From 77156a4bc1f87e98754e3f7f86e52a84a4253a10 Mon Sep 17 00:00:00 2001
From: Eric Eastwood <erice@element.io>
Date: Wed, 24 May 2023 23:22:24 -0500
Subject: Process previously failed backfill events in the background (#15585)

Process previously failed backfill events in the background because they are bound to fail again and we don't need to waste time holding up the request for something that is bound to fail again.

Fix https://github.com/matrix-org/synapse/issues/13623

Follow-up to https://github.com/matrix-org/synapse/issues/13621 and https://github.com/matrix-org/synapse/issues/13622

Part of making `/messages` faster: https://github.com/matrix-org/synapse/issues/13356
---
 synapse/util/iterutils.py | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

(limited to 'synapse/util')

diff --git a/synapse/util/iterutils.py b/synapse/util/iterutils.py
index 4938ddf703..a0efb96d3b 100644
--- a/synapse/util/iterutils.py
+++ b/synapse/util/iterutils.py
@@ -15,11 +15,13 @@
 import heapq
 from itertools import islice
 from typing import (
+    Callable,
     Collection,
     Dict,
     Generator,
     Iterable,
     Iterator,
+    List,
     Mapping,
     Set,
     Sized,
@@ -71,6 +73,31 @@ def chunk_seq(iseq: S, maxlen: int) -> Iterator[S]:
     return (iseq[i : i + maxlen] for i in range(0, len(iseq), maxlen))
 
 
+def partition(
+    iterable: Iterable[T], predicate: Callable[[T], bool]
+) -> Tuple[List[T], List[T]]:
+    """
+    Separate a given iterable into two lists based on the result of a predicate function.
+
+    Args:
+        iterable: the iterable to partition (separate)
+        predicate: a function that takes an item from the iterable and returns a boolean
+
+    Returns:
+        A tuple of two lists, the first containing all items for which the predicate
+        returned True, the second containing all items for which the predicate returned
+        False
+    """
+    true_results = []
+    false_results = []
+    for item in iterable:
+        if predicate(item):
+            true_results.append(item)
+        else:
+            false_results.append(item)
+    return true_results, false_results
+
+
 def sorted_topologically(
     nodes: Iterable[T],
     graph: Mapping[T, Collection[T]],
-- 
cgit 1.5.1