This document discusses converting Django apps into reusable services. It begins by explaining the typical structure of a Django project with multiple apps. It then discusses some of the challenges with this monolithic structure in terms of reusability, scalability and maintainability. The document proposes converting apps into reusable services with defined contracts for communication. It provides examples of defining API endpoints and authentication. Converting apps to services allows for improved reusability as apps can be developed and updated independently. It also enables better scalability by removing dependencies between apps.

1. Django Apps to Services

2. Craig Kerstiens
@craigkerstiens work at @heroku

3. Django
Project A collection of configuration and apps for a particular Website.
(per Django Project)

4. Django
Project A collection of configuration and apps for a particular Website.
App A web application that does something. I.e. Weblog, Poll, Ticket
system
(per Django Project)

5. Table
Table Table
Table
Table Table
Table
Table
Table
Table
Table
Table Table
Table
Table
Table
Table Table
Table Table
Table

6. Table
Table Table
Table
Table Table
Table
Table
Table
Table
Table
Table Table
Table
Table
Table
Table Table
Table Table
Table

7. Table
Table Table
Table
p
Table Table
Table
p
Table
A
Table
Table
Table
Table Table
Table
Table
Table
Table Table
Table Table
Table

8. Monolithic Monster

9. Monolithic Monster
$ ls mysite
models.py
views.py
forms.py
admin.py

10. Monolithic Monster
$ ls mysite $ wc -l models.py
models.py 2557 models.py
views.py $ wc -l view.spy
forms.py 14241 views.py
admin.py

11. Monolithic Monster
$ ls mysite $ wc -l models.py
models.py 2557 models.py
views.py $ wc -l view.spy
forms.py 14241 views.py
admin.py
http://www.slideshare.net/jacobian/the-best-and-worst-of-django

12. Within Django

13. Within Django
Project

14. Within Django
Project
App
App
App

15. Within Django
Project
Tickets
App
FAQ
App
FaqCreator
App

16. Within Django
cd myproject && find .
manage.py
Project requirements.txt
settings.py
urls.py
./faq/admin.py
./faq/forms.py
Tickets
App ./faq/models.py
./faq/urls.py
./faq/views.py
./faqcreator/admin.py
FAQ
App ./faqcreator/forms.py
./faqcreator/models.py
./faqcreator/urls.py
./faqcreator/views.py
./tickets/admin.py
FaqCreator
App ./tickets/forms.py
./tickets/models.py
./tickets/urls.py
./tickets/views.py

17. Reusability

18. cd myproject && find .
Reusability

19. cd myproject && find .
Reusability
manage.py
requirements.txt
settings.py
urls.py
./faq/admin.py
./faq/forms.py
./faq/models.py
./faq/urls.py
./faq/views.py
./faqcreator/admin.py
./faqcreator/forms.py
./faqcreator/models.py
./faqcreator/urls.py
./faqcreator/views.py
./tickets/admin.py
./tickets/forms.py
./tickets/models.py
./tickets/urls.py
./tickets/views.py

20. cd myproject && find .
Reusability
cd myproject && find .
manage.py
requirements.txt manage.py
settings.py requirements.txt
urls.py settings.py
./faq/admin.py urls.py
-->
./faq/forms.py
./faq/models.py cat myproject/requirements.txt
./faq/urls.py
./faq/views.py faq==0.1
./faqcreator/admin.py faqcreator==0.1
./faqcreator/forms.py tickets==0.1
./faqcreator/models.py
./faqcreator/urls.py
./faqcreator/views.py
./tickets/admin.py
./tickets/forms.py
./tickets/models.py
./tickets/urls.py
./tickets/views.py

22. REUSABILITY means faster features due to DRY
(Don’t Repeat Yourself )

23. REUSABILITY means faster features due to DRY
(Don’t Repeat Yourself )
REUSABILITY does not always mean SCALABILITY
or MAINTAINABILITY

24. Django
Project A collection of configuration and apps for a particular Website.
App A web application that does something. I.e. Weblog, Poll, Ticket
system
(per Django Project)

25. Django
Project A collection of configuration and apps for a particular Website.
App A web application that does something. I.e. Weblog, Poll, Ticket
system
Service Method of communication over the web.
Web APIs allow combination of multiple services

