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python - OSError：[Errno 99] 无法分配请求的地址：flask、python 和 docker

问题描述

我有一个 python flask web 应用程序，它使用一个正在开发中的 python 库，我想 dockerize。这个图书馆发送 SPARQL 查询来搜索可用的书籍，从古腾堡项目获得的书籍收藏。此数据以 RDF 格式存储在 Fuseki 服务器中。Fuseki 服务器通过 docker 单独运行，查询的 SPARQL 端点如下：http://localhost:3030/gutenberg/sparql

使用以下 Docker 文件对 Web 应用进行 docker 化

FROM python:3.8-buster

RUN apt-get update
RUN apt-get install -y git

RUN apt-get install -y \
        apt-transport-https \
        ca-certificates \
        curl \
        gnupg2 \
        software-properties-common
COPY requirements.txt /app/requirements.txt
WORKDIR /app

RUN pip3 install -r requirements.txt

COPY . /app

CMD celery -A webapp.app.celery worker  --loglevel=DEBUG
CMD export FLASK_APP=wsgi.py

EXPOSE 80

ENTRYPOINT [ "python" ]

CMD [ "webapp/app.py" ]

使用以下命令：docker build -t wedh-dhtk-test .

构建 docker 映像后，我使用以下命令运行它：docker run --rm -p 80:80 wedh-dhtk-test

我遇到的问题是运行 Web 应用程序的 docker 容器似乎无法连接到 SPARQL 端点，并向我抛出以下两条错误消息：

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/urllib/request.py", line 1354, in do_open
    h.request(req.get_method(), req.selector, req.data, headers,
  File "/usr/local/lib/python3.8/http/client.py", line 1252, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/usr/local/lib/python3.8/http/client.py", line 1298, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/usr/local/lib/python3.8/http/client.py", line 1247, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/local/lib/python3.8/http/client.py", line 1007, in _send_output
    self.send(msg)
  File "/usr/local/lib/python3.8/http/client.py", line 947, in send
    self.connect()
  File "/usr/local/lib/python3.8/http/client.py", line 918, in connect
    self.sock = self._create_connection(
  File "/usr/local/lib/python3.8/socket.py", line 808, in create_connection
    raise err
  File "/usr/local/lib/python3.8/socket.py", line 796, in create_connection
    sock.connect(sa)
OSError: [Errno 99] Cannot assign requested address

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "webapp/app.py", line 16, in <module>
    AUTHORS = gd.get(what="author", name="all")
  File "/usr/local/lib/python3.8/site-packages/dhtk/extensions/gutenberg/__init__.py", line 98, in get
    response = self.wrapper.all_authors()
  File "/usr/local/lib/python3.8/site-packages/dhtk/extensions/gutenberg/api/data.py", line 387, in all_authors
    return [result["author"] for result in self._get_query_results(query)]
  File "/usr/local/lib/python3.8/site-packages/dhtk/extensions/gutenberg/api/data.py", line 789, in _get_query_results
    query_results = sparql.queryAndConvert()
  File "/usr/local/lib/python3.8/site-packages/SPARQLWrapper/Wrapper.py", line 1114, in queryAndConvert
    res = self.query()
  File "/usr/local/lib/python3.8/site-packages/SPARQLWrapper/Wrapper.py", line 1107, in query
    return QueryResult(self._query())
  File "/usr/local/lib/python3.8/site-packages/SPARQLWrapper/Wrapper.py", line 1073, in _query
    response = urlopener(request)
  File "/usr/local/lib/python3.8/urllib/request.py", line 222, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/local/lib/python3.8/urllib/request.py", line 525, in open
    response = self._open(req, data)
  File "/usr/local/lib/python3.8/urllib/request.py", line 542, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
  File "/usr/local/lib/python3.8/urllib/request.py", line 502, in _call_chain
    result = func(*args)
  File "/usr/local/lib/python3.8/urllib/request.py", line 1383, in http_open
    return self.do_open(http.client.HTTPConnection, req)
  File "/usr/local/lib/python3.8/urllib/request.py", line 1357, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [Errno 99] Cannot assign requested address>

环顾四周，我发现以下问题有同样的错误，即socket.error:[errno 99] cannot assign requested address在 docker 容器中运行烧瓶应用程序。问题已解决，将烧瓶 IP 地址设置为

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=80)

并在 Docker 文件上配置一个端口，我这样做了（回忆一下 Docker 文件的第 22 行EXPOSE 80）。

我的猜测是，其他设备（即 Fuseki 服务器）无法访问我运行我的应用程序的 docker 容器，但我找不到原因，并且我已经用尽了找出的方法。

标签： pythondockerflask

解决方案

我找到了这个问题的答案。正如@Christopher 所说，问题在于容器试图从内部访问我在 localhost:3000 上的 Fuseki 服务器，而它位于主机上。为了解决这个问题，我在 docker run 命令中添加了以下参数--net="host"并删除了-p 80:80. 完整的 docker run 命令如下所示

docker run --rm --net="host" wedh-dhtk-test

如果我理解正确，它允许我的 docker 容器指向服务器所在的 docker 主机。无论如何，它解决了我的问题，因为容器化应用程序现在正在按预期与 Fuseki 服务器通信。

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