IMPROVEMENT WebResearchRetriever error handling in urls with connection error (#13401)

- **Description:** Added a method `fetch_valid_documents` to
`WebResearchRetriever` class that will test the connection for every url
in `new_urls` and remove those that raise a `ConnectionError`.
- **Issue:** [Previous
PR](https://github.com/langchain-ai/langchain/pull/13353),
  - **Dependencies:** None,
  - **Tag maintainer:** @efriis 

Please make sure your PR is passing linting and testing before
submitting. Run `make format`, `make lint` and `make test` to check this
locally.

See contribution guidelines for more information on how to write/run
tests, lint, etc:

https://github.com/langchain-ai/langchain/blob/master/.github/CONTRIBUTING.md

If you're adding a new integration, please include:
1. a test for the integration, preferably unit tests that do not rely on
network access,
2. an example notebook showing its use. It lives in `docs/extras`
directory.

If no one reviews your PR within a few days, please @-mention one of
@baskaryan, @eyurtsev, @hwchase17.

libs/langchain/langchain/document_loaders/async_html.py

@@ -51,6 +51,7 @@ class AsyncHtmlLoader(BaseLoader):
         requests_per_second: int = 2,
         requests_kwargs: Optional[Dict[str, Any]] = None,
         raise_for_status: bool = False,
+        ignore_load_errors: bool = False,
     ):
         """Initialize with a webpage path."""
 
@@ -88,6 +89,17 @@ class AsyncHtmlLoader(BaseLoader):
         self.raise_for_status = raise_for_status
         self.autoset_encoding = autoset_encoding
         self.encoding = encoding
+        self.ignore_load_errors = ignore_load_errors
+
+    def _fetch_valid_connection_docs(self, url: str) -> Any:
+        if self.ignore_load_errors:
+            try:
+                return self.session.get(url, **self.requests_kwargs)
+            except Exception as e:
+                warnings.warn(str(e))
+                return None
+
+        return self.session.get(url, **self.requests_kwargs)
 
     @staticmethod
     def _check_parser(parser: str) -> None:
@@ -114,7 +126,10 @@ class AsyncHtmlLoader(BaseLoader):
 
         self._check_parser(parser)
 
-        html_doc = self.session.get(url, **self.requests_kwargs)
+        html_doc = self._fetch_valid_connection_docs(url)
+        if not getattr(html_doc, "ok", False):
+            return None
+
         if self.raise_for_status:
             html_doc.raise_for_status()
 
@@ -142,7 +157,10 @@ class AsyncHtmlLoader(BaseLoader):
                             text = ""
                         return text
                 except aiohttp.ClientConnectionError as e:
-                    if i == retries - 1:
+                    if i == retries - 1 and self.ignore_load_errors:
+                        logger.warning(f"Error fetching {url} after {retries} retries.")
+                        return ""
+                    elif i == retries - 1:
                         raise
                     else:
                         logger.warning(
@@ -196,6 +214,8 @@ class AsyncHtmlLoader(BaseLoader):
         docs = []
         for i, text in enumerate(cast(List[str], results)):
             soup = self._scrape(self.web_paths[i])
+            if not soup:
+                continue
             metadata = _build_metadata(soup, self.web_paths[i])
             docs.append(Document(page_content=text, metadata=metadata))
 

libs/langchain/langchain/retrievers/web_research.py

@@ -198,7 +198,7 @@ class WebResearchRetriever(BaseRetriever):
         logger.info(f"New URLs to load: {new_urls}")
         # Load, split, and add new urls to vectorstore
         if new_urls:
-            loader = AsyncHtmlLoader(new_urls)
+            loader = AsyncHtmlLoader(new_urls, ignore_load_errors=True)
             html2text = Html2TextTransformer()
             logger.info("Indexing new urls...")
             docs = loader.load()