Dockerizing Flask Web App 后定期“在查询期间丢失与 MySQL 服务器的连接”

Question

我有一个 Flask Web 应用程序，它曾经使用以下内容在独立服务器上运行：

• 烧瓶/SQLAlchemy
• 玛丽亚数据库
• uwsgi
• nginx

在独立服务器上，此应用程序运行良好。

我已经在两个容器中“dockerized”了这个应用程序：

• uwsgi-nginx-flask
• 玛丽亚数据库

自从 dockerizing 以来，我偶尔会收到此错误（最后发布了整个回溯）：

Lost connection to MySQL server during query

MariaDB 日志在详细日志记录中显示以下错误：

2020-05-10 18:35:32 130 [Warning] Aborted connection 130 to db: 'flspection2' user: 'fl-server' host: '172.19.0.1' (Got an error reading communication packets)
2020-05-10 18:45:34 128 [Warning] Aborted connection 128 to db: 'flspection2' user: 'fl-server' host: '172.19.0.1' (Got timeout reading communication packets)

这是用户作为502 Bad Gateway. 如果用户刷新页面，这通常会解决问题。这个问题是随机出现的。我无法随意重现它，但随着时间的流逝，它不可避免地会出现。

这是什么原因造成的，我该如何解决？

我所做的：

• 验证 MariaDB 容器的超时时间为 28800。我已经看到在重新启动所有容器后该错误发生的时间比 28800 秒要早得多，所以我认为这实际上不是超时问题。
• 将pool_recycle选项设置为120
• 验证烧瓶SQLAlchemy中使用scoped_session它应该避免这些超时的问题。
• network_mode根据评论更改为默认值。这并没有解决问题。

我的想法是它就像flask和数据库之间的连接不可靠一样，但是作为运行在同一主机上的docker容器，这不是很可靠吗？

相关代码：

数据库.py

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

配置文件

class Config:
    ...
    SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://username:password@127.0.0.1/database?charset=utf8mb4'
    SQLALCHEMY_TRACK_MODIFICATIONS = False
    SQLALCHEMY_ENGINE_OPTIONS = {
        'pool_recycle': 120
    }
    ...

docker-compose.yml

version: "3.7"
services:
  db:
    restart: "always"
    build: ./docker/db
    volumes:
      - "~/db:/var/lib/mysql"
    environment:
      MYSQL_ROOT_PASSWORD: "password"
      MYSQL_DATABASE: "database"
      MYSQL_USER: "user"
      MYSQL_PASSWORD: "password"
    ports:
      - '3306:3306'
  nginx-uwsgi-flask:
    restart: "always"
    depends_on:
      - "db"
    build:
      context: .
      dockerfile: ./docker/nginx-uwsgi-flask/Dockerfile
    volumes:
      - "~/data/fileshare:/fileshare"
    ports:
      - "80:80"
      - "443:443"
    network_mode: "host"

追溯

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1193, in _execute_context
    context)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 509, in do_execute
    cursor.execute(statement, parameters)
  File "/usr/local/lib/python3.6/site-packages/pymysql/cursors.py", line 170, in execute
    result = self._query(query)
  File "/usr/local/lib/python3.6/site-packages/pymysql/cursors.py", line 328, in _query
    conn.query(q)
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 517, in query
    self._affected_rows = self._read_query_result(unbuffered=unbuffered)
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 732, in _read_query_result
    result.read()
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 1075, in read
    first_packet = self.connection._read_packet()
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 657, in _read_packet
    packet_header = self._read_bytes(4)
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 707, in _read_bytes
    CR.CR_SERVER_LOST, "Lost connection to MySQL server during query")
pymysql.err.OperationalError: (2013, 'Lost connection to MySQL server during query')

