flask-tenants 0.5.1

A Flask extension for multi-tenancy support

Flask Tenants

Flask Tenants is a Flask extension for multi-tenancy support using subdomains and SQLAlchemy schemas. The MultiTenancyMiddleware extracts the tenant from the request host and switches the database schema accordingly. If no tenant is extracted, it defaults to the public schema.

Installation

pip install flask-tenants

Database Preparation

1. Create a new PostgreSQL database (if not already created):

CREATE DATABASE flask_tenants;

1. Connect to the database and create the public schema and extension for UUID generation:

\c flask_tenants
CREATE SCHEMA IF NOT EXISTS public;

1. Ensure your database user has the necessary privileges to create schemas:

GRANT ALL PRIVILEGES ON DATABASE "flask_tenants" to your_user;

Usage

Basic Setup

Create a Flask application and initialize SQLAlchemy. Set up the multi-tenancy middleware.

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_tenants import FlaskTenants, db
from public.models import Tenant, Domain


app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://user:password@localhost/dbname'
db = SQLAlchemy(app)

# Initialize Flask-Tenants
flask_tenants = FlaskTenants(app, tenant_model=Tenant, domain_model=Domain, db=db, tenant_url_prefix='/_tenant')
flask_tenants.init()

tenant_url_prefix

This is optional, but the default is quite long. It is recommended to set this to a default value that will not be used in any other route. The module uses this on the backend to route tenant-scoped requests and handles it invisibly to prevent the need for a /tenant/ route prefixing all tenant-scoped requests.

Models

Tenancy models

Define your tenant and domain models by inheriting from BaseTenant and BaseDomain.

from flask_tenants import BaseTenant, BaseDomain, db

class Tenant(BaseTenant):
    __tablename__ = 'tenants'
    phone_number = db.Column(db.String(20), nullable=True)
    address = db.Column(db.String(255), nullable=True)
    deactivated = db.Column(db.Boolean(), nullable=False, default=False)

class Domain(BaseDomain):
    __tablename__ = 'domains'
    tenant_id = db.Column(db.Integer, db.ForeignKey('tenants.id'), nullable=False)
    tenant_name = db.Column(db.String(128), nullable=False)
    domain_name = db.Column(db.String(255), unique=True, nullable=False)
    is_primary = db.Column(db.Boolean, default=False, nullable=False)

BaseTenant

BaseTenant provides name, created_at, and updated_at attributes.

class BaseTenant(db.Model):
    __abstract__ = True
    id = db.Column(db.Integer, primary_key=True, autoincrement=True, unique=True)  # Ensure unique constraint
    name = db.Column(db.String(128), unique=True, nullable=False)
    created_at = db.Column(db.DateTime, nullable=False, default=db.func.current_timestamp())
    updated_at = db.Column(db.DateTime, nullable=False, default=db.func.current_timestamp(),
                           onupdate=db.func.current_timestamp())

BaseDomain

BaseDomain provides tenant_name, domain_name, and is_primary attributes.

class BaseDomain(db.Model):
    __abstract__ = True
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    tenant_name = db.Column(db.String(128), db.ForeignKey('tenants.name'), nullable=False)
    domain_name = db.Column(db.String(255), unique=True, nullable=False)
    is_primary = db.Column(db.Boolean, default=False, nullable=False)

Tenant Deactivation

If you'd like to be able to deactivate a tenant without deleting it, for example if a SaaS customer forgets to pay their bill, you can optionally add a deactivated field to your tenant model:

class Tenant(BaseTenant):
    __tablename__ = 'tenants'
    # ...
    deactivated = db.Column(db.Boolean(), nullable=False, default=False)

Flask-Tenants will check if this field exists early in the request lifecycle and abort the request early with a TenantActivationError if it is True.

Error Handling

Flask-Tenants middleware raises two custom exceptions that need to be handled by the end developer. Namely, TenantActivationError (if deactivated is utilized in Tenant model) and TenantNotFoundError. These can be handled in a custom errors.py file, as shown:

from flask import jsonify
from flask_tenants.exceptions import TenantNotFoundError, TenantActivationError


def register_error_handlers(app):
    @app.errorhandler(TenantNotFoundError)
    def handle_tenant_not_found(error):
        response = jsonify({
            'error': 'TenantNotFoundError',
            'message': 'The requested tenant was not found.'
        })
        response.status_code = 404
        return response

    @app.errorhandler(TenantActivationError)
    def handle_tenant_activation_error(error):
        response = jsonify({
            'error': 'TenantActivationError',
            'message': 'The requested tenant is deactivated.'
        })
        response.status_code = 403
        return response

Additionally, in app.py:

def create_app():
    app = Flask(__name__)
    app.config.from_object(Config)

    # Register error handlers
    register_error_handlers(app)

    # Initialize Flask Tenants
    flask_tenants = FlaskTenants(app, tenant_model=Tenant, domain_model=Domain, db=db, tenant_url_prefix='/_tenant')
    ...

Here is the full list of custom exceptions provided by the Flask-Tenants module:

• SchemaCreationError
• SchemaAlreadyExistsError
• SchemaDoesNotExistError
• SchemaRenameError
• SchemaDropError
• TableCreationError
• TenantActivationError
• TenantNotFoundError

Tenant scoped models

Define tenant scoped models by inheriting from BaseTenantModel and setting the proper info table argument.

from flask_tenants.models import db, BaseTenantModel


class Tank(BaseTenantModel):
    __abstract__ = False
    __tablename__ = 'tanks'
    __table_args__ = {'info': {'tenant_specific': True}}
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    name = db.Column(db.String(128), nullable=True)
    capacity = db.Column(db.Float, nullable=True)
    location = db.Column(db.String(255), nullable=True)

BaseTenantModel

BaseTenantModel provides no attributes.

class BaseTenantModel(db.Model):
    __abstract__ = True
    __table_args__ = ({'schema': 'tenant'})

Implementing CRUD Operations

The g.db_session object must be used for all database accesses for search_path schema to automatically apply.

from flask import g

tanks = g.db_session.query(Tank).all()

Example and Demos

You can find an example multi-tenant blog application at this repo