使用Scrapy搭建搜索引擎：爬虫速度提升空间及合理速率咨询

Hey there! Let's dive into your Scrapy crawling speed questions—first off, hitting ~9300 pages/hour is already a solid start! Let's break down the room for improvement and industry benchmarks below.

There are several levers you can pull to boost your crawl speed, depending on your target site's constraints and your current setup:

• Tweak Scrapy core configurations: Start with adjusting CONCURRENT_REQUESTS (default 16) and CONCURRENT_REQUESTS_PER_DOMAIN. If the target site has robust servers and no strict anti-scraping rules, you can bump CONCURRENT_REQUESTS to 30-50 (test incrementally to avoid triggering blocks). Also, lower DOWNLOAD_DELAY if you're not hitting rate limits—just don't set it to 0 unless you're sure the site allows it. Enabling DNSCACHE_ENABLED can also cut down on DNS lookup overhead.
• Optimize data processing pipelines: If your item parsing or storage is bottlenecking the crawl, shift those heavy operations to async threads or batch processing. For example, use bulk inserts for databases instead of writing one item at a time, and avoid overly complex regex in your selectors—stick to Scrapy's built-in xpath/css methods which are optimized.
• Leverage distributed crawling: Once a single machine hits its CPU/network limit, use Scrapy-Redis to spin up a cluster of crawlers. This lets you split the workload across multiple servers, which can multiply your crawl rate exponentially for large-scale projects.
• Refine anti-scraping bypasses: If you're facing retries or IP blocks, implementing a rotating proxy pool and user-agent pool will help maintain consistent speed. You can also adjust request timing to mimic human behavior (e.g., randomize delays slightly) to avoid triggering rate limits.

What counts as "good" depends heavily on the target site's size, anti-scraping defenses, and your project's goals:

• Small-to-medium static sites (no strict anti-scraping): A rate of 10,000–20,000 pages/hour is considered strong, with well-optimized crawlers hitting even higher.
• Large sites with anti-scraping (e.g., e-commerce, news portals): Stabilizing at 2,000–8,000 pages/hour is solid—these sites often have strict rate limits, so balancing speed with avoiding blocks is key. For heavily guarded platforms like Amazon or social media sites, even 500–2,000 pages/hour can be a "good" rate if it's consistent.
• Search engine-scale crawling: Major engines like Google or Baidu crawl millions of pages per hour, but this relies on massive distributed clusters, direct partnerships with sites, and sophisticated crawling logic that's way beyond most small-scale projects.

Your current 9300 pages/hour is already above average for many scenarios—if you're crawling a site with mild anti-scraping, you might have a bit more room to grow; if it's a strict site, you're probably already in a good spot.

内容的提问来源于stack exchange，提问作者Nilesh Guria