Addressing:

• Optimize synapse/handlers/federation_event.py#L545(backfill receiving) to be more efficient. Calculate the stream_ordering from newest -> oldest (in the correct order) and persist in the oldest -> newest to get the least missing prev_event fetch thrashing
  • Spawned from Fix historical messages backfilling in random order on remote homeservers (MSC2716) #11114 (comment)
  • Why aren't we sorting topologically when receiving backfill events? See Fix historical messages backfilling in random order on remote homeservers (MSC2716) #11114 (comment)

-- #10737

So Synapse is fast enough to merge this MSC2716 Complement test for importing many batches, matrix-org/complement#214 (comment)

Complement tests: matrix-org/complement#214

Spawned from scratch changes in, #13864

Dev notes

pseudo_events = [
    { "event": 'eventBefore1', "depth": 1 },
    { "event": 'eventBefore2', "depth": 2 },
    { "event": 'Historical message 1', "depth": 3 },
    { "event": 'Historical message 2', "depth": 3 },
    { "event": 'Historical message 3', "depth": 3 },
    { "event": 'eventAfter1', "depth": 3 },
    { "event": 'eventAfter2', "depth": 4 }
]

pseudo_events = [
    { "event": 'eventAfter2', "depth": 4 },
    { "event": 'eventAfter1', "depth": 3 },
    { "event": 'Historical message 3', "depth": 3 },
    { "event": 'Historical message 2', "depth": 3 },
    { "event": 'Historical message 1', "depth": 3 },
    { "event": 'eventBefore2', "depth": 2 },
    { "event": 'eventBefore1', "depth": 1 },
]


sorted_events = [u[1] for u in sorted(
    enumerate(pseudo_events), key=lambda x: (-x[1].get("depth"), x[0])
)]

print(json.dumps(sorted_events, indent=4))

Pull Request Checklist

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