27. Tech imitate Teams
Project Company
Tickets
App Support
FAQ
App Knowledge Base
FaqCreator
App

28. Teams
Support
Knowledge Base

29. Teams Grow
App
Support
App
Knowledge Base

30. Teams Grow
App
Support
App
Knowledge Base
Billing

31. Teams Grow
App
Support Marketing
App
Knowledge Base
Billing

32. Teams Grow
App
Support Marketing API
App
Knowledge Base Analytics Front End
Billing Mobile Social

33. Apps Grow
App
Support Marketing API
p s
App
A p
Knowledge Base Analytics Front End
3 App
Billing Mobile Social

34. Apps Grow
App
Support
p
App
s
Marketing App
API
A p
9
App
Knowledge Base App
Analytics App
Front End
App
Billing App
Mobile App
Social

35. Apps Grow
Support
p s
Marketing API
Ap se
Knowledge Base
9 deb a
Analytics Front End
Billing
C o Mobile Social
1

36. SOA To the Rescue

37. SOA To the Rescue

38. SOA To the Rescue
Photo by Paul Downey (psd on flickr)

39. Service
Defined contract for communicating

40. Service
Defined contract for communicating
$ curl -O $FAQ_API/create/
-X “question=my question source=123”

41. In Python

42. In Python
data = {
‘question’: “my question”,
‘source’: 123
}
requests.POST(os.environ[‘FAQ_API’] + ‘/
create/’, data=data)

43. More than just API

44. More than just API
www.google.com

45. More than just API
www.google.com
mail.google.com

46. More than just API
www.google.com
mail.google.com
calendar.google.com

47. More than just API
www.google.com
mail.google.com
calendar.google.com
..............google.com

48. Types of Services

49. Types of Services
site

50. Types of Services
site
subdomain

51. Types of Services
site
subdomain
API

52. Types of Services
site
subdomain
API
- no auth required

53. Types of Services
site
subdomain
API
- no auth required
- API auth required

54. Types of Services
site
subdomain
API
- no auth required
- API auth required
- user auth required

55. Where to Start
App
Support App
Marketing App
API
App
Knowledge Base App
Analytics App
Front End
App
Billing App
Mobile App
Social

56. Where to Start
App
Support App
Marketing API
App
Knowledge Base Analytics Front End
Billing Mobile App
Social

60. 1 Javascript
Many pages

64. LA POSTA

65. Within Django
cd myproject && find .
manage.py
Project requirements.txt
settings.py
urls.py
./faq/admin.py
./faq/forms.py
Tickets
App ./faq/models.py
./faq/urls.py
./faq/views.py
./faqcreator/admin.py
FAQ
App ./faqcreator/forms.py
./faqcreator/models.py
./faqcreator/urls.py
./faqcreator/views.py
./tickets/admin.py
FaqCreator
App ./tickets/forms.py
./tickets/models.py
./tickets/urls.py
./tickets/views.py

66. Apps Depend on Other Apps

67. Apps Depend on Other Apps
faq creator

68. Apps Depend on Other Apps
faq creator
faq app

69. Apps Depend on Other Apps
faq creator
faq app
ticket

70. Apps Depend on Other Apps
faq creator
faq app
ticket
faq app

71. Apps Depend on Other Apps
faq creator
faq app version == 0.1
ticket
faq app version == 0.2

72. Apps Depend on Other Apps
pip install faq==0.1
pip install faq==0.2
pip freeze
faq==0.2

73. Apps Depend on Other Apps
faq creator
faq app version == 0.1
ticket
faq app version == 0.2

74. Back to APIs

75. What’s a service
Provider API_HOST= http://127.0.0.1

76. What’s a service
Provider API_HOST= http://127.0.0.1
Endpoint /v1/create/

77. What’s a service
Provider API_HOST= http://127.0.0.1
Endpoint /v1/create/
Contract {
‘question’: ‘foo bar’,
‘source’: 123
}

