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fix: wrap blocking readability call with asyncio.to_thread in web_fetch (#2157) 

* fix: wrap blocking readability call with asyncio.to_thread in web_fetch

The readability extractor internally spawns a Node.js subprocess via
readabilipy, which blocks the async event loop and causes a
BlockingError when web_fetch is invoked inside LangGraph's async
runtime.

Wrap the synchronous extract_article call with asyncio.to_thread to
offload it to a thread pool, unblocking the event loop.

Note: community/infoquest/tools.py has the same latent issue and
should be addressed in a follow-up PR.

Closes #2152

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: verify web_fetch offloads extraction via asyncio.to_thread

Add a regression test that monkeypatches asyncio.to_thread to confirm
readability extraction is offloaded to a worker thread, preventing
future refactors from reintroducing the blocking call.

Addresses Copilot review feedback on #2157.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
This commit is contained in:
lesliewangwyc-dev 2026-04-13 21:15:24 +08:00 committed by GitHub
parent 5db71cb68c
commit 1df389b9d0
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2 changed files with 30 additions and 1 deletions
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4
backend/packages/harness/deerflow/community/jina_ai/tools.py
View File

@ -1,3 +1,5 @@
import asyncio
from langchain.tools import tool from langchain.tools import tool
from deerflow.community.jina_ai.jina_client import JinaClient from deerflow.community.jina_ai.jina_client import JinaClient
@ -26,5 +28,5 @@ async def web_fetch_tool(url: str) -> str:
html_content = await jina_client.crawl(url, return_format="html", timeout=timeout) html_content = await jina_client.crawl(url, return_format="html", timeout=timeout)
if isinstance(html_content, str) and html_content.startswith("Error:"): if isinstance(html_content, str) and html_content.startswith("Error:"):
return html_content return html_content
article = readability_extractor.extract_article(html_content) article = await asyncio.to_thread(readability_extractor.extract_article, html_content)
return article.to_markdown()[:4096] return article.to_markdown()[:4096]

27
backend/tests/test_jina_client.py
View File

@ -175,3 +175,30 @@ async def test_web_fetch_tool_returns_markdown_on_success(monkeypatch):
result = await web_fetch_tool.ainvoke("https://example.com") result = await web_fetch_tool.ainvoke("https://example.com")
assert "Hello world" in result assert "Hello world" in result
assert not result.startswith("Error:") assert not result.startswith("Error:")
@pytest.mark.anyio
async def test_web_fetch_tool_offloads_extraction_to_thread(monkeypatch):
"""Test that readability extraction is offloaded via asyncio.to_thread to avoid blocking the event loop."""
import asyncio
async def mock_crawl(self, url, **kwargs):
return "<html><body><p>threaded</p></body></html>"
mock_config = MagicMock()
mock_config.get_tool_config.return_value = None
monkeypatch.setattr("deerflow.community.jina_ai.tools.get_app_config", lambda: mock_config)
monkeypatch.setattr(JinaClient, "crawl", mock_crawl)
to_thread_called = False
original_to_thread = asyncio.to_thread
async def tracking_to_thread(func, *args, **kwargs):
nonlocal to_thread_called
to_thread_called = True
return await original_to_thread(func, *args, **kwargs)
monkeypatch.setattr("deerflow.community.jina_ai.tools.asyncio.to_thread", tracking_to_thread)
result = await web_fetch_tool.ainvoke("https://example.com")
assert to_thread_called, "extract_article must be called via asyncio.to_thread to avoid blocking the event loop"
assert "threaded" in result