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将Python脚本作为systemd服务运行,连接到InfluxDB会导致ConnectionError

[英]Running Python script as systemd service, connecting to InfluxDB results in ConnectionError

我正在将Shell脚本作为Ubuntu的systemd服务运行,以在启动时启动。 该脚本在内部执行一个Python脚本( python_simulator.py ),该脚本连接到InfluxDB(通过Python的influxdb软件包)。

Python脚本无法在启动时启动,并且检查日志表明这是由于连接到InfluxDB时出现了“ ConnectionError ”。 我将其解释为,可能在引导服务激活Python服务时未启动influxdb服务。 因此,我尝试通过influxdb.service ”中添加“ After ”和“ Wants ”来在服务中添加订单依赖项,这会在influxdb服务之后几秒钟激活Python服务。 但是,我仍然遇到相同的连接错误。

系统服务( myservice.service)如下所示:

[Unit]
Description= Python startup service.
After=influxdb.service
Wants=influxdb.service

[Service]
Type=forking
ExecStart=/bin/bash /home/test_user/Deploy/start.sh
ExecStop=/bin/bash /home/test_user/Deploy/stop.sh

[Install]
WantedBy=multi-user.target

Python脚本的日志文件( python_simulator.py)

Traceback (most recent call last):
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/connection.py", line 159, in _new_conn
    (self._dns_host, self.port), self.timeout, **extra_kw)
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/util/connection.py", line 80, in create_connection
    raise err
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/util/connection.py", line 70, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/connectionpool.py", line 600, in urlopen
    chunked=chunked)
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/connectionpool.py", line 354, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "/usr/lib/python3.6/http/client.py", line 1239, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/usr/lib/python3.6/http/client.py", line 1285, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/usr/lib/python3.6/http/client.py", line 1234, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/lib/python3.6/http/client.py", line 1026, in _send_output
    self.send(msg)
  File "/usr/lib/python3.6/http/client.py", line 964, in send
    self.connect()
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/connection.py", line 181, in connect
    conn = self._new_conn()
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/connection.py", line 168, in _new_conn
    self, "Failed to establish a new connection: %s" % e)
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPConnection object at 0x7f817d91b400>: Failed to establish a new connection: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/requests/adapters.py", line 449, in send
    timeout=timeout
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/connectionpool.py", line 638, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/urllib3/util/retry.py", line 399, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='localhost', port=8086): Max retries exceeded with url: /query?q=SHOW+DATABASES (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f817d91b400>: Failed to establish a new connection: [$

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "python_simulator.py", line 467, in <module>
    main(host=args.host, port=args.port)
  File "python_simulator.py", line 312, in main
    for db_dict in client.get_list_database():
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/influxdb/client.py", line 570, in get_list_database
    return list(self.query("SHOW DATABASES").get_points())
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/influxdb/client.py", line 416, in query
    expected_response_code=expected_response_code
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/influxdb/client.py", line 267, in request
    timeout=self._timeout
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/requests/sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/requests/sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "/home/test_user/Deploy/py_venv/lib/python3.6/site-packages/requests/adapters.py", line 516, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPConnectionPool(host='localhost', port=8086): Max retries exceeded with url: /query?q=SHOW+DATABASES (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f817d91b400>: Failed to establish a new connection$

最后,守护程序的阻塞树显示myservice.serviceinfluxdb.service之后执行:

 myservice.service +6.872s └─influxdb.service @11.344s └─network-online.target @11.337s └─NetworkManager-wait-online.service @4.706s +6.630s └─NetworkManager.service @3.940s +674ms └─dbus.service @3.914s └─basic.target @3.728s └─sockets.target @3.728s └─snapd.socket @3.722s +5ms └─sysinit.target @3.712s └─apparmor.service @3.276s +435ms └─local-fs.target @3.266s └─run-user-1000.mount @49.841s └─swap.target @3.160s └─dev-disk-by\\x2duuid-16e1b46a\\x2d79fc\\x2d4965\\x2d9932\\x2d8f589e9e7057.swap @3.132s +23ms └─dev-disk-by\\x2duuid-16e1b46a\\x2d79fc\\x2d4965\\x2d9932\\x2d8f589e9e7057.device @3.130s 

我不确定为什么仍然无法使用influxdb执行脚本(python_simulator.py)。 还有其他依赖性吗? myservice.service是否需要任何更改? 任何帮助将不胜感激。

编辑1:

原因可能是ConnectionRefusedError而不是ConnectionError ,这可能是因为当它连接到端口8086上的流入时,没有人在监听吗? 如果是这样,我如何将其置于依赖关系顺序中?

即使创建服务依赖项,您仍然可能会遇到问题(因为influxdb可能需要一段时间才能准备好接受连接,在此期间Python代码可能会启动)。 解决方案是:

  • 编写Python代码以在连接被拒绝时重试连接,或者
  • 配置systemd以在服务失败时重新启动服务。

在没有看到您的Python代码的情况下,很难建议第一个解决方案是什么样的,但是将您的设备配置为在发生故障时重新启动就像将以下内容添加到[Service]部分一样简单:

Restart=on-failure

您可以通过在systemd单元中添加一个小的Shell脚本来延迟Python代码的启动,直到influxdb准备就绪为止:

ExecStartPre=/bin/sh -c 'while ! curl -sf http://localhost:8086/ping; do sleep 1; done'

这将无限期循环(从而阻止服务启动),直到influxdb成功响应/ping端点为止。

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