perf(memory-storage): avoid O(n) deque scan on forefront re-add#2074
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anxkhn wants to merge 2 commits into
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perf(memory-storage): avoid O(n) deque scan on forefront re-add#2074anxkhn wants to merge 2 commits into
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Pull request overview
This PR optimizes the in-memory RequestQueue client by eliminating the O(n) deque.remove scan when re-adding already-pending requests with forefront=True, replacing it with an appendleft + “lazy stale entry” skipping approach in fetch_next_request() / is_empty().
Changes:
- Reworked
MemoryRequestQueueClient.add_batch_of_requests()so forefront re-adds of pending requests no longer scan/remove from the pendingdeque. - Added stale-entry skipping in
fetch_next_request()and front-pruning inis_empty()to support the new “tombstone” behavior. - Added regression tests to guard the performance fix and ordering/dedup semantics.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
src/crawlee/storage_clients/_memory/_request_queue_client.py |
Implements tombstone-based forefront repositioning and stale-entry skipping/pruning logic. |
tests/unit/storage_clients/_memory/test_memory_rq_client.py |
Adds regression tests validating no deque.remove usage and preserves order/dedup semantics. |
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vdusek
requested changes
Jul 15, 2026
`MemoryRequestQueueClient.add_batch_of_requests` repositioned an already-pending request to the forefront with `deque.remove`, a linear scan of the whole pending deque. Re-adding a batch of K already-pending requests to a deque of N was O(K*N). Forefront re-adds are a real path: tiered-proxy retries set `request.forefront = True` and re-enqueue while the request is still pending. The forefront reposition now just `appendleft`s the request and leaves the old entry in place. The new object is registered in `_requests_by_unique_key`, superseding the old one, and `fetch_next_request` and `is_empty` skip entries whose object is no longer the one registered for their unique key. Because a forefront reposition always enqueues the live copy ahead of the entry it supersedes, `is_empty` can safely prune stale entries from the front. Only forefront re-adds create such tombstones. A regular re-add of an already-pending request leaves both the deque entry and its registered object untouched, so the identity check never misfires and no request is dropped. Forefront-LIFO / regular-FIFO order and deduplication are unchanged. Signed-off-by: Anas Khan <83116240+anxkhn@users.noreply.github.com>
Replace lazy deque tombstones with an ordered mapping so forefront repositioning remains constant-time without stale-entry growth. Keep request updates on regular re-adds, update reclaimed request instances in the index, and leave is_empty side-effect free. Signed-off-by: Anas Khan <83116240+anxkhn@users.noreply.github.com>
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MemoryRequestQueueClient.add_batch_of_requestsrepositioned an already-pending request withdeque.remove, making each forefront re-add O(n) and a batch of re-adds O(n²).This change replaces the pending deque with an
OrderedDictkeyed by request unique key. Forefront re-adds now reposition requests in constant time without creating stale entries, while regular re-adds preserve position and update the stored request object. Reclaimed request updates are also reflected in the lookup index, andis_emptyremains side-effect free.Forefront LIFO ordering, regular FIFO ordering, deduplication, and metadata counts are preserved.
This is the memory-client counterpart to #2011.
Issues
Testing
uv run ruff format --check src/crawlee/storage_clients/_memory/_request_queue_client.py tests/unit/storage_clients/_memory/test_memory_rq_client.pyuv run ruff check src/crawlee/storage_clients/_memory/_request_queue_client.py tests/unit/storage_clients/_memory/test_memory_rq_client.pyuv run poe type-checkuv run pytest tests/unit/storage_clients/_memory/test_memory_rq_client.py tests/unit/storages/test_request_queue.py tests/unit/storages/test_request_manager_tandem.py(300 passed, 2 skipped)Checklist