[Fleet] Add error handling: uploaded package missing from in-memory cache

[skh]

Currently, when Kibana is restarted, all packages are gone from the in-memory cache, so further operations that need access to package content will potentially fail, even if the package assets (dashboards, visualizations, pipelines, mappings etc.) are still safely installed.

For registry packages, there is ensureCachedArchiveInfo() that re-fetches the package from the registry and re-fills the in-memory cache whenever necessary.

For uploaded packages, we need a strategy how to handle this case

• Uninstall uploaded packages and log a warning about this during /setup?
• Show a warning in the UI when uploaded packages with missing sources are detected?
• Log a warning whenever an operation fails to access a package file and hope for the best?

This problem will be less urgent once we store all packages in a dedicated ES index (see #81110 ). It can still happen when the package storage index disappears, is accidentally deleted, wasn’t included in a backup etc.

[elasticmachine]

Pinging @elastic/ingest-management (Feature:Fleet)

[elasticmachine]

Pinging @elastic/ingest-management (Feature:EPM)

[elasticmachine]

Pinging @elastic/ingest-management (Team:Ingest Management)

[ruflin]

@skh Haven't been thinking of your last point so far that even if we store it, the user could "wipe" the storage index. Lets make sure we plan for this.

[kpollich]

The in-memory cache implementation has been iterated on in the last few years, and I don't believe this relevant any longer. Package info objects and archive file listings are added to the cache as each package is requested or installed. Wiping out the in-memory cache on reboot does not appear to have any ill effects on Kibana/Fleet functionality at this time.