Connector Concepts

The framework to develop connectors is decoupled in small pieces of codes interacting together. Each of them can be used or not in an implementation.

An example of implementation is the OpenERP Magento Connector.

This document describes them from a high-level point of view and gives pointers to more concrete ‘how-to’ or small tutorials.

Events

Events are hooks in OpenERP on which we can plug some actions. They are based on an Observer pattern.

The basic idea is to declare an Event, for instance on_record_create. Then each connector has the ability to subscribe one or many function on it. The creation of a record should fire on_record_create, which will trigger all the subscribed functions.

The same event can be shared across several connectors, easing their implementation. For instance, the module connector_ecommerce which extends the framework with common e-commerce capabilities, adds its own events common to e-commerce.

A connectors developer is mostly interested by:

Jobs Queue

This section summarises the Job’s Queue, which articulates around several classes, in broad terms, Job are executed by a Worker which stores them in a JobsQueue.

Jobs are stored in the QueueJob model.

Workers are stored in the QueueWorker model. A WorkerWatcher create or destroy new workers when new Registry are created or destroyed, and signal the aliveness of the workers.

Jobs are assigned to a worker in the database by a cron. The worker loads all the jobs assigned to itself in memory in the JobsQueue. When a worker is dead, it is removed from the database, so the jobs are freeed from the worker and can be assigned to another one.

When multiple OpenERP processes are running, a worker per process is running, but only those which are CronWorkers enqueue and execute jobs, to avoid to clutter the HTTP processes.

A connectors developer is mostly interested by:

  • Delay a job (see the decorator job())

Session

A ConnectorSession is a container for the usual cr, uid, context used in OpenERP. We use them accross the connectors.

Backend

A Backend is a reference to an external system or service.

A backend is defined by a name and a version. For instance Magento 1.7.

A reference can have a parent. The instance Magento 1.7 is the child of Magento.

ConnectorUnit classes are registered on the backends. Then, we are able to ask a registered class to a backend. If no class is found, it will search in its parent backend.

It is always accompanied by a concrete subclass of the model connector_backend.

A connectors developer is mostly interested by:

Environment

An Environment is the scope from which we will do synchronizations.

It contains a Backend, a record of a concrete subclass of the model connector_backend, a Session and the name of the model to work with.

A connectors developer is mostly interested by:

ConnectorUnit

ConnectorUnit are pluggable classes used for the synchronizations with the external systems.

The connector defines some base classes, which you can find below. Note that you can define your own ConnectorUnits as well.

Mappings

The base class is connector.unit.mapper.Mapper.

A mapping translates an external record to an OpenERP record and conversely.

It supports:

direct mappings
Fields a is written in field b.
method mappings
A method is used to convert one or many fields to one or many fields, with transformation. It can be filtered, for example only applied when the record is created or when the source fields are modified.
submapping
a sub-record (lines of a sale order) is converted using another Mapper

Synchronizers

The base class is connector.unit.synchronizer.Synchronizer.

A synchronizer defines the flow of a synchronization with a backend. It can be a record’s import or export, a deletion of something, or anything else. For instance, it will use the mappings to convert the data between both systems, the backend adapters to read or write data on the backend and the binders to create the link between them.

Backend Adapters

The base class is connector.unit.backend_adapter.BackendAdapter.

An external adapter has a common interface to speak with the backend. It translates the basic orders (search, read, write) to the protocol used by the backend.

Binders

The base class is connector.connector.Binder.

Binders are classes which know how to find the external ID for an OpenERP ID, how to find the OpenERP ID for an external ID and how to create the binding between them.

Bindings

Here a binding means the link of a record between OpenERP and a backend.

The proposed implementation for the connectors widely use the _inherits capabilities.

Say we import a customer from Magento.

We create a magento.res.partner model, which _inherits res.partner.

This model, called a binding model, knows the ID of the partner in OpenERP, the ID in Magento and the relation to the backend model.

It also stores all the necessary metadata related to this customer coming from Magento.

Checkpoint

A checkpoint is a record in the model connector.checkpoint linked to a model and a record, the connectors can create a new one when the user needs to review imported documents.