fix(signal): use FIFO eviction for sent-timestamp tracking - #3692
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Replace plain set with OrderedDict for _recent_sent_timestamps so that eviction always removes the oldest entry instead of an arbitrary one. The previous set.pop() could discard newer timestamps while keeping stale ones indefinitely, degrading echo-back filtering over time.
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Closing — minor edge case that rarely triggers in practice. |
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Summary
Signal's echo-back filter (
_recent_sent_timestamps) usesset.pop()to evict old entries when the set exceeds 50 items. Since Python sets are unordered,pop()removes an arbitrary element — it might evict the newest timestamp while keeping a stale one from hours ago. Over time this degrades the echo-back filter: legitimate sent timestamps get evicted early, causing the adapter to re-process its own outbound messages as inbound.Same class of bug as #3490 (email
_seen_uidsgrowing unbounded).Root Cause
set.pop()on line 626 ofgateway/platforms/signal.pydoesn't guarantee oldest-first eviction. Sets have no insertion order in their iteration/pop behavior, so the eviction is effectively random.Fix
Replace the plain
setwithcollections.OrderedDict(used as an ordered set withNonevalues):set()→OrderedDict().discard(ts)→.pop(ts, None).add(ts)→[ts] = None,.pop()→.popitem(last=False)OrderedDict.popitem(last=False)always removes the oldest entry — O(1), deterministic FIFO.Tests
6 new tests in
tests/gateway/test_signal_timestamp_eviction.py:38 pre-existing signal tests + 6 new = 44 passed.