1. Python alapú mobil
backend GAE felett
by Gyuri Horak

2. GAE Python
● Python 2.7
● WSGI, webapp2
● db, memcache, cloud-sql, url fetch,
blobstore, users, unit testing ...
● django (django-nonrel, django+cloud-sql)

3. Példaprojekt
● backend iOS, Android és weboldal számára
● REST/JSON

4. Flask
Flask microframework, @mitsuhiko
● url routing
● class based views
● debugger, gae-profiler
● ...

5. JSONView
● Flask.views.MethodView
● success és failure metódusok
● X-Location header
● néhány Exception kezelése

6. ExceptionHandlerViewMeta
class ReferenceErrorMeta(MethodViewType):
def __new__(mcs, name, bases, odict):
if 'get' in odict:
odict['get'] = mcs.wrapmethod(odict['get'])
return MethodViewType.__new__(mcs, name, bases, odict)
@staticmethod
def wrapmethod(method):
@wraps(method)
def wrapper(self, *args, **kwargs):
try:
return method(self, *args, **kwargs)
except db.ReferencePropertyResolveError:
return self.failure(10, 'Reference object seems to be deleted.')
return wrapper

7. DB: a lekérdezés pénz
● NE előre optimalizálj!
● cache: memcache, request scope cache
● aggregálni, okosan
● Mérj! (GAE profiler, datastore stats)

8. CachedModel
class CachedModel(db.Model):
@classmethod
def get_from_cache(id):
...
@classmethod
def get(cls, key):
obj = cls.get_from_cache(key.id())
if not obj:
obj = super(CachedModel, cls).get(key)
return obj
def put(self):
super(CachedModel, self).put()
self.update_in_cache()
def delete(self):
super(CachedModel, self).delete()
self.remove_in_cache()
def __eq__(self, other):
return self.key() == other.key()

9. class CachedReferenceProperty(db.ReferenceProperty):
def __get__(self, model_instance, model_class):
...
# instance = get(reference_id) # WTF?
instance = self.reference_class.get(reference_id)
if instance is None:
# Feature check vs. isinstance
if hasattr(model_instance, 'update_references'):
model_instance.update_references()
raise db.ReferencePropertyResolveError(...)
CachedReferenceProperty

10. class CachedReferenceProperty(db.ReferenceProperty):
def __get__(self, model_instance, model_class):
...
# instance = get(reference_id) # WTF?
instance = self.reference_class.get(reference_id)
if instance is None:
# Feature check vs. isinstance
if hasattr(model_instance, 'update_references'):
model_instance.update_references()
raise db.ReferencePropertyResolveError(...)
Aggregáció

11. Aggregáció
Sérülhet, akár rajtunk kívül álló okok miatt
is.
● cron jobok takarítani / update-elni
● javítás, amikor hibát találunk

12. Képkezelés
● blobstore
○ create_upload_url()
○ files API (experimental)
● images ~ PIL
● get_serving_url()
○ lehet, hogy nincs kész

13. Geomodel
● db.GeoPt(lat, lon)
● geocells
● bounding box és proximity lekérdezés
localmind is ezt használja clustering
megoldásként