Python Django在PostgreSQL死亡时未重新连接，是否需要自定义后端？

我已经做了一些测试，并且能够确认使用

Django

与

PostgreSQL

和

PGBouncer

时，它不会在失去连接时自动重新连接。老实说，我不确定这是一个bug还是设计的。如果它是一个错误，我会很高兴地报告它，如果不是，我想一些解释为什么和如何绕过它，而不是另一个自定义后端

通过在

Django 1.8.4

和

Django 1.8.6

上执行以下操作，我相当轻松地完成了这些测试：

>>>Model.objects.all().count()
24
# Restart postgres with `sudo service postgres restart`
>>>Model.objects.all().count()
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 318, in count
    return self.query.get_count(using=self.db)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 466, in get_count
    number = obj.get_aggregation(using, ['__count'])['__count']
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 447, in get_aggregation
    result = compiler.execute_sql(SINGLE)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/compiler.py", line 840, in execute_sql
    cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 98, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
OperationalError: server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.

现在来看看代码：

from django.db.backends.postgresql_psycopg2.base import DatabaseError, \
    IntegrityError, DatabaseWrapper as PostgresWrapper

class DatabaseWrapper(PostgresWrapper):
    def _reconnect(self):
        try:
            self.connect()
        except (DatabaseError, OperationalError):
            pass

    def ensure_connection(self):
        """
        Guarantees that a connection to the database is established.
        """
        if self.connection is None:
            with self.wrap_database_errors:
                self._reconnect()
        else:
            try:
                self.connection.cursor().execute('SELECT 1')
            except (DatabaseError, OperationalError):
                self._reconnect()

---

我想我终于明白了。我不完全确定我的第一种方法有什么问题，但这一种似乎工作得更好

class DatabaseWrapper(PostgresWrapper):
    def _cursor(self):
        if self.connection is not None:
            if not self.is_usable():
                self.connection.close()
                self.connection = None
        return super(DatabaseWrapper, self)._cursor()

编辑：最终公开了这项工作。我不确定它是否100%需要，但在服务器上重新启动Postgres服务后，它工作正常。您可以在pypi上找到它，它的名称是django postgreconnect，也可以在GitHub上找到它

class DatabaseWrapper(PostgresWrapper):
    def _cursor(self):
        if self.connection is not None:
            if not self.is_usable():
                self.connection.close()
                self.connection = None
        return super(DatabaseWrapper, self)._cursor()