Python 为什么 AWS Lambda 使用 requests.get 对于无法解析的域会出现持续 10 秒的延迟

您看到的问题是由于AWS域名解析花费了长达10秒的时间.如果您想要更多地控制DNS解析，您可以实现一个自定义请求Transport Adapter来自己进行DNS解析-这允许您更好地自定义超时.

pip install dnspython

import urllib
import requests
import dns.resolver


class CustomDnsResolverHttpAdapter(requests.adapters.HTTPAdapter):
    def resolve(self, hostname):
        resolver = dns.resolver.Resolver(configure=False)
        resolver.timeout = 5
        resolver.lifetime = 5

        resolver.nameservers = [
            "1.1.1.1"  # cloudflare dns
            , "8.8.8.8" # google dns
            # , "169.254.78.1"  # aws dns
        ]

        answer = resolver.resolve(hostname, "A", lifetime=5)

        if len(answer) == 0:
            return None

        return str(answer[0])

    def send(self, request, **kwargs):
        connection_pool_kwargs = self.poolmanager.connection_pool_kw

        result = urllib.parse.urlparse(request.url)
        resolved_ip = self.resolve(result.hostname)

        if result.scheme == "https" and resolved_ip:
            request.url = request.url.replace(
                "https://" + result.hostname,
                "https://" + resolved_ip,
            )
            connection_pool_kwargs["server_hostname"] = result.hostname  # SNI
            connection_pool_kwargs["assert_hostname"] = result.hostname

            # overwrite the host header
            request.headers["Host"] = result.hostname
        else:
            # clear these headers if they were set in a previous TLS request
            connection_pool_kwargs.pop("server_hostname", None)
            connection_pool_kwargs.pop("assert_hostname", None)

            # overwrite the host header
            request.headers["Host"] = result.hostname

        return super(CustomDnsResolverHttpAdapter, self).send(request, **kwargs)



http_agent = requests.Session()
http_agent.mount("http://", CustomDnsResolverHttpAdapter())
http_agent.mount("https://", CustomDnsResolverHttpAdapter())

response = http_agent.get("https://benandjerry.com")