* fix potential problem
Signed-off-by: Nyhmo <yihua.mo@zilliz.com>

* insert buffer full trigger flush
Signed-off-by: Nyhmo <yihua.mo@zilliz.com>

* cleanup files if no collection flushed
Signed-off-by: Nyhmo <yihua.mo@zilliz.com>

* typo
Signed-off-by: Nyhmo <yihua.mo@zilliz.com>

* format
Signed-off-by: Nyhmo <yihua.mo@zilliz.com>
Co-authored-by: NJin Hai <hai.jin@zilliz.com>