78. App

79. App
URLs Views Models

80. App
URLs Views Models
Service
Provider Endpoint Contract

81. A SERVICE means REUSABILITY
and enables SCALABILITY and
MAINTAINABILITY

82. Where to start

83. Where to start
1. If you’re monolithic, break up the apps first

84. Where to start
1. If you’re monolithic, break up the apps first
2. Port something that doesn’t require user

85. Where to start
1. If you’re monolithic, break up the apps first
2. Port something that doesn’t require user
3. Port where you have many dependencies

86. Porting an App
models.py
class Faq(models.Model):
title = models.CharField(max_length=100)
source = models.IntegerField(blank=True, null=True)
description = models.TextField()
solution = models.TextField()
def __unicode__(self):
return self.title

87. Porting an App
faqcreator/views.py
from faq.models import faq
i = Faq(title=‘foo’, description=‘bar’, solution=’la posta’)
i.save()

88. Turn it into an API

89. Turn it into an API
1. pip install django-tastypie

90. Turn it into an API
1. pip install django-tastypie
2. add tastypie to INSTALLED_APPS

91. Turn it into an API
1. pip install django-tastypie
2. add tastypie to INSTALLED_APPS
3. define your APIs

92. Create your API
from
faq/api.py
tastypie.resources import ModelResource
from faq.models import Faq
from django.contrib.auth.models import User
from tastypie.authentication import BasicAuthentication, DjangoAuthorization
from tastypie.authorization import Authorization
class FaqResource(ModelResource):
class Meta:
queryset = Faq.objects.all()
resource_name = 'faq'
list_allowed_methods = ['get', 'post']
authentication = BasicAuthentication()
authorization = Authorization()
def obj_create(self, bundle, request=None, **kwargs):
return super(FaqResource, self).obj_create(bundle, request, user=request.user)
def apply_authorization_limits(self, request, object_list):
return object_list.filter(user=request.user)

93. Create your API
api.py
class FaqResource(ModelResource):
class Meta:
queryset = Faq.objects.all()
resource_name = 'faq'
list_allowed_methods = ['get', 'post']
authentication = BasicAuthentication()
authorization = Authorization()
def obj_create(self, bundle, request=None, **kwargs):
return super(FaqResource, self).obj_create(
bundle, request, user=request.user)
def apply_authorization_limits(self, request, object_list):
return object_list.filter(user=request.user)

94. Create your API
api.py
class FaqResource(ModelResource):
class Meta:
queryset = Faq.objects.all()
resource_name = 'faq'
list_allowed_methods = ['get', 'post']
authentication = BasicAuthentication()
authorization = Authorization()
def obj_create(self, bundle, request=None, **kwargs):
return super(FaqResource, self).obj_create(
bundle, request, user=request.user)
def apply_authorization_limits(self, request, object_list):
return object_list.filter(user=request.user)

95. Create your API
api.py
class FaqResource(ModelResource):
class Meta:
queryset = Faq.objects.all()
resource_name = 'faq'
list_allowed_methods = ['get', 'post']
authentication = BasicAuthentication()
authorization = Authorization()
def obj_create(self, bundle, request=None, **kwargs):
return super(FaqResource, self).obj_create(
bundle, request, user=request.user)
def apply_authorization_limits(self, request, object_list):
return object_list.filter(user=request.user)

96. Create your API
api.py
class FaqResource(ModelResource):
class Meta:
queryset = Faq.objects.all()
resource_name = 'faq'
list_allowed_methods = ['get', 'post']
authentication = BasicAuthentication()
authorization = Authorization()
def obj_create(self, bundle, request=None, **kwargs):
return super(FaqResource, self).obj_create(
bundle, request, user=request.user)
def apply_authorization_limits(self, request, object_list):
return object_list.filter(user=request.user)

97. Create your API
api.py
class FaqResource(ModelResource):
class Meta:
queryset = Faq.objects.all()
resource_name = 'faq'
list_allowed_methods = ['get', 'post']
authentication = BasicAuthentication()
authorization = Authorization()
def obj_create(self, bundle, request=None, **kwargs):
return super(FaqResource, self).obj_create(
bundle, request, user=request.user)
def apply_authorization_limits(self, request, object_list):
return object_list.filter(user=request.user)

