Consider current log file size for rotating

[gerasym]

Feature Request

Consider current log file size for rotating

Proposal:

It would be better to set https://github.com/influxdata/telegraf/blob/master/internal/rotate/file_writer.go#L109 to current file size

Current behavior:

Logfile is rotated only when bytesWritten reaches logfile_rotation_max_size, which means if telegraf was restarted/crashed logfile will not be rotated.

Desired behavior:

Rotate logfile when it's size exceeds logfile_rotation_max_size

Use case: This is just more reliable

[danielnelson]

This is a duplicate of #6776.