feat(crawl4ai): Implement SMART cache mode
This commit introduces a new cache mode, SMART, to the crawl4ai library. The SMART mode intelligently validates cached content using HEAD requests before using it, saving significant bandwidth while ensuring fresh content. The changes include modifications to the async_webcrawler.py, cache_context.py, and utils.py files in the crawl4ai directory. The async_webcrawler.py file now includes a check for the SMART cache mode and performs a HEAD check to see if the content has changed. If the content has changed, the url is re-crawled; otherwise, the cached result is used. The cache_context.py and utils.py files have been updated to support these changes. The documentation has also been updated to reflect these changes. The cache-modes.md file now includes a detailed explanation of the SMART mode, its logs, limitations, and an advanced example. The examples.md file now includes a link to the SMART Cache Mode example. The quickstart.md file now mentions the SMART mode in the note about cache modes. These changes improve the efficiency of the crawl4ai library by reducing unnecessary re-crawling and bandwidth usage. BREAKING CHANGE: The introduction of the SMART cache mode may affect existing code that uses the crawl4ai library and does not expect this new mode. Users should review the updated documentation to understand how to use this new mode.
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UncleCode
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docs/examples/smart_cache.py
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docs/examples/smart_cache.py
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"""
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SMART Cache Mode Example for Crawl4AI
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This example demonstrates how to use the SMART cache mode to intelligently
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validate cached content before using it. SMART mode can save 70-95% bandwidth
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on unchanged content while ensuring you always get fresh data when it changes.
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SMART Cache Mode: Only Crawl When Changes
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"""
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import sys
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import os
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sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '../..')))
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import asyncio
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import time
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from crawl4ai import AsyncWebCrawler
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from crawl4ai.cache_context import CacheMode
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from crawl4ai.async_configs import CrawlerRunConfig
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async def basic_smart_cache_example():
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"""Basic example showing SMART cache mode in action"""
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print("=== Basic SMART Cache Example ===\n")
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async with AsyncWebCrawler(verbose=True) as crawler:
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url = "https://example.com"
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# First crawl: Cache the content
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print("1. Initial crawl to cache the content:")
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config = CrawlerRunConfig(cache_mode=CacheMode.ENABLED)
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result1 = await crawler.arun(url=url, config=config)
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print(f" Initial crawl: {len(result1.html)} bytes\n")
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# Second crawl: Use SMART mode
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print("2. SMART mode crawl (should use cache for static content):")
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smart_config = CrawlerRunConfig(cache_mode=CacheMode.SMART)
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start_time = time.time()
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result2 = await crawler.arun(url=url, config=smart_config)
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elapsed = time.time() - start_time
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print(f" SMART crawl: {len(result2.html)} bytes in {elapsed:.2f}s")
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print(f" Content identical: {result1.html == result2.html}\n")
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async def news_site_monitoring():
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"""Monitor a news site for changes using SMART cache mode"""
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print("=== News Site Monitoring Example ===\n")
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async with AsyncWebCrawler(verbose=True) as crawler:
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config = CrawlerRunConfig(cache_mode=CacheMode.SMART)
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url = "https://news.ycombinator.com"
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print("Monitoring Hacker News for changes...\n")
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previous_length = 0
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for i in range(3):
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result = await crawler.arun(url=url, config=config)
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current_length = len(result.html)
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if i == 0:
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print(f"Check {i+1}: Initial crawl - {current_length} bytes")
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else:
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if current_length != previous_length:
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print(f"Check {i+1}: Content changed! {previous_length} -> {current_length} bytes")
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else:
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print(f"Check {i+1}: Content unchanged - {current_length} bytes")
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previous_length = current_length
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if i < 2: # Don't wait after last check
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print(" Waiting 10 seconds before next check...")
