feat: Added thread pool limiter

- Configurable via `chroma_server_thread_pool_size` setting

chromadb/config.py

@@ -82,6 +82,7 @@
 DEFAULT_TENANT = "default_tenant"
 DEFAULT_DATABASE = "default_database"
 
+
 class Settings(BaseSettings):  # type: ignore
     environment: str = ""
 
@@ -139,6 +140,8 @@ def empty_str_to_none(cls, v: str) -> Optional[str]:
         return v
 
     chroma_server_nofile: Optional[int] = None
+    # the number of maximum threads to handle synchronous tasks in the FastAPI server
+    chroma_server_thread_pool_size: Optional[int] = 40
 
     pulsar_broker_url: Optional[str] = None
     pulsar_admin_port: Optional[int] = 8080
@@ -320,13 +323,16 @@ def __init__(self, settings: Settings):
             if settings[key] is not None:
                 raise ValueError(LEGACY_ERROR)
 
-        if settings["chroma_segment_cache_policy"] is not None and settings["chroma_segment_cache_policy"] != "LRU":
+        if (
+            settings["chroma_segment_cache_policy"] is not None
+            and settings["chroma_segment_cache_policy"] != "LRU"
+        ):
             logger.error(
-                f"Failed to set chroma_segment_cache_policy: Only LRU is available."
+                "Failed to set chroma_segment_cache_policy: Only LRU is available."
             )
             if settings["chroma_memory_limit_bytes"] == 0:
                 logger.error(
-                    f"Failed to set chroma_segment_cache_policy: chroma_memory_limit_bytes is require."
+                    "Failed to set chroma_segment_cache_policy: chroma_memory_limit_bytes is require."
                 )
 
         # Apply the nofile limit if set

chromadb/server/fastapi/__init__.py

@@ -5,6 +5,7 @@
 # https://anyio.readthedocs.io/en/stable/threads.html#adjusting-the-default-maximum-worker-thread-count
 from anyio import (
     to_thread,
+    CapacityLimiter,
 )  # this is used to transform sync code to async. By default, AnyIO uses 40 threads pool
 from fastapi import FastAPI as _FastAPI, Response, Request
 from fastapi.responses import JSONResponse
@@ -141,6 +142,8 @@ def __init__(self, settings: Settings):
         self._system = System(settings)
         self._api: ServerAPI = self._system.instance(ServerAPI)
         self._opentelemetry_client = self._api.require(OpenTelemetryClient)
+        self._thread_pool_size = settings.chroma_server_thread_pool_size
+        self._capacity_limiter = CapacityLimiter(self._thread_pool_size)
         self._system.start()
 
         self._app.middleware("http")(check_http_version_middleware)
@@ -487,7 +490,11 @@ async def delete_collection(
         database: str = DEFAULT_DATABASE,
     ) -> None:
         return await to_thread.run_sync(  # type: ignore
-            self._api.delete_collection, collection_name, tenant, database
+            self._api.delete_collection,
+            collection_name,
+            tenant,
+            database,
+            limiter=self._capacity_limiter,
         )
 
     @trace_method("FastAPI.add", OpenTelemetryGranularity.OPERATION)
@@ -511,6 +518,7 @@ async def add(self, request: Request, collection_id: str) -> None:
                 add.metadatas,
                 add.documents,
                 add.uris,
+                limiter=self._capacity_limiter,
             )
         except InvalidDimensionException as e:
             raise HTTPException(status_code=500, detail=str(e))
@@ -536,6 +544,7 @@ async def update(self, request: Request, collection_id: str) -> None:
             add.metadatas,
             add.documents,
             add.uris,
+            limiter=self._capacity_limiter,
         )
 
     @trace_method("FastAPI.upsert", OpenTelemetryGranularity.OPERATION)
@@ -559,6 +568,7 @@ async def upsert(self, request: Request, collection_id: str) -> None:
             upsert.metadatas,
             upsert.documents,
             upsert.uris,
+            limiter=self._capacity_limiter,
         )
 
     @trace_method("FastAPI.get", OpenTelemetryGranularity.OPERATION)
@@ -585,6 +595,7 @@ async def get(self, collection_id: str, get: GetEmbedding) -> GetResult:
                 None,
                 get.where_document,
                 get.include,
+                limiter=self._capacity_limiter,
             ),
         )
 
@@ -606,6 +617,7 @@ async def delete(self, collection_id: str, delete: DeleteEmbedding) -> List[UUID
                 delete.ids,
                 delete.where,
                 delete.where_document,
+                limiter=self._capacity_limiter,
             ),
         )
 
@@ -620,7 +632,10 @@ async def delete(self, collection_id: str, delete: DeleteEmbedding) -> List[UUID
     )
     async def count(self, collection_id: str) -> int:
         return cast(
-            int, await to_thread.run_sync(self._api._count, _uuid(collection_id))
+            int,
+            await to_thread.run_sync(
+                self._api._count, _uuid(collection_id), limiter=self._capacity_limiter
+            ),
         )
 
     @trace_method("FastAPI.reset", OpenTelemetryGranularity.OPERATION)
@@ -656,6 +671,7 @@ async def get_nearest_neighbors(
                 query.where,
                 query.where_document,
                 query.include,
+                limiter=self._capacity_limiter,
             ),
         )
         return nnresult