wiki:BluePrint/Synchronisation

Version 12 (modified by Fran Boon, 16 years ago) ( diff )

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This page hosts the detailed specification for the ​Blueprint for the Synchronisation.

We need to be able to support synchronising data between instances:

The UUIDs have already been configured: DeveloperGuidelinesDatabaseSynchronization

We need to extend this by Exporting the tables (CSV is best-supported within Web2Py currently)
"complete database backup/restore with db.export_to_csv_file(..),db.import_from_csv_file(...),
reimporting optionally fixes references without need for uuid"

Initially this can be done using appadmin, but we want to make a user-friendly way of dumping all relevant tables.
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

Export tables as CSV (in Controller): 

def export():
    s=StringIO.StringIO()
    db.export_to_csv_file(s)
    response.headers['Content-Type']='text/csv'
    return s.getvalue()

Import tables at the other end: 

def import_and_sync():
    form=FORM(INPUT(_type='file',_name='data'),INPUT(_type='submit'))
    if form.accepts(request.vars):
        db.import_from_csv_file(form.vars.data.file)
        # for every table
        for table in db.tables:
        # for every uuid, delete all but the most recent
            items=db(db[table].id>0).select(db[table].id,db[table].uuid,orderby=~db[table].modified_on,groupby=db[table].uuid)
            for item in items:
                db((db[table].uuid==item.uuid)&(db[table].id!=item.id)).delete()
    return dict(form=form)

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

other related threads:

There is a simple 1-table example appliance which has the ability to do syncs via XML-RPC:

In S2 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)
);
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