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await asyncio.sleep(10)
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print()
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async def compare_cache_modes():
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"""Compare different cache modes to understand SMART mode benefits"""
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print("=== Cache Mode Comparison ===\n")
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async with AsyncWebCrawler(verbose=False) as crawler:
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url = "https://www.wikipedia.org"
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# First, populate the cache
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config = CrawlerRunConfig(cache_mode=CacheMode.ENABLED)
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await crawler.arun(url=url, config=config)
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print("Cache populated.\n")
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# Test different cache modes
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modes = [
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(CacheMode.ENABLED, "ENABLED (always uses cache if available)"),
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(CacheMode.BYPASS, "BYPASS (never uses cache)"),
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(CacheMode.SMART, "SMART (validates cache before using)")
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]
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for mode, description in modes:
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config = CrawlerRunConfig(cache_mode=mode)
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start_time = time.time()
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result = await crawler.arun(url=url, config=config)
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elapsed = time.time() - start_time
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print(f"{description}:")
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print(f" Time: {elapsed:.2f}s")
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print(f" Size: {len(result.html)} bytes\n")
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async def dynamic_content_example():
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"""Show how SMART mode handles dynamic content"""
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print("=== Dynamic Content Example ===\n")
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async with AsyncWebCrawler(verbose=True) as crawler:
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# URL that returns different content each time
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dynamic_url = "https://httpbin.org/uuid"
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print("Testing with dynamic content (changes every request):\n")
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# First crawl
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config = CrawlerRunConfig(cache_mode=CacheMode.ENABLED)
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result1 = await crawler.arun(url=dynamic_url, config=config)
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# Extract UUID from the response
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import re
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uuid1 = re.search(r'"uuid":\s*"([^"]+)"', result1.html)
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if uuid1:
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print(f"1. First crawl UUID: {uuid1.group(1)}")
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# SMART mode crawl - should detect change and re-crawl
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smart_config = CrawlerRunConfig(cache_mode=CacheMode.SMART)
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result2 = await crawler.arun(url=dynamic_url, config=smart_config)
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uuid2 = re.search(r'"uuid":\s*"([^"]+)"', result2.html)
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if uuid2:
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print(f"2. SMART crawl UUID: {uuid2.group(1)}")
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print(f" Different UUIDs: {uuid1.group(1) != uuid2.group(1)} (should be True)")
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async def bandwidth_savings_demo():
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"""Demonstrate bandwidth savings with SMART mode"""
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print("=== Bandwidth Savings Demo ===\n")
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async with AsyncWebCrawler(verbose=True) as crawler:
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# List of URLs to crawl
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urls = [
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"https://example.com",
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"https://www.python.org",
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"https://docs.python.org/3/",
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]
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print("Crawling multiple URLs twice to show bandwidth savings:\n")
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# First pass: Cache all URLs
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print("First pass - Caching all URLs:")
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total_bytes_pass1 = 0
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config = CrawlerRunConfig(cache_mode=CacheMode.ENABLED)
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for url in urls:
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result = await crawler.arun(url=url, config=config)
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total_bytes_pass1 += len(result.html)
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print(f" {url}: {len(result.html)} bytes")
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print(f"\nTotal downloaded in first pass: {total_bytes_pass1} bytes")
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# Second pass: Use SMART mode
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print("\nSecond pass - Using SMART mode:")
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total_bytes_pass2 = 0
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smart_config = CrawlerRunConfig(cache_mode=CacheMode.SMART)
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for url in urls:
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result = await crawler.arun(url=url, config=smart_config)
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# In SMART mode, unchanged content uses cache (minimal bandwidth)
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print(f" {url}: Using {'cache' if result else 'fresh crawl'}")
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print(f"\nBandwidth saved: ~{total_bytes_pass1} bytes (only HEAD requests sent)")
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async def main():
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"""Run all examples"""
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examples = [
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basic_smart_cache_example,
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news_site_monitoring,
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compare_cache_modes,
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dynamic_content_example,
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bandwidth_savings_demo
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]
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for example in examples:
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await example()
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print("\n" + "="*50 + "\n")
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await asyncio.sleep(2) # Brief pause between examples
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if __name__ == "__main__":
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print("""
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Crawl4AI SMART Cache Mode Examples
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==================================
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These examples demonstrate the SMART cache mode that intelligently
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validates cached content using HEAD requests before deciding whether
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to use cache or perform a fresh crawl.
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""")
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asyncio.run(main())
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@@ -19,6 +19,7 @@ The new system uses a single `CacheMode` enum:
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- `CacheMode.READ_ONLY`: Only read from cache
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- `CacheMode.WRITE_ONLY`: Only write to cache
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- `CacheMode.BYPASS`: Skip cache for this operation
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- `CacheMode.SMART`: **NEW** - Intelligently validate cache with HEAD requests
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## Migration Example
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@@ -72,4 +73,128 @@ if __name__ == "__main__":
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| `bypass_cache=True` | `cache_mode=CacheMode.BYPASS` |
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| `disable_cache=True` | `cache_mode=CacheMode.DISABLED`|
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| `no_cache_read=True` | `cache_mode=CacheMode.WRITE_ONLY` |
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| `no_cache_write=True` | `cache_mode=CacheMode.READ_ONLY` |
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| `no_cache_write=True` | `cache_mode=CacheMode.READ_ONLY` |
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## SMART Cache Mode: Only Crawl When Changes
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Starting from version 0.7.1, Crawl4AI introduces the **SMART cache mode** - an intelligent caching strategy that validates cached content before using it. This mode uses HTTP HEAD requests to check if content has changed, potentially saving 70-95% bandwidth on unchanged content.
