image caching

[joestubbs]

Currently, when the first worker on a given docker host is created for an actor, the actor's image is pulled from the docker hub. If the image has been updated on the hub since the actor was registered, the newer image will be pulled. This might not be desirable.

Instead, we should cache actor images in the abaco system (perhaps, a private docker registry).

[NotChristianGarcia]

I might know a solution here. Rather than creating a private docker registry. It should be possible to, when reading from the actor creation message, to translate images:tags to image@digests. image@digests remain constant so you'll pull the same image even when it's updated.

Tried for a bit to directly get image@digests from dockerhub using image:tag and failed. However worst case, you can pull the image once, and run the following to get the image@digests.

docker inspect --format='{{index .RepoDigests 0}}' $IMAGE

Possible solution, just wanted to comment.

[jlooney]

@NotChristianGarcia I think this is an interesting solution worth trying!