Mongoengine 连接失败：您尚未定义默认连接答案

【问题标题】：Mongoengine Connection Failure: You have not defined a default connectionMongoengine 连接失败：您尚未定义默认连接
【发布时间】：2021-10-26 18:26:58
【问题描述】：

启动一个 python 项目，使用 fastapi 和 mongoengine。昨天运行正常，但是今天运行任何连接数据库的方法时，出现连接失败错误（mongoengine.connection.ConnectionFailure: You have not defined a default connection）。

我的连接：

from mongoengine import connect

connect(db="mydb", host='localhost', port=27017, alias='default')

我的模型：

from mongoengine.document import Document
from mongoengine.fields import StringField, BooleanField, ListField, ReferenceField
from mongoengine import PULL


class Permissao(Document):
    permissao = StringField()


class Grupo(Document):
    grupo = StringField()
    
    permissoes = ListField(ReferenceField('Permissao', reverse_delete_rule=PULL))


class Usuario(Document):
    nome_usuario = StringField()
    ativo = BooleanField()
    senha = StringField()
    
    grupos = ListField(ReferenceField('Grupo', reverse_delete_rule=PULL))
    permissoes = ListField(ReferenceField('Permissao', reverse_delete_rule=PULL))

【问题讨论】：

标签： python fastapi mongoengine

【解决方案1】：

成功了，我切换到模型的连接并放置了一个元字段，在下面检查：

from mongoengine.document import Document
from mongoengine.fields import StringField, BooleanField, ListField, ReferenceField
from mongoengine import PULL
from mongoengine import connect

connect(db="mydb", host="localhost", port=27017, alias="mydb-alias")

class Permissao(Document):
    permissao = StringField()

    meta = {"db_alias" : "mydb-alias" , "collection" : "permissao"}


class Grupo(Document):
    grupo = StringField()
    
    permissoes = ListField(ReferenceField('Permissao', reverse_delete_rule=PULL))
    
    meta = {"db_alias" : "mydb-alias" , "collection" : "grupo"}


class Usuario(Document):
    nome_usuario = StringField()
    ativo = BooleanField()
    senha = StringField()
    
    grupos = ListField(ReferenceField('Grupo', reverse_delete_rule=PULL))
    permissoes = ListField(ReferenceField('Permissao', reverse_delete_rule=PULL))

    meta = {"db_alias" : "mydb-alias" , "collection" : "usuario"}

【讨论】：