the blue/green deployment described in 9.1.2 Atomic and no down-time?
What are the implications/risk for the users of the application?

Aldo
Marko Lukša (70) [Avatar] Offline
#2
It's not atomic, because the actual switch from one set of pods to the other is performed on every worker node separately (the kube-proxy running on that node modifies the iptables rules that direct traffic for the service). There's no synchronization between the kube-proxies (in this or any other case).

As for downtime, existing connections will remain connected to the old version of the pods, while new connections will go to the new pods, which you run before switching the service. This means there should be no broken connections, as long as you keep the old version running until all the existing connections are closed.

A more in-depth explanation of how connections through the kube-proxy work is in one of the later chapters (but not specifically for blue-green deployments).