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Long-Term Efficiency

Ensuring the scraping system operates efficiently over the long term involves optimizing resource usage, minimizing redundant work, and reducing costs.

Caching Strategies

  • Purpose: Avoid re-fetching or re-processing data that hasn't changed.
  • HTTP Caching (Conditional):
    • Respect standard HTTP caching headers (ETag, Last-Modified) sent by target websites if appropriate. The requests library can sometimes handle this partially.
    • Caution: Aggressive client-side HTTP caching can sometimes interfere with detecting fresh content on job boards. Needs careful implementation if used.
  • Application-Level Caching:
    • Raw HTML Cache: Before initiating a parse task, check if the raw HTML for a specific URL/version already exists in S3 (or a faster cache like Redis if needed, though S3 is often sufficient).
    • Parsed Data Cache (Less Common): If parsing is extremely expensive and source HTML changes infrequently, potentially cache the structured output, but this adds complexity in cache invalidation.
    • Configuration Cache: Cache frequently accessed configuration details in the dispatcher or workers to reduce load on the config database.

Incremental Scraping

  • Goal: Avoid repeatedly scraping job listings that have already been processed and haven't changed. Focus on new or updated listings.
  • Strategies:
    • Date Filters: Leverage website features to filter searches by "posted in last 24 hours" or "posted since [date]". This is the most direct approach if available and reliable. Store the filter logic in the configuration database.
    • Identify New Listings: When scraping search result pages, compare the found Job IDs or URLs against those recently seen/stored in the structured database. Only yield requests for new/unseen detail pages.
    • Detect Updates (Harder): For already scraped jobs, periodically re-scrape detail pages and compare key fields or a hash of the content to detect significant updates. This is more resource-intensive. A last_checked_timestamp in the structured data can help manage this.

API Alternatives

  • Reiteration: Before building a scraper for a website, always investigate if a public or private API exists that provides the required job data.
  • Benefits: APIs are generally more stable, efficient, provide structured data (often JSON), and are the intended way to access data programmatically.
  • Process: Use browser developer tools to monitor network requests while interacting with the target site. Look for XHR/Fetch requests that return structured data.

Resource Optimization

  • Tool Selection: Prefer lightweight tools (requests) over heavyweight ones (Playwright) whenever possible. Use Playwright only when strictly necessary for JS rendering or complex interactions.
  • Efficient Parsing: Use efficient HTML parsing libraries like lxml.
  • Concurrency Tuning: Adjust the number of concurrent workers (Celery) and potentially internal concurrency settings (e.g., Playwright browser contexts) based on monitoring data (CPU/RAM usage, task duration, external site responsiveness) to maximize throughput without overloading resources or getting banned.
  • Instance Sizing: Choose appropriate instance sizes (CPU/RAM) for worker nodes, database instances, and other services based on observed load. Use cloud provider auto-scaling features where applicable (especially K8s HPA).
  • Data Compression: Compress raw HTML stored in S3 using gzip or brotli to reduce storage costs.

Parallel Processing

  • Mechanism: Primarily achieved through running multiple Celery workers concurrently, potentially distributed across multiple machines managed by Kubernetes.
  • Benefits: Enables high throughput by processing many scraping and parsing tasks simultaneously.
  • Considerations: Ensure downstream resources (databases, APIs) can handle the concurrent load. Manage shared resources like proxy pools effectively across workers.

By focusing on these efficiency measures, the system can minimize redundant work, optimize resource consumption, and operate more cost-effectively at scale.