feat: Use langchain parent document retriever to simplify retrieval logic

.gitignore

@@ -14,4 +14,6 @@ mlruns/
 mlartifacts/
 
 # Weaviate vector store
-weaviate/
+weaviate/
+
+data/

indexing.py

@@ -1,3 +1,4 @@
+import asyncio
 import logging
 import os
 from typing import Iterable, TypedDict
@@ -5,6 +6,7 @@ from typing import Iterable, TypedDict
 import langchain
 import langchain.chat_models
 import langchain.prompts
+import langchain.retrievers
 import langchain.text_splitter
 import langchain_core
 import langchain_core.documents
@@ -16,11 +18,12 @@ import slack
 import weaviate
 from hn import HackerNewsClient, Story
 from scrape import JinaScraper
+from util import DocumentLocalFileStore
 
-NUM_STORIES = 20
-USER_PREFERENCES = ["Machine Learning", "Programming", "Robotics"]
+NUM_STORIES = 40  # Number of top stories to fetch from Hacker News
+USER_PREFERENCES = ["Machine Learning", "Programming", "DevOps"]
 ENABLE_SLACK = True  # Send updates to Slack, need to set SLACK_BOT_TOKEN env var
-ENABLE_MLFLOW_TRACING = False  # Use MLflow (at http://localhost:5000) for tracing
+ENABLE_MLFLOW_TRACING = True  # Use MLflow (at http://localhost:5000) for tracing
 
 
 llm = langchain.chat_models.init_chat_model(
@@ -36,6 +39,18 @@ vector_store = langchain_weaviate.WeaviateVectorStore(
     embedding=embeddings,
 )
 
+splitter = langchain.text_splitter.RecursiveCharacterTextSplitter(
+    chunk_size=2000,
+    chunk_overlap=200,
+)
+
+doc_store = DocumentLocalFileStore(root_path="data/documents")
+retriever = langchain.retrievers.ParentDocumentRetriever(
+    vectorstore=vector_store,
+    docstore=doc_store,
+    child_splitter=splitter,
+)
+
 
 class State(TypedDict):
     preferences: Iterable[str]
@@ -44,70 +59,15 @@ class State(TypedDict):
     summaries: list[dict]
 
 
-def retrieve(state: State, top_n: int = 2 * len(USER_PREFERENCES)) -> State:
-    # Search for relevant documents (with scores if available)
-    retrieved_docs = vector_store.similarity_search(
-        "Show the most interesting articles about the following topics: "
-        + ", ".join(state["preferences"]),
-        k=top_n * 20,  # Chunks, not complete stories
-        return_score=True
-        if hasattr(vector_store, "similarity_search_with_score")
-        else False,
-    )
+def retrieve_docs(state: State, top_n: int = 3):
+    """Retrieve relevant documents based on user preferences."""
 
-    # If scores are returned, unpack (doc, score) tuples; else, set score to None
-    docs_with_scores = []
-    if retrieved_docs and isinstance(retrieved_docs[0], tuple):
-        for doc, score in retrieved_docs:
-            docs_with_scores.append((doc, score))
-    else:
-        for doc in retrieved_docs:
-            docs_with_scores.append((doc, None))
+    docs = []
+    for preference in state["preferences"]:
+        logging.info(f"Retrieving documents for preference: {preference}")
+        docs.extend(retriever.invoke(preference)[:top_n])
 
-    # Group chunks by story_id and collect their scores
-    story_groups = {}
-    for doc, score in docs_with_scores:
-        story_id = doc.metadata.get("story_id")
-        if story_id not in story_groups:
-            story_groups[story_id] = []
-        story_groups[story_id].append((doc, score))
-
-    # Aggregate max score per story and reconstruct complete stories
-    story_scores = {}
-    complete_stories = []
-    for story_id, chunks_scores in story_groups.items():
-        chunks = [doc for doc, _ in chunks_scores]
-        scores = [s for _, s in chunks_scores if s is not None]
-        max_score = max(scores) if scores else None
-        story_scores[story_id] = max_score
-        if len(chunks) == 1:
-            complete_stories.append((chunks[0], max_score))
-        else:
-            combined_content = "\n\n".join(
-                chunk.page_content
-                for chunk in sorted(
-                    chunks, key=lambda x: x.metadata.get("chunk_index", 0)
-                )
-            )
-            complete_story = langchain_core.documents.Document(
-                page_content=combined_content,
-                metadata=chunks[0].metadata,  # Use metadata from first chunk
-            )
-            complete_stories.append((complete_story, max_score))
-
-    # Sort stories by max_score descending (None scores go last)
-    complete_stories_sorted = sorted(
-        complete_stories, key=lambda x: (x[1] is not None, x[1]), reverse=True
-    )
-
-    # Return top_n stories
-    top_stories = [doc for doc, _ in complete_stories_sorted[:top_n]]
-    return {
-        "preferences": state["preferences"],
-        "context": top_stories,
-        "answer": state.get("answer", ""),
-        "summaries": state.get("summaries", []),
-    }
+    return {"context": docs}
 