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### How SMART Mode Works
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When you use `CacheMode.SMART`, Crawl4AI:
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1. **Retrieves cached content** (if available)
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2. **Sends a HEAD request** with conditional headers (ETag, Last-Modified)
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3. **Validates the response**:
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- If server returns `304 Not Modified` → uses cache
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- If content changed → performs fresh crawl
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- If headers indicate changes → performs fresh crawl
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### Benefits
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- **Bandwidth Efficient**: Only downloads full content when necessary
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- **Always Fresh**: Ensures you get the latest content when it changes
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- **Cost Effective**: Reduces API calls and bandwidth usage
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- **Intelligent**: Uses multiple signals to detect changes (ETag, Last-Modified, Content-Length)
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### Basic Usage
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```python
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import asyncio
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from crawl4ai import AsyncWebCrawler
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from crawl4ai.cache_context import CacheMode
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from crawl4ai.async_configs import CrawlerRunConfig
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async def smart_crawl():
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async with AsyncWebCrawler(verbose=True) as crawler:
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# First crawl - caches the content
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config = CrawlerRunConfig(cache_mode=CacheMode.ENABLED)
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result1 = await crawler.arun(
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url="https://example.com",
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config=config
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)
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print(f"First crawl: {len(result1.html)} bytes")
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# Second crawl - uses SMART mode
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smart_config = CrawlerRunConfig(cache_mode=CacheMode.SMART)
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result2 = await crawler.arun(
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url="https://example.com",
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config=smart_config
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)
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print(f"SMART crawl: {len(result2.html)} bytes (from cache if unchanged)")
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asyncio.run(smart_crawl())
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```
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### When to Use SMART Mode
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SMART mode is ideal for:
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- **Periodic crawling** of websites that update irregularly
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- **News sites** where you want fresh content but avoid re-downloading unchanged pages
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- **API endpoints** that provide proper caching headers
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- **Large-scale crawling** where bandwidth costs are significant
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### How It Detects Changes
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SMART mode checks these signals in order:
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1. **304 Not Modified** status (most reliable)
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2. **Content-Digest** header (RFC 9530)
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3. **Strong ETag** comparison
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4. **Last-Modified** timestamp
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5. **Content-Length** changes (as a hint)
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### Example: News Site Monitoring
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```python
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async def monitor_news_site():
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async with AsyncWebCrawler(verbose=True) as crawler:
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config = CrawlerRunConfig(cache_mode=CacheMode.SMART)
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# Check multiple times
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for i in range(3):
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result = await crawler.arun(
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url="https://news.ycombinator.com",
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config=config
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)
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# SMART mode will only re-crawl if content changed
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print(f"Check {i+1}: Retrieved {len(result.html)} bytes")
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await asyncio.sleep(300) # Wait 5 minutes
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asyncio.run(monitor_news_site())
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```
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### Understanding SMART Mode Logs
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When using SMART mode with `verbose=True`, you'll see informative logs:
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```
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[SMART] ℹ SMART cache: 304 Not Modified - Content unchanged - Using cache for https://example.com
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[SMART] ℹ SMART cache: Content-Length changed (12345 -> 12789) - Re-crawling https://example.com
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[SMART] ℹ SMART cache: No definitive cache headers matched - Assuming content changed - Re-crawling https://example.com
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```
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### Limitations
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- Some servers don't properly support HEAD requests
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- Dynamic content without proper cache headers will always be re-crawled
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- Content changes must be reflected in HTTP headers for detection
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### Advanced Example
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For a complete example demonstrating SMART mode with both static and dynamic content, check out `docs/examples/smart_cache.py`.
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## Cache Mode Reference
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| Mode | Read from Cache | Write to Cache | Use Case |
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|------|----------------|----------------|----------|
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| `ENABLED` | ✓ | ✓ | Normal operation |
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| `DISABLED` | ✗ | ✗ | No caching needed |
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| `READ_ONLY` | ✓ | ✗ | Use existing cache only |
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| `WRITE_ONLY` | ✗ | ✓ | Refresh cache only |
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| `BYPASS` | ✗ | ✗ | Skip cache for this request |
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| `SMART` | ✓* | ✓ | Validate before using cache |
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*SMART mode reads from cache but validates it first with a HEAD request.
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@@ -37,6 +37,12 @@ This page provides a comprehensive list of example scripts that demonstrate vari
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| Storage State | Tutorial on managing browser storage state for persistence. | [View Guide](https://github.com/unclecode/crawl4ai/blob/main/docs/examples/storage_state_tutorial.md) |
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| Network Console Capture | Demonstrates how to capture and analyze network requests and console logs. | [View Code](https://github.com/unclecode/crawl4ai/blob/main/docs/examples/network_console_capture_example.py) |
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## Caching & Performance
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| Example | Description | Link |
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|---------|-------------|------|
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| SMART Cache Mode | Demonstrates the intelligent SMART cache mode that validates cached content using HEAD requests, saving 70-95% bandwidth while ensuring fresh content. | [View Code](https://github.com/unclecode/crawl4ai/blob/main/docs/examples/smart_cache.py) |
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## Extraction Strategies
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| Example | Description | Link |
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@@ -79,7 +79,7 @@ if __name__ == "__main__":
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asyncio.run(main())
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```
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> IMPORTANT: By default cache mode is set to `CacheMode.ENABLED`. So to have fresh content, you need to set it to `CacheMode.BYPASS`
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> IMPORTANT: By default cache mode is set to `CacheMode.ENABLED`. So to have fresh content, you need to set it to `CacheMode.BYPASS`. For intelligent caching that validates content before using cache, use the new `CacheMode.SMART` - it saves bandwidth while ensuring fresh content.
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We’ll explore more advanced config in later tutorials (like enabling proxies, PDF output, multi-tab sessions, etc.). For now, just note how you pass these objects to manage crawling.
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Reference in New Issue
Block a user