IndexMamanager getIndexManager(); would be ideal, as it contains the other attributes you mentioned.

I'm not sure what you mean by "It's not possible to compose multiple error handlers into one"

I meant the engine does not offer composition support for multiple error handlers, Index Manager implementors and users need to compose themselves, potentially wrapping the default logging error handler but adding another behaviours. I'd say this is minor though, the important thing is having more feedback about the error.