 
 def generate_structured_summaries(state: State):
@@ -217,9 +177,9 @@ def run_structured_query(
 ) -> list[dict]:
     """Run query and return structured summary data."""
     graph_builder = langgraph.graph.StateGraph(State).add_sequence(
-        [retrieve, generate_structured_summaries]
+        [retrieve_docs, generate_structured_summaries]
     )
-    graph_builder.add_edge(langgraph.graph.START, "retrieve")
+    graph_builder.add_edge(langgraph.graph.START, "retrieve_docs")
     graph = graph_builder.compile()
 
     response = graph.invoke(
@@ -246,6 +206,7 @@ def get_existing_story_ids() -> set[str]:
 
 async def fetch_hn_top_stories(
     limit: int = 10,
+    force_fetch: bool = False,
 ) -> list[langchain_core.documents.Document]:
     hn = HackerNewsClient()
     stories = await hn.get_top_stories(limit=limit)
@@ -256,11 +217,15 @@ async def fetch_hn_top_stories(
 
     new_stories = [story for story in stories if story.id not in existing_ids]
 
-    print(f"Found {len(stories)} top stories, {len(new_stories)} are new")
+    logging.info(f"Found {len(stories)} top stories, {len(new_stories)} are new")
 
     if not new_stories:
-        print("No new stories to fetch")
-        return []
+        if not force_fetch:
+            logging.info("No new stories to fetch")
+            return []
+        else:
+            logging.info("Force fetching all top stories regardless of existing IDs")
+            new_stories = stories
 
     contents = {}
 
@@ -268,26 +233,18 @@ async def fetch_hn_top_stories(
     scraper = JinaScraper(os.getenv("JINA_API_KEY"))
 
     async def _fetch_content(story: Story) -> tuple[str, str]:
-        try:
-            if not story.url:
-                return story.id, story.title
-            return story.id, await scraper.get_content(story.url)
-        except Exception as e:
-            logging.warning(f"Failed to fetch content for story {story.id}: {e}")
-            return story.id, story.title  # Fallback to title if content fetch fails
+        if not story.url:
+            return story.id, story.title
+        return story.id, await scraper.get_content(story.url)
 
     tasks = [_fetch_content(story) for story in new_stories]
-    results = await asyncio.gather(*tasks, return_exceptions=True)
+    results = await asyncio.gather(*tasks)
 
     # Filter out exceptions and convert to dict
     contents = {}
     for result in results:
-        if isinstance(result, Exception):
-            logging.error(f"Task failed with exception: {result}")
-            continue
-        if isinstance(result, tuple) and len(result) == 2:
-            story_id, content = result
-            contents[story_id] = content
+        story_id, content = result
+        contents[story_id] = content
 
     documents = [
         langchain_core.documents.Document(
@@ -324,31 +281,15 @@ async def main():
         for story in new_stories:
             categories = categorize(story, llm)
             story.metadata["categories"] = list(categories)
-            print(f"Story ID {story.metadata["story_id"]} categorized as: {categories}")
+            print(
+                f"Story ID {story.metadata["story_id"]} ({story.metadata["title"]}) categorized as: {categories}"
+            )
 
-        # 2. Split
-        documents_to_store = []
-        for story in new_stories:
-            # If article is short enough, store as-is
-            if len(story.page_content) <= 3000:
-                documents_to_store.append(story)
-            else:
-                # For very long articles, chunk but keep story metadata
-                splitter = langchain.text_splitter.RecursiveCharacterTextSplitter(
-                    chunk_size=2000,
-                    chunk_overlap=200,
-                    add_start_index=True,
-                )
-                chunks = splitter.split_documents([story])
-                # Add chunk info to metadata
-                for i, chunk in enumerate(chunks):
-                    chunk.metadata["chunk_index"] = i
-                    chunk.metadata["total_chunks"] = len(chunks)
-                documents_to_store.extend(chunks)
-
-        # 3. Store
-        _ = vector_store.add_documents(documents_to_store)
-        print(f"Added {len(documents_to_store)} documents to vector store")
+        # 2. Split & 3. Store
+        retriever.add_documents(
+            new_stories, ids=[doc.metadata["story_id"] for doc in new_stories]
+        )
+        print(f"Added {len(new_stories)} documents to document store")
     else:
         print("No new stories to process")
 
