mysql - docker-compose 未知 MySQL 服务器主机 'mysql'( Airflow )

Question

我尝试创建我的 Airflow 服务。当我分别运行三个 docker(没有 docker-compose)时，一切正常，但是当我尝试使用 docker-compose 做同样的事情时，我得到了错误。 Airflow 似乎没有看到数据库。

docker-compose.yml

version: '2'

services:

  mysql:
    image: "someregisty/mysql"
    environment:
     - MYSQL_ROOT_PASSWORD=somepassword

  redis:
    image: "someregisty/redis"

  airflow:
    image: "someregisty/airflow"
    volumes:
     - ./dags:/home/airflow/dags
     - ./logs:/home/airflow/logs
     - ./config/airflow.cfg:/home/airflow/airflow.cfg 
     - ./config/resolv.conf:/etc/resolv.conf
     - ./config/somekeytab.keytab:/home/airflow/airflow.keytab 
    ports:
     - "8484:8080"
    environment:
     - AIRFLOW__CELERY__BROKER_URL=redis://redis:6379/0
     - AIRFLOW__CELERY__CELERY_RESULT_BACKEND=db+mysql://root:somepassword@mysql/airflow
     - AIRFLOW__CORE__SQL_ALCHEMY_CONN=mysql://root:somepassword@mysql/airflow
     - AIRFLOW__CORE__AIRFLOW_HOME=/home/airflow
     - AIRFLOW__CORE__DAGS_FOLDER=/home/airflow/dags/
     - AIRFLOW__CORE__PLUGINS_FOLDER=/home/airflow/plugins/
     - AIRFLOW_SCHEDULER=true
     - AIRFLOW_WEBSERVER=true
     - AIRFLOW_WORKER=true
     - AIRFLOW_KERBEROS=true
     - AIRFLOW_KERBEROS_PRINCIPAL=prj_bdc@DCWP.PL
     - AIRFLOW__KERBEROS__CCACHE=/home/airflow/kerberos.keytab.cache
     - KRB5CCNAME=/home/airflow/kerberos.keytab.cache
    depends_on:
     - redis
     - mysql

我跑

docker-compose up -d
docker-compose exec mysql mysql -u root --password=somepassword -e "create database airflow"

这很好用。然后我跑

docker-compose exec airflow airflow initdb

我明白了

[2017-09-28 16:34:36,100] {__init__.py:57} INFO - Using executor CeleryExecutor
/usr/lib/python2.7/site-packages/airflow/utils/helpers.py:406: DeprecationWarning: Importing BaseSensorOperator directly from <module 'airflow.operators' from '/usr/lib/python2.7/site-packages/airflow/operators/__init__.pyc'> has been deprecated. Please import from '<module 'airflow.operators' from '/usr/lib/python2.7/site-packages/airflow/operators/__init__.pyc'>.[operator_module]' instead. Support for direct imports will be dropped entirely in Airflow 2.0.
  DeprecationWarning)
DB: mysql://root:***@mysql/airflow
[2017-09-28 16:34:36,666] {db.py:287} INFO - Creating tables
Traceback (most recent call last):
  File "/usr/bin/airflow", line 28, in <module>
    args.func(args)
  File "/usr/lib/python2.7/site-packages/airflow/bin/cli.py", line 951, in initdb
    db_utils.initdb()
  File "/usr/lib/python2.7/site-packages/airflow/utils/db.py", line 106, in initdb
    upgradedb()
  File "/usr/lib/python2.7/site-packages/airflow/utils/db.py", line 294, in upgradedb
    command.upgrade(config, 'heads')
  File "/usr/lib/python2.7/site-packages/alembic/command.py", line 174, in upgrade
    script.run_env()
  File "/usr/lib/python2.7/site-packages/alembic/script/base.py", line 416, in run_env
    util.load_python_file(self.dir, 'env.py')
  File "/usr/lib/python2.7/site-packages/alembic/util/pyfiles.py", line 93, in load_python_file
    module = load_module_py(module_id, path)
  File "/usr/lib/python2.7/site-packages/alembic/util/compat.py", line 79, in load_module_py
    mod = imp.load_source(module_id, path, fp)
  File "/usr/lib/python2.7/site-packages/airflow/migrations/env.py", line 86, in <module>
    run_migrations_online()
  File "/usr/lib/python2.7/site-packages/airflow/migrations/env.py", line 73, in run_migrations_online
    with connectable.connect() as connection:
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 2091, in connect
    return self._connection_cls(self, **kwargs)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 90, in __init__
    if connection is not None else engine.raw_connection()
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 2177, in raw_connection
    self.pool.unique_connection, _connection)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 2151, in _wrap_pool_connect
    e, dialect, self)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 1465, in _handle_dbapi_exception_noconnection
    exc_info
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/util/compat.py", line 203, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 2147, in _wrap_pool_connect
    return fn()
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/pool.py", line 328, in unique_connection
    return _ConnectionFairy._checkout(self)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/pool.py", line 766, in _checkout
    fairy = _ConnectionRecord.checkout(pool)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/pool.py", line 516, in checkout
    rec = pool._do_get()
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/pool.py", line 1138, in _do_get
    self._dec_overflow()
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/pool.py", line 1135, in _do_get
    return self._create_connection()
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/pool.py", line 333, in _create_connection
    return _ConnectionRecord(self)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/pool.py", line 461, in __init__
    self.__connect(first_connect_check=True)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/pool.py", line 651, in __connect
    connection = pool._invoke_creator(self)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/strategies.py", line 105, in connect
    return dialect.connect(*cargs, **cparams)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/default.py", line 393, in connect
    return self.dbapi.connect(*cargs, **cparams)
  File "/usr/lib64/python2.7/site-packages/MySQLdb/__init__.py", line 86, in Connect
    return Connection(*args, **kwargs)
  File "/usr/lib64/python2.7/site-packages/MySQLdb/connections.py", line 204, in __init__
    super(Connection, self).__init__(*args, **kwargs2)
sqlalchemy.exc.OperationalError: (_mysql_exceptions.OperationalError) (2005, "Unknown MySQL server host 'mysql' (0)")

我不知道出了什么问题。也许你能帮助我？ :)

docker 和 docker-compose 的版本是

Docker version 1.12.6, build 96d83a5/1.12.6
docker-compose version 1.9.0, build 2585387

Answer 1

问题是由于将 resolv.conf 文件绑定(bind)到 Airflow 容器中引起的。您从 Airflow 容器收到 unknown MySQL server host 'mysql' 错误的原因是 mysql 主机名无法解析为 Airflow 容器的 ip。

解决方案 1

从 Compose 配置中删除 ./config/resolv.conf:/etc/resolv.conf。它将导致 Docker 正确解析主机名。如果您需要指定额外的 DNS 服务器，请使用 Compose --dns 选项 documented here .

解决方案 2(不推荐)

将 nameserver 127.0.0.11 行添加到 /etc/resolv.conf 文件。它支持使用 Docker 嵌入式 DNS 服务器，这是默认设置。您也可以将自定义条目保存在该文件中。请注意，此解决方案是一种 hack，因为如文档中所述，Docker 负责管理 /etc/resolv.conf 文件。引用文档进行备份:

So you should not assume the way the files such as /etc/hosts, /etc/resolv.conf are managed inside the containers and leave the files alone and use the following Docker options instead

更多

您可以阅读有关 Docker embedded DNS server in user-defined networks here 的更多信息.