airflow-webserver-monitor.pid is already locked

증상

Airflow webserver, scheduler가 작동하지 않음

Error log

Traceback (most recent call last):
  File "/home/keti/.local/lib/python3.6/site-packages/lockfile/pidlockfile.py", line 77, in acquire
    write_pid_to_pidfile(self.path)
  File "/home/keti/.local/lib/python3.6/site-packages/lockfile/pidlockfile.py", line 161, in write_pid_to_pidfile
    pidfile_fd = os.open(pidfile_path, open_flags, open_mode)
FileExistsError: [Errno 17] File exists: '/home/keti/airflow/airflow-webserver-monitor.pid'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/keti/anaconda3/envs/airflow/bin/airflow", line 8, in <module>
    sys.exit(main())
  File "/home/keti/anaconda3/envs/airflow/lib/python3.6/site-packages/airflow/__main__.py", line 40, in main
    args.func(args)
  File "/home/keti/anaconda3/envs/airflow/lib/python3.6/site-packages/airflow/cli/cli_parser.py", line 48, in command
    return func(*args, **kwargs)
  File "/home/keti/anaconda3/envs/airflow/lib/python3.6/site-packages/airflow/utils/cli.py", line 91, in wrapper
    return f(*args, **kwargs)
  File "/home/keti/anaconda3/envs/airflow/lib/python3.6/site-packages/airflow/cli/commands/webserver_command.py", line 467, in webserver
    with ctx:
  File "/home/keti/anaconda3/envs/airflow/lib/python3.6/site-packages/daemon/daemon.py", line 389, in __enter__
    self.open()
  File "/home/keti/anaconda3/envs/airflow/lib/python3.6/site-packages/daemon/daemon.py", line 381, in open
    self.pidfile.__enter__()
  File "/home/keti/.local/lib/python3.6/site-packages/lockfile/__init__.py", line 197, in __enter__
    self.acquire()
  File "/home/keti/anaconda3/envs/airflow/lib/python3.6/site-packages/daemon/pidfile.py", line 57, in acquire
    super().acquire(timeout, *args, **kwargs)
  File "/home/keti/.local/lib/python3.6/site-packages/lockfile/pidlockfile.py", line 88, in acquire
    self.path)
lockfile.AlreadyLocked: /home/keti/airflow/airflow-webserver-monitor.pid is already locked

Solution

.pid 파일을 지워주기만 하면된다.

$ sudo rm airflow-scheduler.pid airflow-webserver-monitor.pid