Python requests调用API报域名解析错误且进程因OOM被杀死问题求助

使用Python的requests库请求API的脚本由调度器每日执行一次，此前运行一切正常，近期运行时会抛出异常，且对应PID的Python进程会因OOM（内存不足）被系统杀死，暂无法判断问题是DNS解析故障导致还是内存不足直接导致，寻求排查思路与解决方案。

报错回溯信息 #

Traceback (most recent call last):
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/connection.py", line 170, in _new_conn
    (self._dns_host, self.port), self.timeout, **extra_kw
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/util/connection.py", line 73, in create_connection
    for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
  File "/usr/lib/python3.6/socket.py", line 745, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -3] Temporary failure in name resolution

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/connectionpool.py", line 706, in urlopen
    chunked=chunked,
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/connectionpool.py", line 382, in _make_request
    self._validate_conn(conn)
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/connectionpool.py", line 1010, in _validate_conn
    conn.connect()
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/connection.py", line 353, in connect
    conn = self._new_conn()
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/connection.py", line 182, in _new_conn
    self, "Failed to establish a new connection: %s" % e
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPSConnection object at 0x7f163156c160>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/ubuntu/.local/lib/python3.6/site-packages/requests/adapters.py", line 449, in send
    timeout=timeout
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/connectionpool.py", line 756, in urlopen
    method, url, error=e, _pool=self, _stacktrace=sys.exc_info()[2]
  File "/home/ubuntu/.local/lib/python3.6/site-packages/urllib3/util/retry.py", line 574, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='<.............>', port=443): Max retries exceeded with url: /api/v2/test_connection/ (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f163156c160>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/ubuntu/pf_cic_etl_script_v2.py", line 50, in <module>
    resp = requests.get(url, headers=headers)
  File "/home/ubuntu/.local/lib/python3.6/site-packages/requests/api.py", line 76, in get
    return request('get', url, params=params, **kwargs)
  File "/home/ubuntu/.local/lib/python3.6/site-packages/requests/api.py", line 61, in request
    return session.request(method=method, url=url, **kwargs)
  File "/home/ubuntu/.local/lib/python3.6/site-packages/requests/sessions.py", line 542, in request
    resp = self.send(prep, **send_kwargs)
  File "/home/ubuntu/.local/lib/python3.6/site-packages/requests/sessions.py", line 655, in send
    r = adapter.send(request, **kwargs)
  File "/home/ubuntu/.local/lib/python3.6/site-packages/requests/adapters.py", line 516, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPSConnectionPool(host='<...............>', port=443): Max retries exceeded with url: /api/v2/test_connection/ (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f163156c160>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',))
Killed

进程被杀死系统日志 #

dmesg -T| grep -E -i -B100 'killed process'
[Sat Sep 25 06:08:31 2021] Tasks state (memory values in pages):
[Sat Sep 25 06:08:31 2021] [  pid  ]   uid  tgid total_vm      rss pgtables_bytes swapents oom_score_adj name
[Sat Sep 25 06:08:31 2021] [   1643]  1000  1643   517804   455512  4157440        0             0 python3
[Sat Sep 25 06:08:31 2021] [   1651]     0  1651     5954       69    86016        0             0 apport
[Sat Sep 25 06:08:31 2021] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=/,mems_allowed=0,global_oom,task_memcg=/user.slice,task=python3,pid=1643,uid=1000
[Sat Sep 25 06:08:31 2021] Out of memory: Killed process 1643 (python3) total-vm:2071216kB, anon-rss:1822048kB, file-rss:0kB, shmem-rss:0kB, UID:1000 pgtables:4060kB oom_score_adj:0

首先明确：DNS解析故障和OOM是两个独立存在的问题，前者是请求阶段抛出的业务异常，后者是进程占用内存超出系统阈值被强制终止的系统事件，两者无直接因果关系。

DNS解析问题排查 #

• 手动验证服务器DNS可用性：执行nslookup 你的API域名或ping 你的API域名，确认是否能正常解析到IP，依次排查/etc/resolv.conf配置是否错误、上游DNS服务器是否宕机、服务器网络策略是否限制了DNS请求
• 临时在/etc/hosts中绑定API域名和对应IP，重新运行脚本观察是否还会报解析错误，快速确认问题根因
• 脚本层面添加DNS解析异常捕获逻辑，遇到解析错误直接终止进程，避免后续无效逻辑占用内存资源

OOM内存溢出问题排查 #

• 从dmesg日志可看出Python进程运行时占用了近1.8G物理内存，先排查脚本逻辑：是否存在请求返回的响应体过大未及时释放、循环加载大量数据到内存不释放、内存泄漏等问题
• 使用memory_profiler工具逐行检测脚本内存占用，定位内存飙升的具体代码位置
• 代码优化：如果接口返回大体积响应，添加stream=True参数流式下载，避免一次性加载整个响应到内存；处理完的数据及时释放引用，不要长期存放在全局变量中
• 临时兜底方案：给脚本添加cgroup内存限制，或在调度执行前先检查系统可用内存，不足时延后执行，避免触发系统OOM杀死进程影响其他服务

额外优化建议 #

• 给requests请求配置合理的超时时间和重试次数，避免请求 hang 住长期占用资源，示例配置：requests.get(url, headers=headers, timeout=10)，重试逻辑可通过requests.adapters.HTTPAdapter配置
• 脚本执行时添加日志输出，记录每一步的内存占用和执行状态，方便后续出现问题时快速定位

内容的提问来源于stack exchange，提问作者Divyank