CODEWITHSUNDEEP
scalalift
Paul J
Paul J

Reputation: 777

Upgrading an app running on Lift Framework?

I've recently discovered the lift framework and have read that it's stateful.

Therefore, if I had a high-traffic site running on Lift - say something that was running a chat application that required users to be logged in - and I wanted to upgrade my app, would doing so kick everyone out of chat and make them have to log in again?

Upvotes: 3

Views: 178

Answers (2)

timothy
timothy

Reputation: 497

None of the previous answers are correct. Many of the artefacts held within the LiftSession are non-serilizable, so cant be stuffed into a database. You have two options for doing rollig upgrades of stateful applications:

1) Session bleeding. Basically you ween one of the deployments sessions away until their sessions have ended or X duration passes and then you remove the app from production whilst automatically rerouting traffic to another instance of Lift. Google around for rolling upgrades using HAProxy as this should help you from the cluster perspective.

2) If your state is fairly trivial (mostly primitive-style types: ints, strings etc) then you could think about using ContainerVar/MigratableSession and clustering the state using terracotta or similar. This comes with a range of limits though because it then uses the HTTPSession rather than LiftSession.

You might want to checkout chapter 15 of Lift in Action which details that latter solution in a fair amount of detail.

Upvotes: 2

Kim Stebel
Kim Stebel

Reputation: 42047

If you keep your state in memory and redeploy the web application, that state will be lost. You could save it to a database or a file before redeploying though and read it back from there.

Upvotes: 1

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