SaaSy maps - using django-tenants and geodjango to provide web-gis software-as-a-service

SAASY MAPS - USING DJANGO-
TENANTS AND GEODJANGO TO
PROVIDE WEB-GIS SOFTWARE-AS-A-
SERVICE
Anusha Chickermane

OBJECTIVES
• create a semi-isolated multi-tenant architecture using django-
tenants+postgresql
• build on top of it using geodjango+postgis+openlayers to provide
individualised web mapping services to different clients
• performance and security implications of this approach
• We achieve this by creating a website that shows accident point locations
for three different counties and brings up the associated attributes of
date_of_accident and number_of_vehicles
• Code and this presentation at https://github.com/anushamc/foss4guk-
django-tenants

SOFTWARE AS A SERVICE
• SaaS - software deployment
model where applications are
remotely hosted by the service
provider and made available to
customers on demand
• Eg. github.io, has multiple tenants
• tombatossals.github.io/angular-
openlayers-directive/ – user tombatossals
example page
• blueimp.github.io/jQuery-File-Upload/ -
user bluimp’s example page
• We look at the top 2 layers of the SaaS
architecture – Saas apps and
Application services

SAAS SECURITY CONCERNS
• SaaS deployment model – Aws or self-hosted?
• Data security(encryption, app vulnerability) – Django+postgres
• Network security (SSL) – Django
• Regulatory compliance
• Data segregation – tenant-schemas
• Availability
• Backup
• Identity management and sign-on process - Django

DATA SEGRATION
• django-tenants lies in the
middle: shared database,
separate schemas
• Isolated – more secure, but
costlier to implement and
maintain, and lower
performance
• Shared – less secure, but
easier to implement and
better performance
• The right choice on the
spectrum depends on
business requirements and
sensitivity of the data

PERFORMANCE
• Not as memory intensive as having separate databases
• As the number of schemas (i.e. tenants) grows, propagating model
(i.e. database structure)changes will take longer – parallel migrations
help reduce this performance hit
• Since the same database models are used across tenants,
customisation of each tenant is limited to only changing the look &
feel via templates – i.e cant have one geometry field for one tenant
and two for another in the same model
• If using main-domain and subdomain, eg github.io and
bluimp.github.io, need to watch out for cookie attacks across
subdomains

THE DJANGO FRAMEWORK
• MVT – Model View Template
• Model – defines the data
structure and handles the
database queries
• View – determines what data
from the model should be
returned in HTTP response
• Template – renders data in
HTML(or JSON or XML) and
makes it look pretty

A TYPICAL DJANGO PROJECT
• mysite/
• manage.py
• mysite/
• settings.py
• urls.py
• wsgi.py
• app/
• admin.py
• migrations/
• models.py
• static/
• css/
• js/
• templates/
• Index.html
• tests.py
• views.py
• manage.py – runserver,
makemigrations, migrate
• settings.py – database and site
settings
• urls.py – urls mapped to views
• admin – to create the admin interface
• Models – define the database
structure
• Templates – html files with Django
tags
• Views – handle get and post requests

DJANGO-TENANTS APP
• public_app – accessed from
the main domain i.e.
www.mainsite.com
• tenant_app – accessed from
the tenant’s sub-domain
• mysite/
• manage.py
• mysite/
• settings.py
• …
• public_app/
• admin.py
• migrations/
• …
• tenant_app/
• admin.py
• migrations/
• …

SETUP
• Boot from OS-Geo-Live
• Insert disk into CD drive, restart system and hold down F12 to access boot
options
• For windows 8 and above – Click on the power option (either on the Start
Screen or the Charms Bar) and then hold down the shift key while clicking on
Restart.

MODIFYING THE HOSTS FILE TO
SIMULATE DIFFERENT TENANTS
• Open the terminal and run the following command:
sudo vim /etc/hosts
• Near the top of the file, add the following lines:
127.0.0.1 mainsite.com
127.0.0.1 cumbria.mainsite.com
127.0.0.1 lancashire.mainsite.com
127.0.0.1 london.mainsite.com
• To exit the editor, press ESC and then type :wq

CREATING THE DATABASE
• Open pgAdmin III.
• Create a new database called ‘multi_county_db’.
• Add the postgis extension.

