postgresql – 如何使Flask SQLAlchemy重用数据库连接？

Flask==0.8
Flask-SQLAlchemy==0.16
psycopg2==2.4.5

当我的测试套件运行打开的连接数爬到20(在postgresql.conf中的max_connections设置)，然后我看到：

OperationalError: (OperationalError) FATAL:  sorry,too many clients already
 None None

我已经将代码缩小到只需调用create_all和drop_all(但不会发出任何sql，因为没有模型)。

我看到在日志中检入和取出的连接：

DEBUG:sqlalchemy.pool.QueuePool:Connection <connection object at 0x101c1dff0; dsn: 'dbname=cx_test host=localhost',closed: 0> checked out from pool
DEBUG:sqlalchemy.pool.QueuePool:Connection <connection object at 0x101c1dff0; dsn: 'dbname=cx_test host=localhost',closed: 0> being returned to pool
WARNING:root:impl   <-------- That's the test running
DEBUG:sqlalchemy.pool.QueuePool:Connection <connection object at 0x101c1dff0; dsn: 'dbname=cx_test host=localhost',closed: 0> being returned to pool

对于每个测试运行，连接的地址(“xyz的连接对象”部分)是不同的。我怀疑这与问题有关，但我不知道如何进一步调查。

下面的代码在新的venv中再现了问题：

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
from unittest import TestCase

import logging
logging.basicConfig(level=logging.DEBUG)
logging.getLogger('sqlalchemy.pool').setLevel(logging.DEBUG)
logging.getLogger('sqlalchemy.engine').setLevel(logging.DEBUG)
logging.getLogger('sqlalchemy.dialects').setLevel(logging.DEBUG)
logging.getLogger('sqlalchemy.orm').setLevel(logging.DEBUG)


db = SQLAlchemy()

def create_app(config=None):
    app = Flask(__name__)
    app.config.from_object(config)
    db.init_app(app)
    return app


class AppTestCase(TestCase):
    SQLALCHEMY_DATABASE_URI = "postgresql://localhost/cx_test"
    TESTING = True

    def create_app(self):
        return create_app(self)

    def setUp(self):
        self.app = self.create_app()
        self.client = self.app.test_client()
        self._ctx = self.app.test_request_context()
        self._ctx.push()
        db.create_all()

    def tearDown(self):
        db.session.remove()
        db.drop_all()
        self._ctx.pop()


class TestModel(AppTestCase):
    def impl(self):
        logging.warn("impl")
        pass

    def test_01(self):
        self.impl()

    def test_02(self):
        self.impl()

    def test_03(self):
        self.impl()

    def test_04(self):
        self.impl()

    def test_05(self):
        self.impl()

    def test_06(self):
        self.impl()

    def test_07(self):
        self.impl()

    def test_08(self):
        self.impl()

    def test_09(self):
        self.impl()

    def test_10(self):
        self.impl()

    def test_11(self):
        self.impl()

    def test_12(self):
        self.impl()

    def test_13(self):
        self.impl()

    def test_14(self):
        self.impl()

    def test_15(self):
        self.impl()

    def test_16(self):
        self.impl()

    def test_17(self):
        self.impl()

    def test_18(self):
        self.impl()

    def test_19(self):
        self.impl()



if __name__ == "__main__":
    import unittest
    unittest.main()

这是我第一次在烧瓶中使用应用程序工厂，我从Flask-SQLAlchemy docs.部分复制了这个代码。Elseware这些文档提到在错误的上下文中使用数据库会导致连接泄漏 – 也许我正在做不正确的init？