fix: Allowing InMemStore and FAISSDocStore for indexing using single worker (#3868)

* Allowing InMemStore and FAISSDocStore for indexing using single worker YAML config

* unified pipeline & doc store loading

* fix pylint warning

* separated tests

* removed unnecessay caplog

rest_api/rest_api/pipeline/__init__.py

@@ -13,9 +13,32 @@ from rest_api.controller.utils import RequestLimiter
 
 logger = logging.getLogger(__name__)
 
-# Since each instance of FAISSDocumentStore creates an in-memory FAISS index, the Indexing & Query Pipelines would
-# end up with different indices. The same applies for InMemoryDocumentStore.
-UNSUPPORTED_DOC_STORES = (FAISSDocumentStore, InMemoryDocumentStore)
+# Each instance of FAISSDocumentStore creates an in-memory FAISS index,
+# the Indexing & Query Pipelines will end up with different indices for each worker.
+# The same applies for InMemoryDocumentStore.
+SINGLE_PROCESS_DOC_STORES = (FAISSDocumentStore, InMemoryDocumentStore)
+
+
+def _load_pipeline(pipeline_yaml_path, indexing_pipeline_name):
+    # Load pipeline (if available)
+    try:
+        pipeline = Pipeline.load_from_yaml(Path(pipeline_yaml_path), pipeline_name=indexing_pipeline_name)
+        logging.info("Loaded pipeline nodes: %s", pipeline.graph.nodes.keys())
+        document_store = _get_pipeline_doc_store(pipeline)
+    except PipelineConfigError as e:
+        pipeline, document_store = None, None
+        logger.error(
+            "Error loading %s pipeline from %s. \n %s\n", indexing_pipeline_name, pipeline_yaml_path, e.message
+        )
+    return pipeline, document_store
+
+
+def _get_pipeline_doc_store(pipeline):
+    document_store = pipeline.get_document_store()
+    logging.info("Loaded docstore: %s", document_store)
+    if isinstance(document_store, SINGLE_PROCESS_DOC_STORES):
+        logger.warning("FAISSDocumentStore or InMemoryDocumentStore should only be used with 1 worker.")
+    return document_store
 
 
 def setup_pipelines() -> Dict[str, Any]:
@@ -24,14 +47,9 @@ def setup_pipelines() -> Dict[str, Any]:
 
     pipelines = {}
 
-    # Load query pipeline
-    query_pipeline = Pipeline.load_from_yaml(Path(config.PIPELINE_YAML_PATH), pipeline_name=config.QUERY_PIPELINE_NAME)
-    logging.info("Loaded pipeline nodes: %s", query_pipeline.graph.nodes.keys())
+    # Load query pipeline & document store
+    query_pipeline, document_store = _load_pipeline(config.PIPELINE_YAML_PATH, config.QUERY_PIPELINE_NAME)
     pipelines["query_pipeline"] = query_pipeline
-
-    # Find document store
-    document_store = query_pipeline.get_document_store()
-    logging.info("Loaded docstore: %s", document_store)
     pipelines["document_store"] = document_store
 
     # Setup concurrency limiter
@@ -39,24 +57,11 @@ def setup_pipelines() -> Dict[str, Any]:
     logging.info("Concurrent requests per worker: %s", config.CONCURRENT_REQUEST_PER_WORKER)
     pipelines["concurrency_limiter"] = concurrency_limiter
 
-    # Load indexing pipeline (if available)
-    try:
-        indexing_pipeline = Pipeline.load_from_yaml(
-            Path(config.PIPELINE_YAML_PATH), pipeline_name=config.INDEXING_PIPELINE_NAME
-        )
-        docstore = indexing_pipeline.get_document_store()
-        if isinstance(docstore, UNSUPPORTED_DOC_STORES):
-            indexing_pipeline = None
-            raise PipelineConfigError(
-                "Indexing pipelines with FAISSDocumentStore or InMemoryDocumentStore are not supported by the REST APIs."
-            )
-
-    except PipelineConfigError as e:
-        indexing_pipeline = None
-        logger.error("%s\nFile Upload API will not be available.", e.message)
-
-    finally:
-        pipelines["indexing_pipeline"] = indexing_pipeline
+    # Load indexing pipeline
+    index_pipeline, _ = _load_pipeline(config.PIPELINE_YAML_PATH, config.INDEXING_PIPELINE_NAME)
+    if not index_pipeline:
+        logger.warning("Indexing Pipeline is not setup. File Upload API will not be available.")
+    pipelines["indexing_pipeline"] = index_pipeline
 
     # Create directory for uploaded files
     os.makedirs(config.FILE_UPLOAD_PATH, exist_ok=True)

rest_api/test/samples/test.bogus_pipeline.yml

@@ -0,0 +1,17 @@
+version: 'ignore'
+
+components:
+  - name: InMemoryDocumentStore
+    params: {}
+    # Wrong DocumentStore Type
+    type: MyOwnDocumentStore
+  - name: tfidf_ret
+    params:
+      document_store: InMemoryDocumentStore
+    type: TfidfRetriever
+pipelines:
+  - name: query
+    nodes:
+      - inputs:
+          - Query
+        name: tfidf_ret

rest_api/test/samples/test.in-memory-haystack-pipeline.yml

@@ -0,0 +1,16 @@
+version: 'ignore'
+
+components:
+  - name: InMemoryDocumentStore
+    params: {}
+    type: InMemoryDocumentStore
+  - name: tfidf_ret
+    params:
+      document_store: InMemoryDocumentStore
+    type: TfidfRetriever
+pipelines:
+  - name: query
+    nodes:
+      - inputs:
+          - Query
+        name: tfidf_ret

rest_api/test/test_rest_api.py

@@ -5,25 +5,49 @@ from pathlib import Path
 from textwrap import dedent
 from unittest import mock
 from unittest.mock import MagicMock, Mock
-import functools
 import numpy as np
 import pandas as pd
 
 import pytest
 from fastapi.testclient import TestClient
-from haystack import Document, Answer
+from haystack import Document, Answer, Pipeline
 import haystack
 from haystack.nodes import BaseReader, BaseRetriever
 from haystack.document_stores import BaseDocumentStore
+from haystack.errors import PipelineSchemaError
 from haystack.schema import Label, FilterType
 from haystack.nodes.file_converter import BaseConverter
 
+from rest_api.pipeline import _load_pipeline
 from rest_api.utils import get_app
 
 
 TEST_QUERY = "Who made the PDF specification?"
 
 
+def test_single_worker_warning_for_indexing_pipelines(caplog):
+    yaml_pipeline_path = Path(__file__).parent.resolve() / "samples" / "test.in-memory-haystack-pipeline.yml"
+    p, _ = _load_pipeline(yaml_pipeline_path, None)
+
+    assert isinstance(p, Pipeline)
+    assert "used with 1 worker" in caplog.text
+
+
+def test_check_error_for_pipeline_not_found():
+
+    yaml_pipeline_path = Path(__file__).parent.resolve() / "samples" / "test.in-memory-haystack-pipeline.yml"
+    p, _ = _load_pipeline(yaml_pipeline_path, "ThisPipelineDoesntExist")
+    assert p is None
+
+
+def test_bad_yaml_pipeline_configuration_error():
+
+    yaml_pipeline_path = Path(__file__).parent.resolve() / "samples" / "test.bogus_pipeline.yml"
+    with pytest.raises(PipelineSchemaError) as excinfo:
+        _load_pipeline(yaml_pipeline_path, None)
+    assert "MyOwnDocumentStore" in str(excinfo.value)
+
+
 class MockReader(BaseReader):
     outgoing_edges = 1