98. Create your API
api.py
class FaqResource(ModelResource):
class Meta:
queryset = Faq.objects.all()
resource_name = 'faq'
list_allowed_methods = ['get', 'post']
authentication = BasicAuthentication()
authorization = Authorization()
def obj_create(self, bundle, request=None, **kwargs):
return super(FaqResource, self).obj_create(
bundle, request, user=request.user)
def apply_authorization_limits(self, request, object_list):
return object_list.filter(user=request.user)

99. Create your API
urls.py
from faq.api import FaqResource
from tastypie.api import Api
v1_api = Api(api_name='v1')
v1_api.register(FaqResource())
urlpatterns = patterns('',
url(r'^api/', include(v1_api.urls)),
)

100. Use your API
curl -H "Content-Type: application/json"
--user admin:testing
-X POST
--data
'{"title": "New FAQ",
"source": "1",
"description": "foo",
"solution": "bar"}'
http://127.0.0.1:8000/api/v1/faq/

101. Use it in Python

102. Use it in Python
data = {
'title': 'New FAQ',
'source': '1',
'description': 'foo',
'solution': 'bar'
}
r = requests.post(os.environ[‘FAQ_API’] + "api/v1/faq/",
data=data,
auth=('admin', 'testing'))

103. Version Bump

104. Version Bump
data = {
'title': 'New FAQ',
'source': '1',
'description': 'foo',
'solution': 'bar',
'related': ['123', '456']
}
r = requests.post(os.environ[‘FAQ_API’] + "api/v2/faq/",
data=data,
auth=('admin', 'testing'))

105. Version Bump

106. Version Bump
data = {
'title': 'New FAQ',
'source': '1',
'description': 'foo',
'solution': 'bar',
'related': ['123', '456']
}
r = requests.post(os.environ[‘FAQ_API’] + "api/v2/faq/",
data=data,
auth=('admin', 'testing'))

107. In our Application
faq_creator/views.py
ticket/views.py

108. In our Application
faq_creator/views.py
r = requests.post(os.environ[‘FAQ_API’] + "api/v2/faq/",
data=data,
auth=('admin', 'testing'))
ticket/views.py
r = requests.post(os.environ[‘FAQ_API’] + "api/v1/faq/",
data=data,
auth=('admin', 'testing'))

109. cd myproject && find .
Reusability
cd myproject && find .
manage.py
requirements.txt manage.py
settings.py requirements.txt
urls.py settings.py
./faq/admin.py urls.py
-->
./faq/forms.py
./faq/models.py cat myproject/requirements.txt
./faq/urls.py
./faq/views.py faq==0.1
./faqcreator/admin.py faqcreator==0.1
./faqcreator/forms.py tickets==0.1
./faqcreator/models.py
./faqcreator/urls.py
./faqcreator/views.py
./tickets/admin.py
./tickets/forms.py
./tickets/models.py
./tickets/urls.py
./tickets/views.py

110. Maintainability/Scalability/Agility
cd myproject && find . ls projects
manage.py faq-service
requirements.txt myproject
settings.py cd faq-service && find .
urls.py manage.py
requirements.txt
cat myproject/requirements.txt
faq==0.1
--> settings.py
urls.py
cd myproject && find .
faqcreator==0.1
tickets==0.1 manage.py
requirements.txt
settings.py
urls.py
cat myproject/requirements.txt
faqcreator==0.1
tickets==0.1

111. Maintainability/Scalability/Agility

112. Maintainability/Scalability/Agility
Faq Project
- Its own Django project
- 1 Django app
- Own database
- Own deployment

113. Maintainability/Scalability/Agility
My Project Faq Project
- Contained Django Project - Its own Django project
- 2 Django apps - 1 Django app
- Own database - Own database
- Own deployment - Own deployment

114. Take aways

115. Take aways
1. Start non-critical (Cheat)
2. Create services where theres app reuse
3. Create services where theres pain
4. Start small

116. Others

117. Others
1. Expect APIs to fail
2. Flask is great for APIs
3. Make it easy to setup/test

118. Fin.
Resources
http://www.craigkerstiens.com
http://bit.ly/djangoappstoservices/
http://www.12factor.net
http://github.com/craigkerstiens/