Data safety: no silent loss, ever

The worst scenario of a sync tool is a deletion spreading without anyone wanting it: an unplugged disk, a renamed folder, a slip of the hand. HtkCloudSync is built around one rule: syncing never deletes anything permanently, and every heavy decision is asked of you.

The trash, on both sides

A file deleted on the computer is sent to the Google Drive trash, where Google keeps it for thirty days. You can restore it from Google Drive, and empty that trash from HtkCloudSync (see Google Drive trash).
A file deleted in the cloud is sent to your desktop trash, the one of Files, from where you can restore it. If that trash is not available, for instance on a network share, the file is stored in a fallback folder of the application, along with its original location.
HtkCloudSync never empties your desktop trash. The only permanent deletion it can do is emptying the Google Drive trash, at your request and after confirmation.

Conflicts keep both versions

A file changed on both sides is never overwritten: both versions are kept, under two names. See Conflicts.

The mass-deletion threshold

When a single cycle would remove more than 100 files or folders (default value), the service stops before acting: the account moves to “Confirmation required”, and nothing is executed until you have decided. This is what happens after a folder emptied by mistake, an unplugged external disk or a folder moved out of the local folder.

A banner shows the account and the number of deletions, with the Review button; a “Deletions to confirm” notification warns you if they are on.
The “Confirm deletions” question explains the situation: “…. This usually happens after a folder was emptied or disconnected. Deleted files go to the trash on both sides; you can also pause and check first.”
Pause, the default choice, pauses the account so you can check; Apply deletions executes exactly the batch shown, towards the trashes.

Closing the question without choosing changes nothing: the banner stays, and the account waits. If the batch changes while the question is open, the window closes it and explains: “The deletions to confirm have changed: please review them again” or “Nothing left to confirm: the pending deletions are obsolete”. A confirmation only covers the batch shown, once.

The threshold is set in “Settings”, line “Ask before deleting more than”; at 0, every deletion asks for confirmation. Excluding folders from the “Folders” page has its own confirmation and only allows the corresponding deletions.

The local folder missing or emptied

If the local folder no longer exists, cannot be read, or emptied all at once (disk not mounted, folder renamed), the service refuses to conclude that you deleted everything: the account moves to “Error” with the explanation on the “Status” line of the “Accounts” page, and no deletion is propagated to the cloud. Plug the disk back or put the folder back, then click Sync now: everything resumes. A subfolder that cannot be read for a moment is simply left aside for the cycle.

Restorations

A file deleted on one side but changed on the other since the last sync is not deleted: it is restored. A folder deleted on the computer but which received new files in the cloud is recreated. In doubt, HtkCloudSync keeps.

When space runs out

When Google refuses an upload because your Drive is full, or when your disk is full during a download, the transfers concerned are put on hold, not abandoned. The account moves to “Attention required”, the “Status” line says what is waiting and how much, and the other transfers go on. The service retries at growing intervals, from one minute up to one hour, and as soon as it sees space freed. The tooltip of the overall status sums up what to do: “Free up space (cloud or disk): waiting transfers resume on their own.” A “Sync is waiting for free space” notification warns you once per episode.

What is not synced

Symbolic links and special files are left as they are: neither sent nor taken for deletions. Files matching the “Ignored files” patterns are neither sent, nor downloaded, nor sent to the trash.

Your data

HtkCloudSync collects nothing: your files only travel between your computer and your Google account, over an encrypted connection. HTKapp has no intermediate server.
Once a day, as soon as an account is connected, the service asks htkapp.com which version is the latest published one. This request carries no identifier, no information about your accounts or files, and not even the installed version: the comparison happens on your computer. The server sees the computer's IP address, as for any web page. The “Check for updates” setting turns it off.
Your sign-in to Google is kept in the keyring of your session, never in a plain file. If the keyring cannot be reached, the account shows “Sign-in required” rather than saving anything elsewhere.
Disconnecting an account erases that sign-in from the computer; the permission on Google's side is revoked from the connected applications of your Google account.
The service's log and the export of the “Activity” page contain paths, sizes and messages, never the content of your files nor your sign-in.