INSTALLING DJANGO, GEODJANGO AND
DJANGO-TENANTS
• Open the terminal and run
• Install pip and django:
sudo apt-get install python3-pip
sudo pip3 install django
• Install python bindings for postgres:
sudo apt-get install python3-psycopg2
• Install Django-tenants:
sudo pip3 install django-tenants

CREATING THE PROJECT
• Create the project
django-admin startproject multi_county
• Open the project and create apps
cd multi_county
python3 manage.py startapp public_app
python3 manage.py startapp tenant_app
• Replace contents of multi_countysettings.py with
https://raw.githubusercontent.com/anushamc/foss4guk-django-
tenants/master/multi_county/multi_county/settings.py
• Replace contents of public_appmodels.py with
tenants/master/multi_county/public_app/models.py

CREATING THE PROJECT
python3 manage.py migrate_schemas –-shared
• Replace contents of tenant_appmodels.py with
https://github.com/anushamc/foss4guk-django-
tenants/blob/master/multi_county/tenant_app/models.py
python3 manage.py makemigrations
python3 manage.py migrate_schemas

CREATING THE TENANTS********
• In the same folder as manage.py, download the file
create_tenants.py from
python3 manage.py shell < create_tenants.py

IMPORTING THE DATA
• Download the data for the schemas from
https://github.com/anushamc/foss4guk-django-
tenants/tree/master/data
• Go to PG Admin III and expand the schemas Lancashire, cumbria
and london
• Right-click the tenant_app_accident table for each county schema,
and select Import…
• In File Options tab, change type to csv and choose the relevant csv file
• In Columns uncheck id and geom
• In Misc. Options check header
• Click Import button
• Do this for all 3 county schemas

IMPORTING THE DATA
• From PG Admin III Run the following sql command on the database:
UPDATE antrim.tenant_app_accident SET geom=ST_GeomFromText('POINT(' ||
location_easting_osgr || ' ' || location_northing_osgr || ')',27700);
UPDATE lancashire.tenant_app_accident SET geom=ST_GeomFromText('POINT(' ||
UPDATE london.tenant_app_accident SET geom=ST_GeomFromText('POINT(' ||

CREATING THE TEMPLATE
• Create a new folder called static in tenant_app folder, and extract into it
javascript-libraries.zip from https://github.com/anushamc/foss4guk-django-
tenants/blob/master/javascript-libraries.zip?raw=true
• Create a new folder called templates in tenant_app folder and place file
index.html from https://raw.githubusercontent.com/anushamc/foss4guk-
django-tenants/master/multi_county/tenant_app/templates/index.html
• Create a new folder called js in tenant_appstatic folder and place file
accidents.js from https://raw.githubusercontent.com/anushamc/foss4guk-
django-tenants/master/multi_county/tenant_app/static/js/accidents.js

CREATING THE TEMPLATE
• Create a new folder called css in tenant_appstatic folder and
place files themes.min.css and accidents.css from
tenants/master/multi_county/tenant_app/static/css/theme.min.css
and https://raw.githubusercontent.com/anushamc/foss4guk-django-
tenants/master/multi_county/tenant_app/static/css/accidents.css

CREATING THE VIEW
• Replace the contents of the tenant_app/views.py file with
tenants/master/multi_county/tenant_app/views.py
• Replace the contents of the multi_county/urls.py file with
tenants/master/multi_county/multi_county/urls.py
python3 manage.py runserver
• Open mainsite.com:8000 to get an empty map,
cumbria.mainsite.com:8000 to get the accidents points layer from Cumbia,
london.mainsite.com:8000 to get London, and
lancashire.mainsite.com:8000 to get the data from Lancaster

SaaSy maps - using django-tenants and geodjango to provide web-gis software-as-a-service

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