feat: defer the database connection to when it's needed (#769)

* feat: defer the database connection to when it's needed

* fix typing

* test init is lazy

integrations/astra/src/haystack_integrations/document_stores/astra/document_store.py

@@ -85,6 +85,7 @@ def __init__(
                 "Set the ASTRA_DB_API_ENDPOINT environment variable (recommended) or pass it explicitly."
             )
             raise ValueError(msg)
+        self.resolved_api_endpoint = resolved_api_endpoint
 
         resolved_token = token.resolve_value()
         if resolved_token is None:
@@ -93,6 +94,7 @@ def __init__(
                 "Set the ASTRA_DB_APPLICATION_TOKEN environment variable (recommended) or pass it explicitly."
             )
             raise ValueError(msg)
+        self.resolved_token = resolved_token
 
         self.api_endpoint = api_endpoint
         self.token = token
@@ -101,15 +103,20 @@ def __init__(
         self.duplicates_policy = duplicates_policy
         self.similarity = similarity
         self.namespace = namespace
-
-        self.index = AstraClient(
-            resolved_api_endpoint,
-            resolved_token,
-            self.collection_name,
-            self.embedding_dimension,
-            self.similarity,
-            namespace,
-        )
+        self._index: Optional[AstraClient] = None
+
+    @property
+    def index(self) -> AstraClient:
+        if self._index is None:
+            self._index = AstraClient(
+                self.resolved_api_endpoint,
+                self.resolved_token,
+                self.collection_name,
+                self.embedding_dimension,
+                self.similarity,
+                self.namespace,
+            )
+        return self._index
 
     @classmethod
     def from_dict(cls, data: Dict[str, Any]) -> "AstraDocumentStore":

integrations/astra/tests/test_document_store.py

@@ -20,13 +20,19 @@ def mock_auth(monkeypatch):
     monkeypatch.setenv("ASTRA_DB_APPLICATION_TOKEN", "test_token")
 
 
+@mock.patch("haystack_integrations.document_stores.astra.astra_client.AstraDB")
+def test_init_is_lazy(_mock_client):
+    _ = AstraDocumentStore()
+    _mock_client.assert_not_called()
+
+
 def test_namespace_init(mock_auth):  # noqa
     with mock.patch("haystack_integrations.document_stores.astra.astra_client.AstraDB") as client:
-        AstraDocumentStore()
+        _ = AstraDocumentStore().index
         assert "namespace" in client.call_args.kwargs
         assert client.call_args.kwargs["namespace"] is None
 
-        AstraDocumentStore(namespace="foo")
+        _ = AstraDocumentStore(namespace="foo").index
         assert "namespace" in client.call_args.kwargs
         assert client.call_args.kwargs["namespace"] == "foo"