在多处理中使用mongoengine-如何关闭mongoengine连接？

Question

不管我尝试什么，当尝试在mongoengine db上使用多处理时，我都会不断遇到“在fork之前打开MongoClient的警告”，该警告关于未分叉活动的mongo连接。 标准的mongo建议似乎仅是从子进程内部连接到db，但我认为我的工作在功能上应等效，因为我在使用多处理之前关闭了数据库，但是仍然遇到了问题。

相关的问题或者没有一个最小的例子或不适用的解决方案是在这里 ， 这里 ，具体而言为烧瓶/芹菜和的情况下， 这里

重现该问题的最小示例：

from mongoengine import connect, Document, StringField, ListField, ReferenceField
from pathos.multiprocessing import ProcessingPool


class Base(Document):
    key = StringField(primary_key=True)
    name = StringField()
    parent = ReferenceField('Parent', required=True)

class Parent(Document):
    key = StringField(primary_key=True)
    name = StringField()
    bases = ListField(ReferenceField('Base'))


def remove_base(key):
   db = connect('mydb')
   mongo_b = Base.objects().get(key=key)
   mongo_b.parent.update(pull__bases=mongo_b)
   mongo_b.delete()


### setup
db = connect('mydb', connect=False)

Base(key='b1', name='test', parent='p1').save()
Base(key='b2', name='test', parent='p1').save()
Base(key='b3', name='test2', parent='p1').save()

p=Parent(key='p1', name='parent').save()
p.update(add_to_set__bases='b1')
p.update(add_to_set__bases='b2')
p.update(add_to_set__bases='b3')

### find objects we want to delete
my_base_objects = Base.objects(name='test')
keys = [b.key for b in my_base_objects]
del my_base_objects

# close db to avoid problems?!
db.close()
del db

# parallel map removing base objects and references from the db
# warning generated here
pp = ProcessingPool(2)
pp.map(remove_base, keys)

Answer 1

好的，所以我知道了。 Mongoengine会在各处缓存与数据库的连接。 如果您手动删除它们，则此问题已解决。 添加以下导入

from mongoengine import connection

然后添加：

connection._connections = {}
connection._connection_settings ={}
connection._dbs = {}

Base._collection = None
Parent._collection = None

进入“ #close db”部分以解决该问题。

完整的代码：

from mongoengine import connect, Document, StringField, ListField, ReferenceField, connection
from pathos.multiprocessing import ProcessingPool


class Base(Document):
    key = StringField(primary_key=True)
    name = StringField()
    parent = ReferenceField('Parent', required=True)

class Parent(Document):
    key = StringField(primary_key=True)
    name = StringField()
    bases = ListField(ReferenceField('Base'))


def remove_base(key):
   db = connect('mydb', connect=False)
   mongo_b = Base.objects().get(key=key)
   mongo_b.parent.update(pull__bases=mongo_b)
   mongo_b.delete()

def setup():
    Base(key='b1', name='test', parent='p1').save()
    Base(key='b2', name='test', parent='p1').save()
    Base(key='b3', name='test2', parent='p1').save()

    p=Parent(key='p1', name='parent').save()
    p.update(add_to_set__bases='b1')
    p.update(add_to_set__bases='b2')
    p.update(add_to_set__bases='b3')

db = connect('mydb', connect=False)
setup()
### find objects we want to delete
my_base_objects = Base.objects(name='test')
keys = [b.key for b in my_base_objects]
del my_base_objects


### close db to avoid problems?!
db.close()
db = None

connection._connections = {}
connection._connection_settings ={}
connection._dbs = {}

Base._collection = None
Parent._collection = None

### parallel map removing base objects from the db
pp = ProcessingPool(2)
pp.map(remove_base, keys)

Answer 2

最近得到了改进，从MongoEngine> = 0.18.0开始，应该使用方法connector disconnect()和disconnect_all()分别断开1个或所有现有的连接（ changelog 0.18.0 ）

见官方文件