feat: To add health check for faiss inline vector_io provider (#2319)

# What does this PR do?
<!-- Provide a short summary of what this PR does and why. Link to
relevant issues if applicable. -->
To add health check for faiss inline vector_io provider.

I tried adding `async def health(self) -> HealthResponse:` like in
inference provider, but it didn't worked for `inline->vector_io->faiss`
provider. And via debug logs, I understood the critical issue, that the
health responses are being stored with the API name as the key, not as a
nested dictionary with provider IDs. This means that all providers of
the same API type (e.g., "vector_io") will share the same health
response, and only the last one processed will be visible in the API
response.
I've created a patch file that fixes this issue by:
- Storing the original get_providers_health method
- Creating a patched version that correctly maps health responses to
providers
- Applying the patch to the `ProviderImpl` class

Not an expert, so please let me know, if there can be any other
workaround using which I can get the health status updated directly from
`faiss.py`.

<!-- If resolving an issue, uncomment and update the line below -->
<!-- Closes #[issue-number] -->

## Test Plan
<!-- Describe the tests you ran to verify your changes with result
summaries. *Provide clear instructions so the plan can be easily
re-executed.* -->
Added unit tests to test the provider patch implementation in the PR.
Adding a screenshot with the FAISS inline vector_io health status as
"OK"


![faiss_health_check](https://github.com/user-attachments/assets/d769e762-890c-41ea-a596-5e90951f79a4)

llama_stack/distribution/routers/vector_io.py

@@ -4,6 +4,7 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+import asyncio
 from typing import Any
 
 from llama_stack.apis.common.content_types import (
@@ -21,7 +22,7 @@ from llama_stack.apis.vector_io import (
 )
 from llama_stack.apis.vector_io.vector_io import VectorStoreChunkingStrategy, VectorStoreFileObject
 from llama_stack.log import get_logger
-from llama_stack.providers.datatypes import RoutingTable
+from llama_stack.providers.datatypes import HealthResponse, HealthStatus, RoutingTable
 
 logger = get_logger(name=__name__, category="core")
 
@@ -276,3 +277,26 @@ class VectorIORouter(VectorIO):
             attributes=attributes,
             chunking_strategy=chunking_strategy,
         )
+
+    async def health(self) -> dict[str, HealthResponse]:
+        health_statuses = {}
+        timeout = 1  # increasing the timeout to 1 second for health checks
+        for provider_id, impl in self.routing_table.impls_by_provider_id.items():
+            try:
+                # check if the provider has a health method
+                if not hasattr(impl, "health"):
+                    continue
+                health = await asyncio.wait_for(impl.health(), timeout=timeout)
+                health_statuses[provider_id] = health
+            except (asyncio.TimeoutError, TimeoutError):
+                health_statuses[provider_id] = HealthResponse(
+                    status=HealthStatus.ERROR,
+                    message=f"Health check timed out after {timeout} seconds",
+                )
+            except NotImplementedError:
+                health_statuses[provider_id] = HealthResponse(status=HealthStatus.NOT_IMPLEMENTED)
+            except Exception as e:
+                health_statuses[provider_id] = HealthResponse(
+                    status=HealthStatus.ERROR, message=f"Health check failed: {str(e)}"
+                )
+        return health_statuses

llama_stack/providers/inline/vector_io/faiss/faiss.py

@@ -24,7 +24,11 @@ from llama_stack.apis.vector_io import (
     QueryChunksResponse,
     VectorIO,
 )
-from llama_stack.providers.datatypes import VectorDBsProtocolPrivate
+from llama_stack.providers.datatypes import (
+    HealthResponse,
+    HealthStatus,
+    VectorDBsProtocolPrivate,
+)
 from llama_stack.providers.utils.kvstore import kvstore_impl
 from llama_stack.providers.utils.kvstore.api import KVStore
 from llama_stack.providers.utils.memory.openai_vector_store_mixin import OpenAIVectorStoreMixin
@@ -175,6 +179,22 @@ class FaissVectorIOAdapter(OpenAIVectorStoreMixin, VectorIO, VectorDBsProtocolPr
         # Cleanup if needed
         pass
 
+    async def health(self) -> HealthResponse:
+        """
+        Performs a health check by verifying connectivity to the inline faiss DB.
+        This method is used by the Provider API to verify
+        that the service is running correctly.
+        Returns:
+
+            HealthResponse: A dictionary containing the health status.
+        """
+        try:
+            vector_dimension = 128  # sample dimension
+            faiss.IndexFlatL2(vector_dimension)
+            return HealthResponse(status=HealthStatus.OK)
+        except Exception as e:
+            return HealthResponse(status=HealthStatus.ERROR, message=f"Health check failed: {str(e)}")
+
     async def register_vector_db(
         self,
         vector_db: VectorDB,