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/usr/local/lib/python3.6/site-packages/flask_user/decorators.py", line 132, in decorator
    allowed = _is_logged_in_with_confirmed_email(user_manager)
  File "/usr/local/lib/python3.6/site-packages/flask_user/decorators.py", line 17, in _is_logged_in_with_confirmed_email
    if user_manager.call_or_get(current_user.is_authenticated):
  File "/usr/local/lib/python3.6/site-packages/werkzeug/local.py", line 347, in __getattr__
    return getattr(self._get_current_object(), name)
  File "/usr/local/lib/python3.6/site-packages/werkzeug/local.py", line 306, in _get_current_object
    return self.__local()
  File "/usr/local/lib/python3.6/site-packages/flask_login/utils.py", line 26, in <lambda>
    current_user = LocalProxy(lambda: _get_user())
  File "/usr/local/lib/python3.6/site-packages/flask_login/utils.py", line 335, in _get_user
    current_app.login_manager._load_user()
  File "/usr/local/lib/python3.6/site-packages/flask_login/login_manager.py", line 359, in _load_user
    return self.reload_user()
  File "/usr/local/lib/python3.6/site-packages/flask_login/login_manager.py", line 321, in reload_user
    user = self.user_callback(user_id)
  File "/usr/local/lib/python3.6/site-packages/flask_user/user_manager.py", line 130, in load_user_by_user_token
    user = self.db_manager.UserClass.get_user_by_token(user_token)
  File "/usr/local/lib/python3.6/site-packages/flask_user/user_mixin.py", line 51, in get_user_by_token
    user = user_manager.db_manager.get_user_by_id(user_id)
  File "/usr/local/lib/python3.6/site-packages/flask_user/db_manager.py", line 179, in get_user_by_id
    return self.db_adapter.get_object(self.UserClass, id=id)
  File "/usr/local/lib/python3.6/site-packages/flask_user/db_adapters/sql_db_adapter.py", line 48, in get_object
    return ObjectClass.query.get(id)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 924, in get
    ident, loading.load_on_pk_identity)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 1007, in _get_impl
    return db_load_fn(self, primary_key_identity)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 250, in load_on_pk_identity
    return q.one()
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2954, in one
    ret = self.one_or_none()
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2924, in one_or_none
    ret = list(self)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2995, in __iter__
    return self._execute_and_instances(context)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3018, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 948, in execute
    return meth(self, multiparams, params)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/sql/elements.py", line 269, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1060, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1200, in _execute_context
    context)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1413, in _handle_dbapi_exception
    exc_info
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 265, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 248, in reraise
    raise value.with_traceback(tb)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1193, in _execute_context
    context)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 509, in do_execute
    cursor.execute(statement, parameters)
  File "/usr/local/lib/python3.6/site-packages/pymysql/cursors.py", line 170, in execute
    result = self._query(query)
  File "/usr/local/lib/python3.6/site-packages/pymysql/cursors.py", line 328, in _query
    conn.query(q)
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 517, in query
    self._affected_rows = self._read_query_result(unbuffered=unbuffered)
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 732, in _read_query_result
    result.read()
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 1075, in read
    first_packet = self.connection._read_packet()
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 657, in _read_packet
    packet_header = self._read_bytes(4)
  File "/usr/local/lib/python3.6/site-packages/pymysql/connections.py", line 707, in _read_bytes
    CR.CR_SERVER_LOST, "Lost connection to MySQL server during query")
sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2013, 'Lost connection to MySQL server during query') [SQL: 'SELECT user.is_active AS user_is_active, user.id AS user_id, user.username AS user_username, user.password AS user_password, user.reset_password_token AS user_reset_password_token, user.email AS user_email, user.email_confirmed_at AS user_email_confirmed_at, user.first_name AS user_first_name, user.last_name AS user_last_name \nFROM user \nWHERE user.id = %(param_1)s'] [parameters: {'param_1': 13}] (Background on this error at: http://sqlalche.me/e/e3q8)

Answer 1

我通过从容器迁移mariadb到mysql. 我仍然不知道根本原因是什么。