my elasticsearch server crashed after a get query, and then the server recovered, but some doc's _source field lost and some doc's _source field lost for replica shard and some lost at primary shard.
is there any one known what has happened?
my elasticsearch server crashed after a get query
Looks strange. Do you have logs of the server? Can you share them?
some doc's _source field lost
WDYM? That the document is still here but with no _source content? Or that the document does not exist at all?
is there any one known what has happened?
No. You need to share your logs and version at least.