Fixed broken unit test
Revert "Removed unnecessary property on the sequential data loader"

This reverts commit ac512387b3545621104879f308c9bb8fcaec5d35.
Revert "Prevent send task from swallowing exception"

This reverts commit 91d155f331246dce2ba4f46cba593cfd2b8dff3b.
Making expire time atomic long on sequential data loader