Friday, November 2, 2012

Pushing data into OpenERP

The PushSQL module allows external apps to export data to OpenERP properly (through the ORM) just by using INSERT SQL statements.

The motivation for this came from a project where an ETL service was responsible for handling synchronization of data (such as departments, customers and contracts) across several databases and applications.

The ETL tool didn't have a simple way to make XML-RPC calls, and writing directly to OpenERP's tables is not a good solution.

This was solved using a relatively simple "hybrid" solution. The PushSQL module provides a database table for external apps to write data to imported to OpenERP, using plain SQL INSERT statements. A scheduled job regularly looks for new rows in this table and processes them, making the intended changes to OpenERP data.

The table , import_pushsql, has two mandatory columns: model and data. The first is the target model, such as res.partner. The second contains the data to import, using the format for CSV files, but using TAB instead of comma as the column separator.

For example, using PSQL:
INSERT INTO import_pushsql (model, data) VALUES ('res.partner', E'id\tname\tref\nres_partner_XXX\tDemo Customer\tXXX'

Or, if using SQL Server:
INSERT INTO import_pushsql (model, data) VALUES ('res.partner',
'id' +char(9)+ 'name' +char(9)+ 'ref' +char(10)+ 'res_partner_XXX' +char(9)+ 'Demo Customer' +char(9)+ 'XXX'

The scheduled action uses this to run a standard import_data ORM method,  writes the result into the log column, and changes the state to 'done' if successful, or 'cancel' if an error was found.

Compared to the "pull" approach used by the import_odbc module, this "push" approach can provide a few advantages:
  •  No need to install other database clients and middleware in OpenERP's server.
  • It uses less resources on OpenERP server, because there is no need to connect to other servers.
  • Event driven data sync, where an action in another system immediately triggers a write on OpenERP that can be processed within a few minutes.
There is also an obvious disadvantage: the process exporting the data does not have an immediate visibility on the outcome of the OpenERP transaction . There are ways to provide this feedback, but it's not immediate.

Overall, the PushSQL module can provide a very simple and straighforward way for business apps to safely send data to OpenERP, in scenarios where using the API is not an option or would be too cumbersome.

The import_pushsql can be downloaded either from OpenERP Apps or from Launchpad using: bzr branch lp:reis-openerp-addons