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Kamal Proxy – A minimal HTTP proxy for zero-downtime deployments

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Re: Kamal Proxy – A minimal HTTP proxy for zero-downtime deployments

#21

Post by joeatwork »

thelastparadise wrote: post #16
kh_hk wrote: post #10

I don't understand how to use this, maybe I am missing something. Following the example, it starts 4 replicas of a 'web' service. You can create a service by running a deploy to one of the replicas, let's say example-web-1. What does the other 3 replicas do? Now, let's say I update 'web'. Let's assume I want to do a zero-downtime deployment. That means I should be able to run a build command on the 'web' service, sta…

Why would I not just do k8s rollout restart deployment? Or just switch my DNS or router between two backends?

I think this is part of a lighter weight Kubernetes alternative.

Re: Kamal Proxy – A minimal HTTP proxy for zero-downtime deployments

#22

Post by stephenr »

blue_pants wrote: post #12

Can someone briefly explain how ZDD works in general? I guess both versions of the app must be running simultaneously, with new traffic being routed to the new version of the app. But what about DB migrations? Assuming the app uses a single database, and the new version of the app introduces changes to the DB schema, the new app version would modify the schema during startup via a migration script. However, the previ…

Others have described the how part if you do need truly zero downtime deployments, but I think it's worth pointing out that for most organisations, and most migrations, the amount of downtime due to a db migration is virtually indistinguishable from zero, particularly if you have a regional audience, and can aim for "quiet" hours to perform deployments.

Re: Kamal Proxy – A minimal HTTP proxy for zero-downtime deployments

#25

Post by ianpurton »

joeatwork wrote: post #21
thelastparadise wrote: post #16

Earlier quoted context omitted.

Why would I not just do k8s rollout restart deployment? Or just switch my DNS or router between two backends?

I think this is part of a lighter weight Kubernetes alternative.

Lighter than the existing light weight kubernetes alternatives i.e. k3s :)

Re: Kamal Proxy – A minimal HTTP proxy for zero-downtime deployments

#27

Post by wejick »

ianpurton wrote: post #24

DHH in the past has said "This setup helped us dodge the complexity of Kubernetes" But this looks like somehow a re-invention of what Kubernetes provides. Kubernetes has come a long way in terms of ease of deployment on bare metal.

No downtime deployment is always there long before kube. It does look as simple as ever been, not like kube for sure.

Re: Kamal Proxy – A minimal HTTP proxy for zero-downtime deployments

#29

Post by gsanderson »

blue_pants wrote: post #12

Can someone briefly explain how ZDD works in general? I guess both versions of the app must be running simultaneously, with new traffic being routed to the new version of the app. But what about DB migrations? Assuming the app uses a single database, and the new version of the app introduces changes to the DB schema, the new app version would modify the schema during startup via a migration script. However, the previ…

I haven't tried it but it looks like Xata has come up with a neat solution to DB migrations (at least for postgres). There can be two versions of the app running.

https://xata.io/blog/multi-version-schema-migrations

Re: Kamal Proxy – A minimal HTTP proxy for zero-downtime deployments

#30

Post by diggan »

ianpurton wrote: post #25
joeatwork wrote: post #21

Earlier quoted context omitted.

I think this is part of a lighter weight Kubernetes alternative.

Lighter than the existing light weight kubernetes alternatives i.e. k3s :)

Or, hear me out: Kubernetes alternatives that don't involve any parts of Kubernetes at all :)
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