Curl命令转Python requests脚本报错求助：无法建立连接

原Curl命令 #

export NEXRAN_XAPP=`sudo kubectl get svc -n ricxapp --field-selector metadata.name=service-ricxapp-nexran-rmr -o jsonpath='{.items[0].spec.clusterIP}'`

curl -i -X PUT -H "Content-type: application/json" -d '{"allocation_policy":{"type":"proportional","share":1024}}' http://${NEXRAN_XAPP}:8000/v1/slices/slow

curl -i -X PUT -H "Content-type: application/json" -d '{"allocation_policy":{"type":"proportional","share":256}}' http://${NEXRAN_XAPP}:8000/v1/slices/fast

错误的Python脚本 #

import requests
import os

os.system ("export NEXRAN_XAPP=`kubectl get svc -n ricxapp --field-selector metadata.name=service-ricxapp-nexran-rmr -o jsonpath='{.items[0].spec.clusterIP}'`")

headers = {
    'Content-type': 'application/json',
}

data1 = '{"allocation_policy":{"type":"proportional","share":1024}}'

data2 = '{"allocation_policy":{"type":"proportional","share":256}}'

response1 = requests.put('http://${NEXRAN_XAPP}:8000/v1/slices/fast', headers=headers, data=data1)

response2 = requests.put('http://${NEXRAN_XAPP}:8000/v1/slices/slow', headers=headers, data=data2)

报错信息 #

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 159, in _new_conn
    conn = connection.create_connection(
  File "/usr/lib/python3/dist-packages/urllib3/util/connection.py", line 61, in create_connection
    for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
  File "/usr/lib/python3.8/socket.py", line 918, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -2] Name or service not known

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 665, in urlopen
    httplib_response = self._make_request(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 387, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "/usr/lib/python3.8/http/client.py", line 1256, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1302, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1251, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1011, in _send_output
    self.send(msg)
  File "/usr/lib/python3.8/http/client.py", line 951, in send
    self.connect()
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 187, in connect
    conn = self._new_conn()
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 171, in _new_conn
    raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPConnection object at 0x7f2a6b15ec40>: Failed to establish a new connection: [Errno -2] Name or service not known

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/requests/adapters.py", line 439, in send
    resp = conn.urlopen(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 719, in urlopen
    retries = retries.increment(
  File "/usr/lib/python3/dist-packages/urllib3/util/retry.py", line 436, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='$%7bnexran_xapp%7d', port=8000): Max retries exceeded with url: /v1/slices/fast (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f2a6b15ec40>: Failed to establish a new connection: [Errno -2] Name or service not known'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "change_slice_allocation.py", line 14, in <module>
    response1 = requests.put('http://${NEXRAN_XAPP}:8000/v1/slices/fast', headers=headers, data=data1)
  File "/usr/lib/python3/dist-packages/requests/api.py", line 131, in put
    return request('put', url, data=data, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/api.py", line 60, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/adapters.py", line 516, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPConnectionPool(host='$%7bnexran_xapp%7d', port=8000): Max retries exceeded with url: /v1/slices/fast (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f2a6b15ec40>: Failed to establish a new connection: [Errno -2] Name or service not known'))

问题分析与修复 #

核心问题 #

1. os.system无法传递环境变量到Python进程：通过os.system执行的export命令仅在子shell中生效，Python主进程无法读取到NEXRAN_XAPP变量。
2. Python字符串不解析shell变量：代码中的'http://${NEXRAN_XAPP}:8000/...'是普通字符串，Python不会将${NEXRAN_XAPP}替换为实际IP，导致请求地址变成无效的$%7bnexran_xapp%7d。
3. JSON数据传递方式不够规范：直接传递字符串data虽然可行，但使用json参数更简洁，requests会自动设置正确的Content-Type头。

修复后的脚本 #

import requests
import subprocess

# 获取NEXRAN_XAPP的ClusterIP，用subprocess捕获命令输出
result = subprocess.run(
    ["sudo", "kubectl", "get", "svc", "-n", "ricxapp", 
     "--field-selector", "metadata.name=service-ricxapp-nexran-rmr", 
     "-o", "jsonpath='{.items[0].spec.clusterIP}'"],
    capture_output=True,
    text=True
)
# 处理输出，去掉多余的单引号
nexran_xapp_ip = result.stdout.strip().strip("'")

# 定义请求数据（用Python字典，方便维护）
payload_slow = {
    "allocation_policy": {
        "type": "proportional",
        "share": 1024
    }
}

payload_fast = {
    "allocation_policy": {
        "type": "proportional",
        "share": 256
    }
}

# 发送PUT请求，用json参数自动处理序列化和头部
response_slow = requests.put(f"http://{nexran_xapp_ip}:8000/v1/slices/slow", json=payload_slow)
response_fast = requests.put(f"http://{nexran_xapp_ip}:8000/v1/slices/fast", json=payload_fast)

# 可选：打印响应信息
print(f"Slow slice response: {response_slow.status_code}")
print(f"Fast slice response: {response_fast.status_code}")

关键改进点 #

• 使用subprocess.run替代os.system，直接捕获kubectl命令的输出结果，无需依赖环境变量传递。
• 用Python字典定义请求数据，通过json参数传给requests，自动完成JSON序列化和Content-Type头设置。
• 使用f-string格式化URL，将获取到的IP地址正确插入到请求路径中。
• 保留原Curl中的sudo（如果执行脚本需要权限的话），避免权限问题。

内容的提问来源于stack exchange，提问作者Black Dagger