Server embedder: use queue, handle unsuccessful requests at the end

Author: PrimozGodec

Orange/misc/server_embedder.py

@@ -3,29 +3,30 @@
 import logging
 import random
 import uuid
+from collections import namedtuple
 from json import JSONDecodeError
 from os import getenv
 from typing import Any, Callable, List, Optional
 
 from AnyQt.QtCore import QSettings
 from httpx import AsyncClient, NetworkError, ReadTimeout, Response
 
-from Orange.misc.utils.embedder_utils import (EmbedderCache,
-                                              EmbeddingCancelledException,
-                                              EmbeddingConnectionError,
-                                              get_proxies)
+from Orange.misc.utils.embedder_utils import (
+    EmbedderCache,
+    EmbeddingCancelledException,
+    EmbeddingConnectionError,
+    get_proxies,
+)
 
 log = logging.getLogger(__name__)
+TaskItem = namedtuple("TaskItem", ("id", "item", "no_repeats"))
 
 
 class ServerEmbedderCommunicator:
     """
     This class needs to be inherited by the class which re-implements
-    _encode_data_instance and defines self.content_type. For sending a table
-    with data items use embedd_table function. This one is called with the
-    complete Orange data Table. Then _encode_data_instance needs to extract
-    data to be embedded from the RowInstance. For images, it takes the image
-    path from the table, load image, and transform it into bytes.
+    _encode_data_instance and defines self.content_type. For sending a list
+    with data items use embedd_table function.
 
     Attributes
     ----------
@@ -69,14 +70,14 @@ def __init__(
             ) or str(uuid.getnode())
         except TypeError:
             self.machine_id = str(uuid.getnode())
-        self.session_id = str(random.randint(1, 1e10))
+        self.session_id = str(random.randint(1, int(1e10)))
 
         self._cache = EmbedderCache(model_name)
 
         # default embedding timeouts are too small we need to increase them
         self.timeout = 180
-        self.num_parallel_requests = 0
-        self.max_parallel = max_parallel_requests
+        self.max_parallel_requests = max_parallel_requests
+
         self.content_type = None  # need to be set in a class inheriting
 
     def embedd_data(
@@ -111,8 +112,7 @@ def embedd_data(
         EmbeddingCancelledException:
             If cancelled attribute is set to True (default=False).
         """
-        # if there is less items than 10 connection error should be raised
-        # earlier
+        # if there is less items than 10 connection error should be raised earlier
         self.max_errors = min(len(data) * self.MAX_REPEATS, 10)
 
         loop = asyncio.new_event_loop()
@@ -121,11 +121,9 @@ def embedd_data(
             embeddings = asyncio.get_event_loop().run_until_complete(
                 self.embedd_batch(data, processed_callback)
             )
-        except Exception:
+        finally:
             loop.close()
-            raise
 
-        loop.close()
         return embeddings
 
     async def embedd_batch(
@@ -153,32 +151,63 @@ async def embedd_batch(
         EmbeddingCancelledException:
             If cancelled attribute is set to True (default=False).
         """
-        requests = []
+        results = [None] * len(data)
+        queue = asyncio.Queue()
+
+        # fill the queue with items to embedd
+        for i, item in enumerate(data):
+            queue.put_nowait(TaskItem(id=i, item=item, no_repeats=0))
+
         async with AsyncClient(
-                timeout=self.timeout, base_url=self.server_url, proxies=get_proxies()
+            timeout=self.timeout, base_url=self.server_url, proxies=get_proxies()
         ) as client:
-            for p in data:
-                if self._cancelled:
-                    raise EmbeddingCancelledException()
-                requests.append(self._send_to_server(p, client, proc_callback))
+            tasks = self._init_workers(client, queue, results, proc_callback)
+
+            # wait for the queue to complete or one of workers to exit
+            queue_complete = asyncio.create_task(queue.join())
+            await asyncio.wait(
+                [queue_complete, *tasks], return_when=asyncio.FIRST_COMPLETED
+            )
+
+        # Cancel worker tasks when done
+        queue_complete.cancel()
+        await self._cancel_workers(tasks)
 
-            embeddings = await asyncio.gather(*requests)
         self._cache.persist_cache()
-        assert self.num_parallel_requests == 0
+        return results
 
-        return embeddings
+    def _init_workers(self, client, queue, results, callback):
+        """Init required number of workers"""
+        t = [
+            asyncio.create_task(self._send_to_server(client, queue, results, callback))
+            for _ in range(self.max_parallel_requests)
+        ]
+        log.debug("Created %d workers", self.max_parallel_requests)
+        return t
 
-    async def __wait_until_released(self) -> None:
-        while self.num_parallel_requests >= self.max_parallel:
-            await asyncio.sleep(0.1)
+    @staticmethod
+    async def _cancel_workers(tasks):
+        """Cancel worker at the end"""
+        log.debug("Canceling workers")
+        try:
+            # try to catch any potential exceptions
+            await asyncio.gather(*tasks)
+        except Exception as ex:
+            # raise exceptions gathered from an failed worker
+            raise ex
+        finally:
+            # cancel all tasks in both cases
+            for task in tasks:
+                task.cancel()
+            # Wait until all worker tasks are cancelled.
+            await asyncio.gather(*tasks, return_exceptions=True)
+            log.debug("All workers canceled")
 
     def __check_cancelled(self):
         if self._cancelled:
             raise EmbeddingCancelledException()
 
