deepset-ai/haystack · error · TypeError

Document store {type(self.document_store).__name__} does not

Error message

Document store {type(self.document_store).__name__} does not provide async support.

What it means

DocumentWriter.run_async requires the configured document store to implement write_documents_async. If the store object lacks that attribute, a TypeError is raised because the async write cannot be performed. The sync run() works with the same store; only the async path is affected.

Source

Thrown at haystack/components/writers/document_writer.py:124

        but can be used with `await` in async code.

        :param documents:
            A list of documents to write to the document store.
        :param policy:
            The policy to use when encountering duplicate documents.
        :returns:
            Number of documents written to the document store.

        :raises ValueError:
            If the specified document store is not found.
        :raises TypeError:
            If the specified document store does not implement `write_documents_async`.
        """
        if policy is None:
            policy = self.policy

        if not hasattr(self.document_store, "write_documents_async"):
            raise TypeError(f"Document store {type(self.document_store).__name__} does not provide async support.")

        documents_written = await self.document_store.write_documents_async(documents=documents, policy=policy)
        return {"documents_written": documents_written}

    def close(self) -> None:
        """
        Release the synchronous resources of the underlying Document Store.
        """
        if hasattr(self.document_store, "close"):
            self.document_store.close()

    async def close_async(self) -> None:
        """
        Release the asynchronous resources of the underlying Document Store.
        """
        if hasattr(self.document_store, "close_async"):
            await self.document_store.close_async()

View on GitHub (pinned to e318778c9b)

Solutions

1. Use an async-capable document store (e.g. a store that implements write_documents_async) instead of InMemoryDocumentStore.
2. Fall back to the synchronous DocumentWriter.run() in async code via asyncio.to_thread(run, ...) if the store has no async support.
3. If it's a custom store, implement write_documents_async (often trivially wrapping write_documents or an async client call).
4. Upgrade the document store integration package to a version that adds async write support.

Example fix

// before
writer = DocumentWriter(document_store=InMemoryDocumentStore())
await writer.run_async(documents=docs)
// after
writer = DocumentWriter(document_store=QdrantDocumentStore(url=...))  # supports write_documents_async
await writer.run_async(documents=docs)

if not hasattr(writer.document_store, "write_documents_async"):
    result = await asyncio.to_thread(writer.run, documents=docs, policy=policy)
else:
    result = await writer.run_async(documents=docs, policy=policy)

def supports_async_write(store) -> TypeGuard[WriteDocumentsAsyncDocumentStore]:
    return hasattr(store, "write_documents_async") and callable(store.write_documents_async)

try:
    result = await writer.run_async(documents=docs)
except TypeError as e:
    if "does not provide async support" in str(e):
        result = await asyncio.to_thread(writer.run, documents=docs)

When it happens

Trigger: Awaiting DocumentWriter.run_async (or running an async pipeline containing it) when self.document_store is an InMemoryDocumentStore or any custom/legacy store that doesn't define write_documents_async.

Common situations: Using InMemoryDocumentStore (no async support) in an async pipeline; custom DocumentStore implementations that only ported the sync API; older third-party store integrations predating the async API.

Related errors

• Document store {type(self.document_store).__name__} does not
• Parameters of 'run' and 'run_async' methods must be the same
• Method 'run_async' of component '{cls.__name__}' must be a c
• The following tool names are not valid: {invalid_tool_names}
• user_prompt must define exactly one message block, found {le

AI-assisted analysis of deepset-ai/haystack@e318778c9b (2026-08-30). Data as JSON: /api/errors/bcc12b6f2d02bfdb. Report an issue: GitHub.