Flask extension

Flask extension provides means for easy integration with PostgreSQL-Audit, Flask-Login and Flask-SQLAlchemy. It provides all the goodies that SQLAlchemy integration provides along with:

• By default, the Flask extensions tries to get the current user from Flask-Login and assigns the id of this object as the actor_id of all activities in given transaction. It also assigns the current user’s IP address to all present activities.

• Easy overriding of current activity values using activity_values context manager

from postgresql_audit.flask import versioning_manager

from my_app.extensions import db


versioning_manager.init(db.Model)


class Article(db.Model):
    __tablename__ = 'article'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String)


article = Article(name='Some article')
db.session.add(article)
db.session.commit()

Overriding activity values

In some situations you may want to override the current activity values. One scenario is where you want to track the changes to associated objects and mark those changes with the target_id property of the Activity model.

For example, consider the following model structure with Article and Tag. Let’s say we want to show the changelog of an article that contains all changes to this article and its tags:

from postgresql_audit.flask import versioning_manager

from my_app.extensions import db


versioning_manager.init(db.Model)


class Article(db.Model):
    __tablename__ = 'article'
    __versioned__ = {}
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String)


class Tag(db.Model):
    __tablename__ = 'tag'
    __versioned__ = {}
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String)
    article_id = db.Column(
        db.Integer,
        db.ForeignKey(Article.id, ondelete='CASCADE')
    )
    article = db.relationship(Article, backref='tags')

When tracking the changes to article, we don’t need any changes:

article = Article(name='Some article')
db.session.add(article)
db.session.commit()

When adding tags, we need to make the generated activities use the article id as the target_id so that we can track them later on:

from postgresql_audit.flask import activity_values


with activity_values(target_id=str(article.id)):
    article.tags = [Tag(name='Some tag')]
    db.session.commit()

Now, we can find all activities for an article with the following query:

Activity = versioning_manager.activity_cls

activities = Activity.query.filter(
    db.or_(
        db.and_(
            Activity.target_id == str(article.id),
            Activity.target_table_name == 'article'
        ),
        db.and_(
            db.or_(
                Activity.row_data['id'] == article.id,
                Activity.changed_fields['id'] == article.id
            ),
            Activity.table_name == 'article'
        )
    )
).order_by(Activity.issued_at)

Recording IP address behind proxy

By default PostgreSQL-Audit stores the client address as found in the request and does not attempt to make assumptions on server proxy configuration. Thus, in case the flask app runs after an http server (e.g nginx), and depending on configuration, flask may receive no IP. To overcome this, it is advised to follow flask documentation on proxy setups.