Feature Request: Local cache for registry lookups/checks

[KeithB]

Configuration WUD has watchers configured for a number of hosts the the containers running on them. Between base setup (e.g. telegraf) and things running on multiple hosts either for redundancy (e.g. nginx) or just configuration (e.g.syncthing), there are quite a few containers running across the environment that are all against the same base image.

Feature Request Introduction of a local cache to limit calls to registries in this situation. Essentially lookup and analysis would be against the cache with the cache having responsibility for populating either because the data has expired, it wasn't there or something in the config says to not rely on cached data.

Thoughts on functional configuration:

• Expiry time for information in the cache. Default to 24 hours?
• Per watcher config on whether to use the cache or not.
• Per registry config on whether to cache that registries information or not.

I'm sure it's not as simple as that but just putting the feature request out there.

[fmartinou]

This is an interesting proposal; I will think about it.

The most complicated part will likely be to design the cache refresh strategy :thinking: