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fix: drain entire queue per flush to avoid streaming tail lag #424

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fix: drain entire queue per flush to avoid streaming tail lag #424

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8 changes: 3 additions & 5 deletions ...ies/Microsoft.Teams.Plugins/Microsoft.Teams.Plugins.AspNetCore/AspNetCorePlugin.Stream.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -134,11 +134,10 @@ protected async Task Flush()
_timeout = null;
}

var i = 0;

Queue<TypingActivity> informativeUpdates = new();
var startCount = _queue.Count;
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Copilot AI Apr 13, 2026

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ConcurrentQueue<T>.Count can be O(n) and is an imprecise snapshot under concurrency. Since this value is only used to decide whether to return, it’s more efficient and accurate to avoid Count entirely and instead track a local dequeued counter (or a boolean flag) while draining.

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while (i <= 10 && _queue.TryDequeue(out var activity))
while (_queue.TryDequeue(out var activity))
{
if (activity is MessageActivity message)
{
Expand All @@ -159,11 +158,10 @@ protected async Task Flush()
informativeUpdates.Enqueue(typing);
}

i++;
_count++;
}

if (i == 0) return;
if (startCount == 0) return;
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Copilot AI Apr 13, 2026

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startCount is computed from _queue.Count, which is not a reliable indicator of whether this flush actually dequeued items in concurrent scenarios. If _queue.Count is 0 at line 138 but items are enqueued immediately after and then dequeued in the loop, startCount == 0 will still be true and the method will return early, potentially dropping/defering sends even though activities were drained and _count was incremented. Prefer tracking whether anything was actually dequeued (e.g., var dequeued = 0; increment inside the loop and if (dequeued == 0) return;), which matches the previous i == 0 behavior and avoids reliance on _queue.Count.

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// Send informative updates
if (informativeUpdates.Count > 0)
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