There is an issue with the GORM auto-migration, in that it doesn't
always disable foreign key constraints when it should. Due to
limitations of SQLite, not all 'alter table' commands you'd want to use
are available. As a workaround, these steps are performed:
1. create a new table with the desired schema,
2. copy the data over,
3. drop the old table,
4. rename the new table to the old name.
Step #3 will wreak havoc with the database when foreign key constraint
checks are active, so no we temporarily deactivate them while performing
database migration.
Perform these two SQL calls & check their result:
- `PRAGMA integrity_check`
- `PRAGMA foreign_key_check`:
See https: //www.sqlite.org/pragma.html for more info on these.
This also removes the unused `PeriodicMaintenanceLoop()` function.
Periodic checking while Flamenco Manager is running might be introduced
in a future commit, after the startup-time checks have been shown to not
get in the way.
When there is an error detected at startup, close the database connection.
Before, the connection could be kept open even when an error was returned,
causing the write-ahead log files to be kept around. These are now
properly integrated into the main database file before exiting.
Run `PRAGMA journal_mode = WAL` and `PRAGMA synchronous = normal` when
connecting to the SQLite database. This enables the write-ahead-log journal
mode, which makes it safe to enable "normal" synchronisation (instead of
the default "full" synchronisation).
`persistence.Model` contains the common database fields for most model
structs. It is a copy of `gorm.Model`, but without the `DeletedAt`
field (which triggers Gorm's soft deletion).
Soft deletion is not used by Flamenco. If it ever becomes necessary to
support soft-deletion, see https://gorm.io/docs/delete.html#Soft-Delete
SQLite can return `SQLITE_BUSY` errors when it's doing too many things at
the same time. This is now improved a bit by setting a 5-second timeout,
during which the SQLite driver will wait for the database to become
available. If that doesn't happen, Flamenco Manager will return a
`503 Service Unavailable` response so that the client knows to back off
a little.
The add-on code was copy-pasted from other addons and used the GPL v2
license, whereas by accident the LICENSE text file had the GNU "Affero" GPL
license v3 (instead of regular GPL v3).
This is now all streamlined, and all code is licensed as "GPL v3 or later".
Furthermore, the code comments just show a SPDX License Identifier
instead of an entire license block.
