django-orchestra-test/orchestra/apps/orchestration/middlewares.py

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import copy
from threading import local
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from django.core.urlresolvers import resolve
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from django.db.models.signals import pre_delete, post_save
from django.dispatch import receiver
from django.http.response import HttpResponseServerError
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from orchestra.utils.python import OrderedSet
from .backends import ServiceBackend
from .helpers import message_user
from .models import BackendLog
from .models import BackendOperation as Operation
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@receiver(post_save, dispatch_uid='orchestration.post_save_collector')
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def post_save_collector(sender, *args, **kwargs):
if sender != BackendLog:
OperationsMiddleware.collect(Operation.SAVE, **kwargs)
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@receiver(pre_delete, dispatch_uid='orchestration.pre_delete_collector')
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def pre_delete_collector(sender, *args, **kwargs):
if sender != BackendLog:
OperationsMiddleware.collect(Operation.DELETE, **kwargs)
class OperationsMiddleware(object):
"""
Stores all the operations derived from save and delete signals and executes them
at the end of the request/response cycle
"""
# Thread local is used because request object is not available on model signals
thread_locals = local()
@classmethod
def get_pending_operations(cls):
# Check if an error poped up before OperationsMiddleware.process_request()
if hasattr(cls.thread_locals, 'request'):
request = cls.thread_locals.request
if not hasattr(request, 'pending_operations'):
request.pending_operations = OrderedSet()
return request.pending_operations
return set()
@classmethod
def collect(cls, action, **kwargs):
""" Collects all pending operations derived from model signals """
request = getattr(cls.thread_locals, 'request', None)
if request is None:
return
pending_operations = cls.get_pending_operations()
for backend in ServiceBackend.get_backends():
instance = None
if backend.is_main(kwargs['instance']):
instance = kwargs['instance']
else:
candidate = backend.get_related(kwargs['instance'])
if candidate:
delete = Operation.create(backend, candidate, Operation.DELETE)
if delete not in pending_operations:
instance = candidate
# related objects with backend.model trigger save()
action = Operation.SAVE
if instance is not None:
# Prevent creating a deleted instance by deleting existing saves
if action == Operation.DELETE:
save = Operation.create(backend, instance, Operation.SAVE)
try:
pending_operations.remove(save)
except KeyError:
pass
else:
update_fields = kwargs.get('update_fields', None)
if update_fields:
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# "update_fileds=[]" is a convention for explicitly executing backend
# i.e. account.disable()
if not update_fields == []:
execute = False
for field in update_fields:
if field not in backend.ignore_fields:
execute = True
break
if not execute:
continue
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instance = copy.copy(instance)
pending_operations.add(Operation.create(backend, instance, action))
def process_request(self, request):
""" Store request on a thread local variable """
type(self).thread_locals.request = request
def process_response(self, request, response):
""" Processes pending backend operations """
if not isinstance(response, HttpResponseServerError):
operations = type(self).get_pending_operations()
if operations:
logs = Operation.execute(operations)
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if logs and resolve(request.path).app_name == 'admin':
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message_user(request, logs)
return response