会话管理
Crawl4AI 中的会话管理是一项强大功能，允许您在多个请求之间保持状态，特别适合处理复杂的多步骤爬取任务。它使您能够在连续操作和爬取中重复使用同一个浏览器标签页（或页面对象），这对于以下场景尤为有益：
- 在爬取前后执行 JavaScript 操作
- 更快地执行连续多次爬取，无需重复打开标签页或分配内存
注意： 此功能专为顺序工作流设计，不适用于并行操作。
基础会话使用
使用 BrowserConfig 和 CrawlerRunConfig 通过 session_id 保持状态：
from crawl4ai.async_configs import BrowserConfig, CrawlerRunConfig
async with AsyncWebCrawler() as crawler:
session_id = "my_session"
# 定义配置
config1 = CrawlerRunConfig(
url="https://example.com/page1", session_id=session_id
)
config2 = CrawlerRunConfig(
url="https://example.com/page2", session_id=session_id
)
# 首次请求
result1 = await crawler.arun(config=config1)
# 使用相同会话的后续请求
result2 = await crawler.arun(config=config2)
# 完成后清理
await crawler.crawler_strategy.kill_session(session_id)
动态内容与会话
以下是通过会话状态爬取 GitHub 多页提交记录的示例：
from crawl4ai.async_configs import CrawlerRunConfig
from crawl4ai import JsonCssExtractionStrategy
from crawl4ai.cache_context import CacheMode
async def crawl_dynamic_content():
url = "https://github.com/microsoft/TypeScript/commits/main"
session_id = "wait_for_session"
all_commits = []
js_next_page = """
const commits = document.querySelectorAll('li[data-testid="commit-row-item"] h4');
if (commits.length > 0) {
window.lastCommit = commits[0].textContent.trim();
}
const button = document.querySelector('a[data-testid="pagination-next-button"]');
if (button) {button.click(); console.log('button clicked') }
"""
wait_for = """() => {
const commits = document.querySelectorAll('li[data-testid="commit-row-item"] h4');
if (commits.length === 0) return false;
const firstCommit = commits[0].textContent.trim();
return firstCommit !== window.lastCommit;
}"""
schema = {
"name": "Commit Extractor",
"baseSelector": "li[data-testid='commit-row-item']",
"fields": [
{
"name": "title",
"selector": "h4 a",
"type": "text",
"transform": "strip",
},
],
}
extraction_strategy = JsonCssExtractionStrategy(schema, verbose=True)
browser_config = BrowserConfig(
verbose=True,
headless=False,
)
async with AsyncWebCrawler(config=browser_config) as crawler:
for page in range(3):
crawler_config = CrawlerRunConfig(
session_id=session_id,
css_selector="li[data-testid='commit-row-item']",
extraction_strategy=extraction_strategy,
js_code=js_next_page if page > 0 else None,
wait_for=wait_for if page > 0 else None,
js_only=page > 0,
cache_mode=CacheMode.BYPASS,
capture_console_messages=True,
)
result = await crawler.arun(url=url, config=crawler_config)
if result.console_messages:
print(f"Page {page + 1} console messages:", result.console_messages)
if result.extracted_content:
# print(f"Page {page + 1} result:", result.extracted_content)
commits = json.loads(result.extracted_content)
all_commits.extend(commits)
print(f"Page {page + 1}: Found {len(commits)} commits")
else:
print(f"Page {page + 1}: No content extracted")
print(f"Successfully crawled {len(all_commits)} commits across 3 pages")
# 清理会话
await crawler.crawler_strategy.kill_session(session_id)
示例1：基础会话爬取
使用会话爬取的简单示例：
import asyncio
from crawl4ai.async_configs import BrowserConfig, CrawlerRunConfig
from crawl4ai.cache_context import CacheMode
async def basic_session_crawl():
async with AsyncWebCrawler() as crawler:
session_id = "dynamic_content_session"
url = "https://example.com/dynamic-content"
for page in range(3):
config = CrawlerRunConfig(
url=url,
session_id=session_id,
js_code="document.querySelector('.load-more-button').click();" if page > 0 else None,
css_selector=".content-item",
cache_mode=CacheMode.BYPASS
)
result = await crawler.arun(config=config)
print(f"Page {page + 1}: Found {result.extracted_content.count('.content-item')} items")
await crawler.crawler_strategy.kill_session(session_id)
asyncio.run(basic_session_crawl())
此示例展示：
1. 在多个请求间复用相同的 session_id
2. 执行 JavaScript 动态加载更多内容
3. 正确关闭会话释放资源
高级技巧1：自定义执行钩子
警告：接下来的几个示例可能会让您感到困惑 😅，请确保您已熟悉前面的内容再继续。
使用自定义钩子处理复杂场景，例如等待动态内容加载：
async def advanced_session_crawl_with_hooks():
first_commit = ""
async def on_execution_started(page):
nonlocal first_commit
try:
while True:
await page.wait_for_selector("li.commit-item h4")
commit = await page.query_selector("li.commit-item h4")
commit = await commit.evaluate("(element) => element.textContent").strip()
if commit and commit != first_commit:
first_commit = commit
break
await asyncio.sleep(0.5)
except Exception as e:
print(f"Warning: New content didn't appear: {e}")
async with AsyncWebCrawler() as crawler:
session_id = "commit_session"
url = "https://github.com/example/repo/commits/main"
crawler.crawler_strategy.set_hook("on_execution_started", on_execution_started)
js_next_page = """document.querySelector('a.pagination-next').click();"""
for page in range(3):
config = CrawlerRunConfig(
url=url,
session_id=session_id,
js_code=js_next_page if page > 0 else None,
css_selector="li.commit-item",
js_only=page > 0,
cache_mode=CacheMode.BYPASS
)
result = await crawler.arun(config=config)
print(f"Page {page + 1}: Found {len(result.extracted_content)} commits")
await crawler.crawler_strategy.kill_session(session_id)
asyncio.run(advanced_session_crawl_with_hooks())
此技术确保新内容在下次操作前完成加载。
高级技巧2：集成JavaScript执行与等待
结合JavaScript执行和等待逻辑，简洁处理动态内容：
async def integrated_js_and_wait_crawl():
async with AsyncWebCrawler() as crawler:
session_id = "integrated_session"
url = "https://github.com/example/repo/commits/main"
js_next_page_and_wait = """
(async () => {
const getCurrentCommit = () => document.querySelector('li.commit-item h4').textContent.trim();
const initialCommit = getCurrentCommit();
document.querySelector('a.pagination-next').click();
while (getCurrentCommit() === initialCommit) {
await new Promise(resolve => setTimeout(resolve, 100));
}
})();
"""
for page in range(3):
config = CrawlerRunConfig(
url=url,
session_id=session_id,
js_code=js_next_page_and_wait if page > 0 else None,
css_selector="li.commit-item",
js_only=page > 0,
cache_mode=CacheMode.BYPASS
)
result = await crawler.arun(config=config)
print(f"Page {page + 1}: Found {len(result.extracted_content)} commits")
await crawler.crawler_strategy.kill_session(session_id)
asyncio.run(integrated_js_and_wait_crawl())
会话的常见用例
1. 认证流程：登录并与受保护页面交互
2. 分页处理：浏览多页内容
3. 表单提交：填写表单、提交并处理结果
4. 多步骤流程：完成跨多个操作的工作流
5. 动态内容导航：处理JavaScript渲染或事件触发的内容