@@ -361,8 +302,6 @@ async def main():
 
 
 if __name__ == "__main__":
-    import asyncio
-
     logging.basicConfig(level=logging.INFO)
 
     try:

scrape.py

@@ -1,4 +1,3 @@
-import asyncio
 import logging
 from abc import ABC, abstractmethod
 from typing import override
@@ -8,41 +7,22 @@ import httpx
 
 class TextScraper(ABC):
     def __init__(self):
-        self._client = httpx.AsyncClient(timeout=httpx.Timeout(5.0))
+        self._http_headers = {}
 
     async def _fetch_text(self, url: str) -> str:
         """Fetch the raw HTML content from the URL."""
-        response = None
         try:
-            response = await self._client.get(url)
-            response.raise_for_status()
-            return response.text
+            async with httpx.AsyncClient(headers=self._http_headers) as client:
+                response = await client.get(url)
+                response.raise_for_status()
+                return response.text
         except Exception:
             logging.warning(f"Failed to fetch text from {url}", exc_info=True)
             raise
-        finally:
-            if response:
-                await response.aclose()
 
     @abstractmethod
     async def get_content(self, url: str) -> str: ...
 
-    async def close(self):
-        """Close the underlying HTTP client."""
-        if self._client and not self._client.is_closed:
-            await self._client.aclose()
-
-    def __del__(self):
-        """Ensure the HTTP client is closed when the object is deleted."""
-        try:
-            loop = asyncio.get_event_loop()
-            if loop.is_running():
-                loop.create_task(self.close())
-            else:
-                loop.run_until_complete(self.close())
-        except Exception:
-            pass
-
 
 class Html2textScraper(TextScraper):
     @override
@@ -65,7 +45,7 @@ class JinaScraper(TextScraper):
     def __init__(self, api_key: str | None = None):
         super().__init__()
         if api_key:
-            self._client.headers.update({"Authorization": f"Bearer {api_key}"})
+            self._http_headers.update({"Authorization": f"Bearer {api_key}"})
 
     @override
     async def get_content(self, url: str) -> str:

slack.py

@@ -77,6 +77,7 @@ def send_message(channel: str, blocks: list) -> None:
             text="Tech updates",
             blocks=blocks,
             unfurl_links=False,
+            unfurl_media=False,
         )
         response.validate()
         logging.info(f"Message sent successfully to channel {channel}")

util.py

@@ -0,0 +1,48 @@
+import json
+from collections.abc import Iterator
+
+from langchain.schema import BaseStore, Document
+from langchain.storage import LocalFileStore
+
+
+class DocumentLocalFileStore(BaseStore[str, Document]):
+    def __init__(self, root_path: str):
+        self.store = LocalFileStore(root_path)
+
+    def mget(self, keys):
+        """Get multiple documents by keys"""
+        results = []
+        for key in keys:
+            try:
+                serialized = self.store.mget([key])[0]
+                if serialized:
+                    # Deserialize the document
+                    doc_dict = json.loads(serialized.decode("utf-8"))
+                    doc = Document(
+                        page_content=doc_dict["page_content"],
+                        metadata=doc_dict.get("metadata", {}),
+                    )
+                    results.append(doc)
+                else:
+                    results.append(None)
+            except:
+                results.append(None)
+        return results
+
+    def mset(self, key_value_pairs):
+        """Set multiple key-value pairs"""
+        serialized_pairs = []
+        for key, doc in key_value_pairs:
+            # Serialize the document
+            doc_dict = {"page_content": doc.page_content, "metadata": doc.metadata}
+            serialized = json.dumps(doc_dict).encode("utf-8")
+            serialized_pairs.append((key, serialized))
+
+        self.store.mset(serialized_pairs)
+
+    def mdelete(self, keys):
+        """Delete multiple keys"""
+        self.store.mdelete(keys)
+
+    def yield_keys(self, *, prefix: str | None = None) -> Iterator[str]:
+        return self.store.yield_keys(prefix=prefix)