trying queue

lib/backend.py

@@ -5,7 +5,7 @@ import base64
 import subprocess
 import dataclasses
 import logging
-from asyncio import wait, sleep, gather, Semaphore, FIRST_COMPLETED, create_task
+from asyncio import wait, sleep, gather, Semaphore, FIRST_COMPLETED, create_task, get_running_loop
 from typing import Tuple, Awaitable, NoReturn, List, Union, Callable, Optional
 from functools import cached_property
 from distutils.util import strtobool
@@ -74,6 +74,11 @@ class Backend:
         self._pubkey = self._fetch_pubkey()
         self.__start_healthcheck: bool = False
 
+        # NEW: FIFO queue + worker count
+        self.request_queue: "asyncio.Queue[tuple[EndpointHandler[ApiPayload_T], web.Request, asyncio.Future]]" = asyncio.Queue()
+        # If parallel allowed, let multiple workers drain the queue (order preserved by FIFO per worker; overall start order is FIFO).
+        self._num_workers: int = 1 if not self.allow_parallel_requests else int(os.environ.get("WORKERS", "4"))
+
     @property
     def pubkey(self) -> Optional[RSA.RsaKey]:
         if self._pubkey is None:
@@ -95,9 +100,14 @@ class Backend:
         while True:
             handler, request, fut = await self.request_queue.get()
             try:
-                res = await self.__process_request(handler, request)
+                # Skip if already cancelled while waiting in the queue
+                if fut.cancelled():
+                    continue
+                res = await self.__process_enqueued_request(handler, request)
+                if not fut.cancelled():
                     fut.set_result(res)
             except Exception as e:
+                if not fut.cancelled():
                     fut.set_exception(e)
             finally:
                 self.request_queue.task_done()
@@ -138,7 +148,36 @@ class Backend:
         handler: EndpointHandler[ApiPayload_T],
         request: web.Request,
     ) -> Union[web.Response, web.StreamResponse]:
-        """use this function to forward requests to the model endpoint"""
+        """use this function to enqueue requests for FIFO processing"""
+        loop = get_running_loop()
+        fut: asyncio.Future = loop.create_future()
+
+        # If the client disconnects while waiting in the FIFO, cancel the future so the worker skips it
+        cancel_watch = create_task(request.wait_for_disconnection())
+        def _cancel_if_disconnected(_):
+            if not fut.done():
+                fut.cancel()
+        cancel_watch.add_done_callback(_cancel_if_disconnected)
+
+        try:
+            await self.request_queue.put((handler, request, fut))
+            return await fut
+        except asyncio.CancelledError:
+            # Propagate cancellation to ensure aiohttp doesn't expect a response body
+            raise
+        finally:
+            # Best-effort cleanup of the watcher
+            cancel_watch.cancel()
+
+    async def __process_enqueued_request(
+        self,
+        handler: EndpointHandler[ApiPayload_T],
+        request: web.Request,
+    ) -> Union[web.Response, web.StreamResponse]:
+        """
+        This contains the original __handle_request logic and is invoked by workers,
+        ensuring FIFO execution via asyncio.Queue.
+        """
         try:
             data = await request.json()
             auth_data, payload = handler.get_data_from_request(data)
@@ -146,8 +185,11 @@ class Backend:
             return web.json_response(data=e.message, status=422)
         except json.JSONDecodeError:
             return web.json_response(dict(error="invalid JSON"), status=422)
+
         workload = payload.count_workload()
-        request_metrics: RequestMetrics = RequestMetrics(request_idx=auth_data.request_idx, reqnum=auth_data.reqnum, workload=workload, status="Created")
+        request_metrics: RequestMetrics = RequestMetrics(
+            request_idx=auth_data.request_idx, reqnum=auth_data.reqnum, workload=workload, status="Created"
+        )
 
         async def cancel_api_call_if_disconnected() -> web.Response:
             await request.wait_for_disconnection()
@@ -188,6 +230,8 @@ class Backend:
         acquired = False
         try:
             self.metrics._request_start(request_metrics)
+
+            # Preserve existing semaphore behavior for serializing requests when requested
             if self.allow_parallel_requests is False:
                 log.debug(f"Waiting to aquire Sem for reqnum:{request_metrics.reqnum}")
                 await self.sem.acquire()
@@ -197,6 +241,7 @@ class Backend:
                 )
             else:
                 log.debug(f"Starting request for reqnum:{request_metrics.reqnum}")
+
             done, pending = await wait(
                 [
                     create_task(make_request()),
@@ -264,8 +309,14 @@ class Backend:
                 self.backend_errored(str(e))
 
     async def _start_tracking(self) -> None:
+        # Start the FIFO workers alongside existing loops
+        worker_tasks = tuple(self._worker() for _ in range(self._num_workers))
         await gather(
-            self.__read_logs(), self.metrics._send_metrics_loop(), self.__healthcheck(), self.metrics._send_delete_requests_loop()
+            self.__read_logs(),
+            self.metrics._send_metrics_loop(),
+            self.__healthcheck(),
+            self.metrics._send_delete_requests_loop(),
+            *worker_tasks,
         )
 
     def backend_errored(self, msg: str) -> None: