Introduction to Google App Engine

Introduction to
Google App Engine
Luke Francl

Server Virtual Server Process Request

App Engine
Restrictions

• No access to servers • No C extensions

• Read-only ﬁle system • No sockets

• 30 second response limit • Python, Java, Go

• Non-relational datastore

photo:
Kash_if

EC2 versus App
EngineApp Engine
EC2
Instance $0.02 - $0.68 (15
$0.08
Hour GB RAM, 8x1GHz
CPU) $0.08 - $0.64 (1G RAM,
Background same as above
4.8GHz CPU)
Autoscaling with effort automatic

Storage SimpleDB, RDS, Datastore, Blobstore, Google
EBS, S3 Storage (S3 clone)
Python, Java, Go (written for
Runs Anything!
GAE's API)
APIs S3, SQS, SES, Storage, BigQuery, Prediction
many more API

Heroku vs App
EngineApp Engine
Heroku
Free 750 instance
28 instance hours/day
Processing hours/mo
$0.05/hour tasks (run on web instances)
Background
(no autoscaling) Backends: $0.08 - $0.68/
5 MB free, ≈$70/ hour
Memcache lots!
GB
Ruby, Clojure,
Runs Java, Python, Go
Java, Node.js,
Python N/A
SSL $5-$100/mo
(site.appspot.com only)
Deploy git push appcfg.py upload

Totally awesome
things about App
Engine

http://<version>.<app‐id>.appspot.com

Getting Started

or dev_appserver.py

http://code.google.com/appengine/downloads.html

from google.appengine.ext import webapp

class UserHandler(webapp.RequestHandler):

  def get(self):
    key_name = self.request.get('user_id')
    user = User.get_by_key_name(key_name)

    html = "<html><body><p>hello, %s</p></body></html>"
    self.response.out.write(html % user.email)

app = webapp.WSGIApplication([('/user', 
                               UserHandler)])

if __name__ == '__main__':
      util.run_wsgi_app(app)

The Datastore

photo:

class User(db.Model):
    email    = db.EmailProperty(required=True)
    password = db.StringProperty(required=True)
    age      = db.IntegerProperty()
    website  = db.LinkProperty()
    notes    = db.TextProperty()

user = User(key_name='foobar', 
            email='look@example.com',
            password=encrypt('foobar', salt),
            website='http://example.com')
user.put()

key = db.Key.from_path('User', 'foobar',
                       'Preferences', 123)

prefs = Preferences.get(key)

user = User.get_by_key_name('foobar')

prefs = Preferences.get_by_id(123,
                              parent=user)

def txn(user, items_per_page, bg_color):
  user.put()
  prefs = Preferences(parent=user,
                      items_per_page=items_per_page,
                      bg_color=bg_color)
  prefs.put()

user = User(key_name='example',
            email='user@example.com')

db.run_in_transaction(txn, user, 100, 'ff0000')

Querying
query = User.all()
query.filter("age >=", 42)
query.order("age")

# get list of up to 100 users
users = query.fetch(100)

# iterate over all users (until you run out of time)
for user in query:
  # do stuff with user

Custom Index
Query
# requires custom index
query.filter("website =", "http://example.com")

# index.yaml
indexes:

‐ kind: User
  properties:
  ‐ name: age
  ‐ name: email
    direction: asc

Invalid Queries

query.filter("email >=", "abc")

query.order("email")

following = Follow.all().
filter("user =", current_user)

Post.all().filter("user in", 
following).order("‐created_at")

User

TimelinePos
Post Follow
t

TimelinePost.all().
filter("delivered_to", current_user).
order("‐created_at")

Follow along at:
http://bitbucket.org/look/sputter

...but it is moving
fast
≈ 1 release/month

• Backends • Bulk import/export

• Always on instances • High replication datastore

• Blobstore • MapReduce API

• Image serving & thumbnailing • Browser-push "Channel" API

• Remove fetch/count limits • Namespaces/Multitenancy

photo: Stig
Nygaard

On the road map

• SSL for your own domain
• Full-text search
• Python 2.7
• Hosted SQL

Introduction to Google App Engine

Introduction to Google App Engine

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (20)

Destacado

Destacado (7)

Similar a Introduction to Google App Engine

Similar a Introduction to Google App Engine (20)

Último

Último (20)

Introduction to Google App Engine

Notas del editor