docker / docker/cli

stack deploy should cache image hashes for duration of deploy

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#837 1 comment 0 reactions 0 assignees View on GitHub

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area/stack area/swarm kind/enhancement
Dominant language
Go
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Forks
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Avg merge
1d 15h
Merged PRs (30d)
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Description

When running docker stack deploy, each service defined with an image that uses a :latest tag is going to have to poll the registry to determine if a newer image exists or not.

During the scope of a single deploy, wouldn't it make more sense to cache the image hashes to avoid unnecessary http calls for subsequent services that use the same image:tag?

If using --resolve-image=never is any indication, this could greatly speed up deploy runs on stacks with large numbers of services that use the same image. (Understanding that using :latest is usually not a best practice)

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Research direction

Start at the docker stack deploy image-resolution path and trace how services using :latest query the registry during one deploy. Check the existing stack deploy tests and determine how repeated image:tag lookups are handled. Done means a single deploy avoids duplicate registry calls for the same image:tag without changing image-resolution behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
docker, go
Domain
cli, devops
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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