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What is parallelism?

Hi All, new docker user here. Can someone please explain what the --parallelism option does?

thanks,

Can you provide a context?

example is

docker service update --update-parallelism

It’s the number of replicas updated at the same time, if you mean --update-parallelism. I am not aware of --parallelism itself.

Imagine you have a service with 10 replicas: then it would update 2 service, then the next 2 and so on. This way you only have 2 replicas unavailable during the update.

Imagine you have a service with 2 replicas: then this would make both replicas unavailable at once. Probably something one would not want to happen…

Update: had to remove a terrible typo. couldn’t resist.