Question

我有一个返回TimeOut的Sql Alchemy应用程序：

TimeoutError：达到大小为5的QueuePool限制10，连接超时，超时30

我在另一篇文章中读到，当我不关闭会话时会发生这种情况，但我不知道这是否适用于我的代码：

我在init.py中连接数据库：

from .dbmodels import (
    DBSession,
    Base,    

engine = create_engine("mysql://" + loadConfigVar("user") + ":" + loadConfigVar("password") + "@" + loadConfigVar("host") + "/" + loadConfigVar("schema"))

#Sets the engine to the session and the Base model class
DBSession.configure(bind=engine)
Base.metadata.bind = engine

然后在另一个python文件中，我在两个函数中收集了一些数据但是使用了我在init.py中初始化的DBSession：

from .dbmodels import DBSession
from .dbmodels import resourcestatsModel

def getFeaturedGroups(max = 1):

    try:
        #Get the number of download per resource
        transaction.commit()
        rescount = DBSession.connection().execute("select resource_id,count(resource_id) as total FROM resourcestats")

        #Move the data to an array
        resources = []
        data = {}
        for row in rescount:
            data["resource_id"] = row.resource_id
            data["total"] = row.total
            resources.append(data)

        #Get the list of groups
        group_list = toolkit.get_action('group_list')({}, {})
        for group in group_list:
            #Get the details of each group
            group_info = toolkit.get_action('group_show')({}, {'id': group})
            #Count the features of the group
            addFesturedCount(resources,group,group_info)

        #Order the FeaturedGroups by total
        FeaturedGroups.sort(key=lambda x: x["total"],reverse=True)

        print FeaturedGroups
        #Move the data of the group to the result array.
        result = []
        count = 0
        for group in FeaturedGroups:
            group_info = toolkit.get_action('group_show')({}, {'id': group["group_id"]})
            result.append(group_info)
            count = count +1
            if count == max:
                break

        return result
    except:
        return []


    def getResourceStats(resourceID):
        transaction.commit()
        return  DBSession.query(resourcestatsModel).filter_by(resource_id = resourceID).count()

会话变量的创建如下：

#Basic SQLAlchemy types
from sqlalchemy import (
    Column,
    Text,
    DateTime,
    Integer,
    ForeignKey
    )
# Use SQLAlchemy declarative type
from sqlalchemy.ext.declarative import declarative_base

#
from sqlalchemy.orm import (
    scoped_session,
    sessionmaker,
    )

#Use Zope' sqlalchemy  transaction manager
from zope.sqlalchemy import ZopeTransactionExtension

#Main plugin session
DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))

因为会话是在init.py和后续代码中创建的，所以我只是使用它;那时我需要关闭会话？或者我还需要做些什么来管理池大小？

Answer 1

您可以通过在函数create_engine中添加参数pool_size和max_overflow来管理池大小

engine = create_engine("mysql://" + loadConfigVar("user") + ":" + loadConfigVar("password") + "@" + loadConfigVar("host") + "/" + loadConfigVar("schema"), 
                        pool_size=20, max_overflow=0)

参考是here

您不需要关闭会话，但应在交易完成后关闭连接。替换：

rescount = DBSession.connection().execute("select resource_id,count(resource_id) as total FROM resourcestats")

人：

connection = DBSession.connection()
try:
    rescount = connection.execute("select resource_id,count(resource_id) as total FROM resourcestats")
    #do something
finally:
    connection.close()

参考是here

另外，请注意已经过时的mysql连接在特定时间段后关闭（这段时间可以在MySQL中配置，我不记得默认值），所以你需要通过pool_recycle值为您的引擎创建

Answer 2

在代码中添加以下方法。它将自动关闭所有未使用/挂起的连接并防止代码中出现瓶颈。尤其是如果您使用以下语法Model.query.filter_by（attribute = var）.first（）和关系/延迟加载。

   @app.teardown_appcontext
    def shutdown_session(exception=None):
        db.session.remove()

有关此文档，请参见：http://flask.pocoo.org/docs/1.0/appcontext/

Answer 3

此外，您可以在def末尾使用engine.dispose()方法。这样可以完全关闭所有当前已检查的数据库连接。

Sql Alchemy QueuePool限制溢出

3 个答案: