Databases

Databases

The ToMaTo backend needs a database to store information about hosts, topologies and users. The choice of this database is important for the performance of the ToMaTo backend.

ToMaTo uses Django as a database backend so the Django database documentation applies to ToMaTo as well.

SQLite

SQLite can be used as a database backend for very small setups or for testing. Since ToMaTo features long-running transactions the TIMEOUT parameter mentioned in the Django documentation should be increased to avoid "database is locked" errors.

Note that SQLite lacks some features of real databases and thus is not suitable for developing ToMaTo.

PostgreSQL

PostgreSQL is the database that is used in the German-Lab installation. It is a full-featured database with good performance.

Raising the connection limit

The default database connection limit of PostgreSQL is set to 100 which can be reached by ToMaTo if several users are running a lot tasks in parallel. In the config file postgresql.conf the value max_connections can be raised to allow more concurrent connections. If the postgres server then hits the shared memory limit, the sysctl value kernel.shmmax needs to be increased. (See the PostgreSQl documentation for more details.)

Exporting and importing the ToMaTo data

The manage.py script that comes with the ToMaTo backend can be used to dump and load the database contents in a generic database-agnostic format. These commands might only work when run as user tomato, so sudo -u tomato ./manage.py .... Also note that the commands only work when the database is up-to-date with the current layout in the code. (See migration for details)

Dumping the database

The following command dumps the database to a file named "dump.json" in the current directory:

$ ./manage.py dumpdata tomato south > dump.json

Loading the data into the database

The following command load a dump from a file named "dump.json" into the database. (Note that the file extension must be skipped in this command)

$ ./manage.py loaddata dump

Database migrations

As the database layout of ToMaTo changes, the database must be migrated to the new layout. ToMaTo automatically migrates old database schemas to the newest one. (Backups should still be made before the migration.)