= Blueprint for Synchronisation =

We need to be able to support synchronising data between instances:
 * http://wiki.sahana.lk/doku.php?id=doc:sync:english

All tables have UUID fields: DeveloperGuidelinesDatabaseSynchronization

We can Export the tables - CSV is best-supported within Web2Py currently[[BR]]
"complete database backup/restore with db.export_to_csv_file(..),db.import_from_csv_file(...),[[BR]]
reimporting optionally fixes references without need for uuid"
 * http://groups.google.com/group/web2py/browse_thread/thread/c08d1b05ddda672c
 * http://groups.google.com/group/web2py/browse_thread/thread/be927ccf4d9745d2/637e45ccc2cf2583
 * http://groups.google.com/group/web2py/browse_thread/thread/55d923a51eca2c90

This can be done using appadmin, but we have started work on a user-friendly way of dumping all relevant tables:
 * {{{controllers/default.py}}}
 * {{{views/default/export_data.html}}}
 * {{{views/default/import_data.html}}}

Need clear list of which tables to include:
 * not lookup lists which are the same across sites
  * e.g. !OpenStreetMap/Google Layers (but WMS/SOS Layers Yes. Shapefiles Layers Yes if uploads copied across as well)
 * not site-specific stuff such as system_config, gis_keys, etc

Create an index manually to make the search by uuid faster. 

other related threads:
 * http://groups.google.com/group/web2py/browse_thread/thread/af3f7ad5271a10c6/c5e96141c13a29ad
 * http://groups.google.com/group/web2py/browse_thread/thread/7d639c98b5b8dcd2/c0fe17ccbdd12eb7

There is a simple 1-table example appliance which has the ability to do syncs via XML-RPC:
 * http://mdp.cti.depaul.edu/appliances/default/download/app.source.312926207134.txt


In Sahana2 the record ids are UUIDs built from each instance's 'base_uuid'

There is a sync_instance table:
{{{
CREATE TABLE sync_instance (
    base_uuid VARCHAR(4) NOT NULL, -- Instance id
    owner VARCHAR(100), -- Instance owner's name
    contact TEXT, -- Contact details of the instance owner
    url VARCHAR(100) DEFAULT NULL, -- Server url if exists
    last_update TIMESTAMP NOT NULL, -- Last Time sync with the instance
    sync_count INT DEFAULT 0, -- Number of times synchronized
    PRIMARY KEY(base_uuid)
);
}}}