-    async def _encode_data_instance(
-            self, data_instance: Any
-    ) -> Optional[bytes]:
+    async def _encode_data_instance(self, data_instance: Any) -> Optional[bytes]:
         """
         The reimplementation of this function must implement the procedure
         to encode the data item in a string format that will be sent to the
@@ -197,63 +226,74 @@ async def _encode_data_instance(
         raise NotImplementedError
 
     async def _send_to_server(
-            self,
-            data_instance: Any,
-            client: AsyncClient,
-            proc_callback: Callable[[bool], None] = None,
-    ) -> Optional[List[float]]:
+        self,
+        client: AsyncClient,
+        queue: asyncio.Queue,
+        results: List,
+        proc_callback: Callable[[bool], None] = None,
+    ):
         """
-        Function get an data instance. It extract data from it and send them to
-        server and retrieve responses.
+        Worker that embedds data. It is pulling items from the until the queue
+        is empty. It is canceled by embedd_batch all tasks are finished
 
         Parameters
         ----------
-        data_instance
-            Single row of the input table.
         client
             HTTPX client that communicates with the server
+        queue
+            The queue with items of type TaskItem to be embedded
+        results
+            The list to append results in. The list has length equal to numbers
+            of all items to embedd. The result need to be inserted at the index
+            defined in queue items.
         proc_callback
             A function that is called after each item is fully processed
             by either getting a successful response from the server,
             getting the result from cache or skipping the item.
-
-        Returns
-        -------
-        Embedding. For items that are not successfully embedded returns None.
         """
-        await self.__wait_until_released()
-        self.__check_cancelled()
-
-        self.num_parallel_requests += 1
-        # load bytes
-        data_bytes = await self._encode_data_instance(data_instance)
-        if data_bytes is None:
-            self.num_parallel_requests -= 1
-            return None
-
-        # if data in cache return it
-        cache_key = self._cache.md5_hash(data_bytes)
-        emb = self._cache.get_cached_result_or_none(cache_key)
-
-        if emb is None:
-            # in case that embedding not sucessfull resend it to the server
-            # maximally for MAX_REPEATS time
-            for i in range(1, self.MAX_REPEATS + 1):
-                self.__check_cancelled()
+        while not queue.empty():
+            self.__check_cancelled()
+
+            # get item from the queue
+            i, data_instance, num_repeats = await queue.get()
+            num_repeats += 1
+
+            # load bytes
+            data_bytes = await self._encode_data_instance(data_instance)
+            if data_bytes is None:
+                continue
+
+            # retrieve embedded item from the local cache
+            cache_key = self._cache.md5_hash(data_bytes)
+            log.debug("Embedding %s", cache_key)
+            emb = self._cache.get_cached_result_or_none(cache_key)
+
+            if emb is None:
+                # send the item to the server for embedding if not in the local cache
+                log.debug("Sending to the server: %s", cache_key)
                 url = (
-                    f"/{self.embedder_type}/{self._model}?"
-                    f"machine={self.machine_id}"
-                    f"&session={self.session_id}&retry={i}"
+                    f"/{self.embedder_type}/{self._model}?machine={self.machine_id}"
+                    f"&session={self.session_id}&retry={num_repeats}"
                 )
                 emb = await self._send_request(client, data_bytes, url)
                 if emb is not None:
                     self._cache.add(cache_key, emb)
-                    break  # repeat only when embedding None
-        if proc_callback:
-            proc_callback(emb is not None)
 
-        self.num_parallel_requests -= 1
-        return emb
+            if emb is not None:
+                # store result if embedding is successful
+                log.debug("Successfully embedded:  %s", cache_key)
+                results[i] = emb
+                if proc_callback:
+                    proc_callback(emb is not None)
+            elif num_repeats < self.MAX_REPEATS:
+                log.debug("Embedding unsuccessful - reading to queue:  %s", cache_key)
+                # if embedding not successful put the item to queue to be handled at
+                # the end - the item is put to the end since it is possible that  server
+                # still process the request and the result will be in the cache later
+                # repeating the request immediately may result in another fail when
+                # processing takes longer
+                queue.put_nowait(TaskItem(i, data_instance, no_repeats=num_repeats))
+            queue.task_done()
 
     async def _send_request(
             self, client: AsyncClient, data: bytes, url: str
@@ -284,27 +324,23 @@ async def _send_request(
             response = await client.post(url, headers=headers, data=data)
         except ReadTimeout as ex:
             log.debug("Read timeout", exc_info=True)
-            # it happens when server do not respond in 60 seconds, in
-            # this case we return None and items will be resend later
+            # it happens when server do not respond in time defined by timeout
+            # return None and items will be resend later
 
             # if it happens more than in ten consecutive cases it means
             # sth is wrong with embedder we stop embedding
             self.count_read_errors += 1
-
             if self.count_read_errors >= self.max_errors:
-                self.num_parallel_requests = 0  # for safety reasons
                 raise EmbeddingConnectionError from ex
             return None
         except (OSError, NetworkError) as ex:
             log.debug("Network error", exc_info=True)
-            # it happens when no connection and items cannot be sent to the
-            # server
-            # we count number of consecutive errors
+            # it happens when no connection and items cannot be sent to server
+
             # if more than 10 consecutive errors it means there is no
             # connection so we stop embedding with EmbeddingConnectionError
             self.count_connection_errors += 1
             if self.count_connection_errors >= self.max_errors:
-                self.num_parallel_requests = 0  # for safety reasons
                 raise EmbeddingConnectionError from ex
             return None
         except Exception:

Orange/misc/tests/test_server_embedder.py

@@ -167,3 +167,12 @@ def test_encode_data_instance(self):
         mocked_fun.assert_has_calls(
             [call(item) for item in self.test_data], any_order=True
         )
+
+    @patch(_HTTPX_POST_METHOD, return_value=DummyResponse(b''))
+    def test_retries(self, mock):
+        self.embedder.embedd_data(self.test_data)
+        self.assertEqual(len(self.test_data) * 3, mock.call_count)
+
+
+if __name__ == "__main__":
+    unittest.main()