(Optional) enforce of file storage sync via fsync()

[drproktor]

To avoid (or at least reduce) database file corruption on system failures like a hard power off, having means to enforce a storage sync via fsync() would be great.

Background

I am currently using JsonDB on a Raspberry Pi and the database file is stored in an ecryptfs encrypted folder. In this scenario a hard power-off after a write to the JsonDB results in reproducable file corruptions. I.e. when mounted again the database file is corrupt and can't be decrypted by ecryptfs correctly. Since ecryptfs is a stacked filesystem, my explanation is that the OS does some additional buffering here and postpones the actual write to storage longer than it does e.g. when running directly on a Ext4 filesystem.

I already prepared a patch which I would be happy to contribute.