backups of project

When backups of the data are taken, how many are kept, and where the archive of every change lies.

Value

{ every, keep, beforeChanges, test, archive, store }. Left out, one is taken each day and before a table change, seven are kept, each is test-restored, and every change is archived beside them.

• archive: false turns the archive off. With it on, the engine keeps every committed change of every data file, in order, cut into parts of limits.archivePart (4 MB), each named by the number of its first change and its time. It reaches back as far as the oldest backup that is kept, and it is what tent data restore --at reads. It holds the record of each change as the store wrote it, so a sealed value stands in it sealed, and it holds no secret. Beside the record it holds only what undo needs and the record does not give: who made the change, and of each row of the app its id, what a row that was set held before, and a row that was removed as it was.
• store: a store of files, s3(...), in which the archive lies, with a copy of every backup beside it, so that a lost disk keeps both. Left out, the archive lies in backups/archive/ of the data folder.

Each change is added to the file of the part that is open, backups/archive/open.part, as it comes, so a stop of the program loses nothing that reached it. A part is closed and sent once it is full and when the app is closed, and a part that a stop left open is sent when the app opens again, with the changes it holds whole: a change that the stop cut off in the middle never reached it. A write whose change a stop caught between its commit and the archive never reached it: when the app opens and holds writes past the last change of the archive, the engine takes a backup at once and writes that gap into the archive's list. A restore to a moment in the gap, and an undo that reaches into it, is refused with code.T0009, which names it; a moment before it, and after that backup, is reached. A person's removal reaches the archive as it reaches the backups: the parts and the backups made before still hold the person until they age out.

Example

export const shop = project('shop', {
  backups: {
    every: '1 day',
    keep: 14,
    store: s3({ url: 'https://storage.example.com', bucket: 'shop-backups', key: secret('STORE_KEY') }),
  },
})

See also

word.project, word.s3, command.data, option.project.limits