无法启动 Airflow worker/flower，需要澄清 Airflow 架构以确认安装正确

Question

在不同的机器上运行工作器会导致下面指定的错误。我已关注the configuration instructions 并已同步 dags 文件夹。

我也想确认一下，RabbitMQ和PostgreSQL只需要安装在Airflow核心机器上，不需要安装在worker上（worker只连接核心）。

设置的详细说明如下：

Airflow 核心/服务器计算机

已安装以下内容：

• Python 2.7 与
  • 气流 (AIRFLOW_HOME = ~/airflow)
  • 芹菜
  • psycogp2
• RabbitMQ
• PostgreSQL

airflow.cfg 中的配置：

• sql_alchemy_conn = postgresql+psycopg2://username:password@192.168.1.2:5432/airflow
• executor = CeleryExecutor
• broker_url = amqp://username:password@192.168.1.2:5672//
• celery_result_backend = postgresql+psycopg2://username:password@192.168.1.2:5432/airflow

执行的测试：

• RabbitMQ 正在运行
• 可以连接到 PostgreSQL 并且已经确认 Airflow 已经创建了表
• 可以启动和查看网络服务器（包括自定义 dag）

.

.

气流工作者计算机

已安装以下内容：

• Python 2.7 与
  • 气流 (AIRFLOW_HOME = ~/airflow)
  • 芹菜
  • psycogp2

airflow.cfg 中的配置与服务器中的完全相同：

• sql_alchemy_conn = postgresql+psycopg2://username:password@192.168.1.2:5432/airflow
• executor = CeleryExecutor
• broker_url = amqp://username:password@192.168.1.2:5672//
• celery_result_backend = postgresql+psycopg2://username:password@192.168.1.2:5432/airflow

在工作机器上运行的命令的输出：

运行airflow flower时：

ubuntu@airflow_client:~/airflow$ airflow flower
[2016-06-13 04:19:42,814] {__init__.py:36} INFO - Using executor CeleryExecutor
Traceback (most recent call last):
  File "/home/ubuntu/anaconda2/bin/airflow", line 15, in <module>
    args.func(args)
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/airflow/bin/cli.py", line 576, in flower
    os.execvp("flower", ['flower', '-b', broka, port, api])
  File "/home/ubuntu/anaconda2/lib/python2.7/os.py", line 346, in execvp
    _execvpe(file, args)
  File "/home/ubuntu/anaconda2/lib/python2.7/os.py", line 382, in _execvpe
    func(fullname, *argrest)
OSError: [Errno 2] No such file or directory

运行airflow worker时：

ubuntu@airflow_client:~$ airflow worker
[2016-06-13 04:08:43,573] {__init__.py:36} INFO - Using executor CeleryExecutor
[2016-06-13 04:08:43,935: ERROR/MainProcess] Unrecoverable error: ImportError('No module named postgresql',)
Traceback (most recent call last):
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/celery/worker/__init__.py", line 206, in start
    self.blueprint.start(self)
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/celery/bootsteps.py", line 119, in start
    self.on_start()
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/celery/apps/worker.py", line 169, in on_start
    string(self.colored.cyan(' \n', self.startup_info())),
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/celery/apps/worker.py", line 230, in startup_info
    results=self.app.backend.as_uri(),
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/kombu/utils/__init__.py", line 325, in __get__
    value = obj.__dict__[self.__name__] = self.__get(obj)
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/celery/app/base.py", line 626, in backend
    return self._get_backend()
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/celery/app/base.py", line 444, in _get_backend
    self.loader)
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/celery/backends/__init__.py", line 68, in get_backend_by_url
    return get_backend_cls(backend, loader), url
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/celery/backends/__init__.py", line 49, in get_backend_cls
    cls = symbol_by_name(backend, aliases)
  File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/kombu/utils/__init__.py", line 96, in symbol_by_name
    module = imp(module_name, package=package, **kwargs)
  File "/home/ubuntu/anaconda2/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
ImportError: No module named postgresql

当celery_result_backend 更改为默认db+mysql://airflow:airflow@localhost:3306/airflow 并再次运行airflow worker 时，结果为：

ubuntu@airflow_client:~/airflow$ airflow worker                                                                             
[2016-06-13 04:17:32,387] {__init__.py:36} INFO - Using executor CeleryExecutor

 -------------- celery@airflow_client2 v3.1.23 (Cipater)
---- **** ----- 
--- * ***  * -- Linux-3.19.0-59-generic-x86_64-with-debian-jessie-sid
-- * - **** --- 
- ** ---------- [config]
- ** ---------- .> app:         airflow.executors.celery_executor:0x7f5cb65cb510
- ** ---------- .> transport:   amqp://username:**@192.168.1.2:5672//
- ** ---------- .> results:     mysql://airflow:**@localhost:3306/airflow
- *** --- * --- .> concurrency: 16 (prefork)
-- ******* ---- 
--- ***** ----- [queues]
 -------------- .> default          exchange=default(direct) key=celery


[2016-06-13 04:17:33,385] {__init__.py:36} INFO - Using executor CeleryExecutor
Starting flask
[2016-06-13 04:17:33,737] {_internal.py:87} INFO -  * Running on http://0.0.0.0:8793/ (Press CTRL+C to quit)
[2016-06-13 04:17:34,536: WARNING/MainProcess] celery@airflow_client2 ready.

我错过了什么？如何进一步诊断？

Answer 1

ImportError: No module named postgresql 错误是由于您的 celery_result_backend 中使用的前缀无效。当使用数据库作为 Celery 后端时，连接 URL 必须以 db+ 为前缀。看 https://docs.celeryproject.org/en/stable/userguide/configuration.html#conf-database-result-backend

所以替换：

celery_result_backend = postgresql+psycopg2://username:password@192.168.1.2:5432/airflow

类似：

celery_result_backend = db+postgresql://username:password@192.168.1.2:5432/airflow

Answer 2

您需要确保安装 Celery Flower。即pip install flower。