mysql 断开连接解决方法 (2013, 'Lost connection to MySQL server during query') （mysql have gone away）

1，出现该问题的原因，代码里导入了mysql的一个连接，但是长时间没有操作，超过了mysql的awiat_timeout 时间（默认8小时）

2，解决思路：

　　1，修改mysql 的await_timeout （不建议）

　　2，django 中使用 close_old_connections()  关闭旧的连接  （from django.db import close_old_connections）  

　　　　（该方法一般在django 的脚本中使用）

from django.db import close_old_connections

def index():
    close_old_connections()
    s = Student.objects.all()

　　3，django 的视图函数中使用可以定义中间件 （请求开始时连接，请求结束后断开） （使用的可能性不大）

# middleware.py
from my_blog.db import database  
# Import the peewee database instance.


def PeeweeConnectionMiddleware(get_response):
    def middleware(request):
        database.connect()
        try:
            response = get_response(request)
        finally:
            if not database.is_closed():
                database.close()
        return response
    return middleware

　　4，flask 中解决思路：和django中一样，在请求来时连接，在请求结束后断开

# app.py
from bottle import hook  #, route, etc, etc.
from peewee import *

db = SqliteDatabase('my-bottle-app.db')

@hook('before_request')
def _connect_db():
    db.connect()

@hook('after_request')
def _close_db():
    if not db.is_closed():
        db.close()

# Rest of your bottle app goes here.

 　　5，如果是使用peewee ，在模型类连接时修改继承类，后面正常使用就ok  (可能性比较大)

from peewee import *
from peewee import __exception_wrapper__

class RetryOperationalError(object):
    def execute_sql(self, sql, params=None, commit=True):
        try:
            cursor = super(RetryOperationalError, self).execute_sql(sql, params, commit)
        except OperationalError:
            if not self.is_closed():
                self.close()
            with __exception_wrapper__:
                cursor = self.cursor()
                cursor.execute(sql, params or ())
                if commit and not self.in_transaction():
                    self.commit()
        return cursor


class RetryMySQLDatabase(RetryOperationalError, MySQLDatabase):
    pass


database = RetryMySQLDatabase('sql_test', **{'charset': 'utf8', 'sql_mode': 'PIPES_AS_CONCAT', 'use_unicode': True, 'host': '127.0.0.1', 'port': 3306, 'user': 'root', 'password': 'mysql'})

class UnknownField(object):
    def __init__(self, *_, **__): pass

class BaseModel(Model):
    class Meta:
        database = database

class Teacher(BaseModel):
    depart = CharField()
    prof = CharField(null=True)
    tbirthday = DateTimeField(null=True)
    tname = CharField()
    tno = CharField(primary_key=True)
    tsex = CharField()

    class Meta:
        table_name = 'teacher'

class Course(BaseModel):
    cname = CharField()
    cno = CharField()
    tno = ForeignKeyField(column_name='tno', field='tno', model=Teacher)

    class Meta:
        table_name = 'course'

class DjangoMigrations(BaseModel):
    app = CharField()
    applied = DateTimeField()
    name = CharField()

    class Meta:
        table_name = 'django_migrations'

class Emp(BaseModel):
    deptno = CharField(null=True)
    duty = CharField(null=True)
    empid = AutoField()
    name = CharField(null=True)
    sal = CharField(null=True)

    class Meta:
        table_name = 'emp'

　　6，tornado 解决方法如下

from tornado.web import RequestHandler

db = SqliteDatabase('my_db.db')

class PeeweeRequestHandler(RequestHandler):
    def prepare(self):
        db.connect()
        return super(PeeweeRequestHandler, self).prepare()

    def on_finish(self):
        if not db.is_closed():
            db.close()
        return super(PeeweeRequestHandler, self).on_finish()