在多處理中使用mongoengine-如何關閉mongoengine連接？

Question

不管我嘗試什么，當嘗試在mongoengine db上使用多處理時，我都會不斷遇到“在fork之前打開MongoClient的警告”，該警告關於未分叉活動的mongo連接。 標准的mongo建議似乎僅是從子進程內部連接到db，但我認為我的工作在功能上應等效，因為我在使用多處理之前關閉了數據庫，但是仍然遇到了問題。

相關的問題或者沒有一個最小的例子或不適用的解決方案是在這里 ， 這里 ，具體而言為燒瓶/芹菜和的情況下， 這里

重現該問題的最小示例：

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會在各處緩存與數據庫的連接。 如果您手動刪除它們，則此問題已解決。 添加以下導入

from mongoengine import connection

然后添加：

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

Base._collection = None
Parent._collection = None

進入“ #close db”部分以解決該問題。

完整的代碼：

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

最近得到了改進，從MongoEngine> = 0.18.0開始，應該使用方法connector disconnect()和disconnect_all()分別斷開1個或所有現有的連接（ changelog 0.18.0 ）

見官方文件