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

我正在运行一个shell脚本作为Ubuntu的systemd服务，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包）

Python脚本无法在启动时启动，检查日志表明这是因为在连接XDB时出现了“ConnectionError”。我将其解释为，在启动时Python服务激活时，XDB服务可能没有启动。因此，我尝试在服务中添加订单依赖项，方法是将“在之后”和“想要”添加为“influxdb.service”，它在influxdb服务几秒钟后激活Python服务。但是，我仍然得到相同的连接错误

systemd服务（myservice.service）看起来像：

[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\u 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$

我不确定为什么我仍然无法在XDB就绪的情况下执行脚本（python_simulator.py）。还有其他依赖项吗？myservice.service中是否需要任何更改？任何帮助都将不胜感激

编辑1:

---

原因可能是ConnectionRefusedError而不是ConnectionError，这可能是因为当它连接到8086端口的流入时，没有任何东西在监听它？如果是这样，我如何将其按依赖关系顺序排列？

即使创建了服务依赖关系，也可能会遇到问题（因为XDB可能需要一段时间才能接受连接，在此期间Python代码可能会启动）。解决办法是：

• 编写Python代码，以便在连接被拒绝或中断时重试连接
• 配置systemd以在服务失败时重新启动服务

如果看不到Python代码，很难建议第一个解决方案是什么样子的，但是配置单元以在出现故障时重新启动非常简单，只需将以下内容添加到

[Service]

部分即可：

Restart=on-failure

---

通过向systemd单元添加一个小的shell脚本，可以延迟Python代码的启动，直到XDB准备就绪：

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

---

这将无限期地循环（从而阻止服务启动），直到influxdb成功响应

/ping

端点。

作为systemd服务运行的shell脚本执行Python脚本和其他一些操作。即使python脚本失败，其状态也始终为活动（正在运行）。有没有可能让systemd服务等到端口8086出现？我在答案中添加了一个可能的解决方案，尽管我认为前两个建议中的任何一个都会更好（因为如果在Python代码已经运行之后必须重新启动XDB服务，会发生什么情况？）我同意将systemd配置为在出现故障时重新启动是一个更好的解决方案。但正如我所说，执行.py时出错不会导致.sh服务失败，因此它不会重新启动。不过，等待端口8086的解决方案工作得很好。为了检查xdb停止时会发生什么，它实际上也停止了myservice。我假设这是因为我在myservice.service下有xdb.service。尽管如此，我还是希望它能像我所说的“restart=on failure”（可能是因为它“死了，没有失败”）那样重新启动，多亏了这一点。然而（我还没有深入调查过），在我将

TimeoutSec=360

添加到装置和ping中之前，这对我来说是行不通的。另见：

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