[Feature Request] Group requests based on image/repo

[mlofjard]

If I have 7 containers running the same image from the same repo, WUD currently makes at minimum 7 requests to the repo when fetching tags.
Grouping these fetches based on image and repo would result in fewer request made.

Thoughts? I might PR this if there aren't any obvious problems with it.

[fmartinou]

Hi, thanks for the proposal; it makes sense to try to reduce the number of calls to external registries 👍 .

But it's probably not as easy to do 😃 .

Due to the current implementation of wud, it should be feasible to group those calls for identical images deployed on the same Docker host.
Being able to group calls for identical images deployed to multiple Docker hosts will be complicated (because each host is watched independently).

Let's also notice that "identical containers eligible for grouping" means:

• same registry
• same image
• same tag
• same wud labels (include, exclude...)

If you want to try to implement it; please (I'll help you)!

[mlofjard]

Regarding the current tags and include/exclude/transform labels, my plan was to separate the fetching from the tag processing, so that the flow would be something like this:

1. A watcher starts watching (by cron or manual)
2. All containers for that that watcher is grouped by registry and image.
3. From the grouped list, all tags are fetched and put in a temporary cache-object
4. From the ungrouped list, all containers are processed (a copy of the tag-list for that container is filtered, transformed, and semver compared)