Python使用Session发送请求预热链接的方法步骤

冷连接耗时 = TCP 三次握手(1 RTT) + TLS 握手(2 RTT) + 请求响应(1 RTT) = 4 RTT
热连接耗时 = 请求响应(1 RTT) = 1 RTT

import requests

s = requests.Session()

# 第一次：冷连接，TCP + TLS 全部握手，慢
s.get('https://api.example.com/data')

# 第二次：复用连接，快
s.get('https://api.example.com/data')

import requests

s = requests.Session()

# 预热：发一个 HEAD 请求，握手完成后连接留在池中
s.head('https://api.example.com/health')

# 后续请求直接复用，第一个请求也是热连接
resp = s.get('https://api.example.com/data')

import urllib3

pool = urllib3.PoolManager(num_pools=50, maxsize=20)

# 预热：强制建立到目标主机的连接，不发请求
pool.connection_from_host('api.example.com', port=443, scheme='https')

# 连接已就位，后续请求直接复用
resp = pool.request('GET', 'https://api.example.com/data')

import requests

s = requests.Session()

# 拿到 urllib3 的连接池
pool = s.mount('https://', requests.adapters.HTTPAdapter(pool_connections=20, pool_maxsize=20))

# 预热
pool.poolmanager.connection_from_host('api.example.com', port=443, scheme='https')

# 后续请求复用
resp = s.get('https://api.example.com/data')

import urllib3
from urllib3.util.retry import Retry

pool = urllib3.PoolManager(
    num_pools=100,
    maxsize=50,
    timeout=3.0,
    retries=Retry(total=3, backoff_factor=0.5),
    block=True,
)

# 核心服务列表
core_hosts = [
    ('api.example.com', 443),
    ('auth.example.com', 443),
    ('cdn.example.com', 443),
]

print("开始预热连接...")
for host, port in core_hosts:
    try:
        pool.connection_from_host(host, port=port, scheme='https')
        print(f"  ✅ {host}")
    except Exception as e:
        print(f"  ❌ {host}: {e}")

print("预热完成，开始处理请求...")
resp = pool.request('GET', 'https://api.example.com/data')

# 不预热
s.get('https://api.example.com/data')  # ~280ms，完整握手
s.get('https://api.example.com/data')  # ~110ms，Session Resumption

try:
    pool.connection_from_host('api.example.com', port=443, scheme='https')
except urllib3.exceptions.NewConnectionError:
    print("服务未启动，跳过预热")

import urllib3
from urllib3.util.retry import Retry

# 创建连接池
pool = urllib3.PoolManager(
    num_pools=100,
    maxsize=50,
    timeout=3.0,
    retries=Retry(total=3, backoff_factor=0.5),
    block=True,
)

# 启动时预热核心服务
core_hosts = ['api.example.com', 'auth.example.com', 'cdn.example.com']
for host in core_hosts:
    try:
        pool.connection_from_host(host, port=443, scheme='https')
    except Exception:
        pass  # 静默跳过

# 后续所有请求，第一次就是热连接
resp = pool.request('GET', 'https://api.example.com/data')

pool.connection_from_host('api.example.com', port=443, scheme='https')