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appc / spec

App Container Specification and Tooling (archived, see https://github.com/rkt/rkt/issues/4024)
Apache License 2.0
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spec: add appData volume type #660

Closed jonboulle closed 7 years ago

jonboulle commented 8 years ago

Add a new volume type, similar to empty but prepopulated with data from the app filesystem, similar to how Docker volumes work.

@lucab wdyt?

euank commented 8 years ago

Sounds like a sane thing to have to me.

I'm slightly iffy on the name because it implies the use of a copy-up filesystem, which really is an implementation detail. Maybe something like 'appData' or 'existingData'? Neither of those seem particularly better tan copyUp to me though, and I'm fine with copyUp too.

lucab commented 8 years ago

rkt have a usecase for this (mostly for interoperability), so thanks for adding it. I'm not much into bikeshedding here, so feel free to pick the name you prefer. (If you actually need a tie-breaker, appData sounds like the most obvious keyword to me)

squeed commented 8 years ago

What happens if multiple apps in the pod mount the volume and have data to initialize?

We may need to declare this as a MountPoint option as well.

jonboulle commented 8 years ago

Renamed to appData

jonboulle commented 8 years ago

@squeed can you take this over?

squeed commented 8 years ago

Hyup.

jonboulle commented 8 years ago

@squeed bump?

squeed commented 8 years ago

@jonboulle any thoughts on the ordering semantics?

jonboulle commented 8 years ago

@squeed honestly I'd lean towards saying that's unspecified and discouraged behaviour. Is there a sensible usecase for something more controlled?

lucab commented 8 years ago

As much as I don't like UB, I think this is probably one of those cases where it has to be. At best, this is related to application add/start ordering inside a both. Do we say explicitly say anything about that somewhere else in the spec? In that case, we could just refer to it.

jonboulle commented 7 years ago

branch is at https://github.com/jonboulle/spec/tree/volthiing