Previously robots.txt was fetched lazily on the first request per
domain, causing early concurrent requests to each stall waiting for
the same network fetch. The cache is now warmed before the crawl loop
starts, making all subsequent robots.txt lookups a local read.
- RobotsTxtManager gains a prefetch(urls, sid) method that fetches all domains concurrently via a task group
- CrawlerEngine._prefetch_robots_txt() is called after on_start():
uses allowed_domains if configured, otherwise falls back to unique
domains extracted from start_urls
- Mid-crawl domain discovery (not covered by prefetch) still fetches
lazily; two concurrent callbacks on the same new domain can each
trigger a fetch — accepted tradeoff, documented in _get_domain_delay
Files: scrapling/spiders/robotstxt.py, scrapling/spiders/engine.py, tests/spiders/test_engine.py
robots.txt is a domain-level document and does not vary by session.
Keying the cache by (domain, sid) was both wasteful and incorrect —
it caused redundant fetches when the same domain was accessed by different sessions.
- Cache is now keyed by domain string only; all sessions share one entry
- Removed asyncio.Event inflight-deduplication mechanism (superseded by the prefetch approach added in the next commit)
- clear_cache() loses the `sid` parameter (breaking change); clearing a domain now evicts the single shared entry for all sessions
- Updated tests to reflect shared-cache semantics
Files: scrapling/spiders/robotstxt.py, tests/spiders/test_robotstxt.py
SessionManager.fetch() pops `method` from `_session_kwargs`,
which mutates the original request dict. When the engine retries
a blocked request via request.copy(), the copy no longer has
`method`, so it defaults to GET.
Steps to reproduce:
1. Yield Request(url, method="POST", data=...)
2. Target returns a response that triggers is_blocked()
3. Engine retries via request.copy() → second fetch uses GET
Fix: copy the kwargs dict before popping, so the original
request stays intact.
Karim shoair