As part of core operations course materials, I see a slide for "Open an Index" with below content
Be aware that opening an index can take a few seconds or
even a couple of minutes
-The primary shards may need some updates applied
‒ A Lucene index will be opened (can take time), and the
transaction log will be replayed
I have few questions: When we reopen an index, in what scenarios will the primary gets updated( or may need updates) . When we close an index since we would have done synced flush, why will it replay from transaction logs or even if i dont do sysnced flush before closing an index, wouldn't ES flush everything from translog bfr closing an index?