What are .recommenders and .metadata in Eclipse workspace and should they be in sync between devices?

Question

To work seamlessly on different Windows 10 devices, I added an Eclipse workspace to OneDrive (OneDrive/Eclipse). The contents of this folder are my projects, and a .metadata (~45MB) folder, and a (hidden?) .recommenders (~5MB) folder.

Because all of this is inside OneDrive, all files and projects get synced between devices. If I come home from work, the projects will sync to my home computer, but so will the .metadata and .recommenders folders.

The problem is that OneDrive often runs into issues: something cannot be synced or overwritten, so it creates a local copy - which is obviously annoying. Upon closer inspections I realised I don't even know what .metadata and .recommenders are, or what they do.

1. Should these folders be device specific and should hence not be syncronised between devices OR are they workspace specific and are they required to be in sync?
2. What do these folders actually contain? When going through some files I see a lot of folders, plug-ins, and preferences but I don't get what they are for.

Answer 1

To what extend do you want it to be seamless? Including workspace settings or not?

• .recommenders should contain information about dynamic ctrl-space completion based on the user's past behavior etc. Probably not needed for a seamless experience unless you care about details.
• .metadata is all the workspace settings & cache & essentially the workspace's home directory. It contains all sorts of things: What is the .metadata folder in Eclipse workspace? Not super important to sync if you enable per project settings instead of workspace settings. But maybe needed for whatever your definition of seamless is. There is lots of caching and other things in there that isn't useful to sync and can cause odd effects so I would rather avoid the entire folder.