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[Client] Fixed freezing of Subscription with sequential publishing #3565

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Merged
marcschier merged 3 commits into from
Feb 28, 2026
Merged

[Client] Fixed freezing of Subscription with sequential publishing #3565

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f7c9ba9
[Client] Fixed freezing of Subscription with sequential publishing
AnatolyKochnev Feb 17, 2026
7e70326
[PR] fix naming convention violation
AnatolyKochnev Feb 19, 2026
45fe9c6
[PR] removed region in tests
AnatolyKochnev Feb 24, 2026
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36 changes: 32 additions & 4 deletions Libraries/Opc.Ua.Client/Subscription/Subscription.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,9 +46,13 @@ public class Subscription : ISnapshotRestore<SubscriptionState>, IDisposable, IC
{
private const int kMinKeepAliveTimerInterval = 1000;
private const int kKeepAliveTimerMargin = 1000;
private const int kRepublishMessageTimeout = 2500;
private const int kRepublishMessageExpiredTimeout = 10000;

/// <summary>
/// Duration to wait before republishing missed notification
/// </summary>
public const int REPUBLISH_MESSAGE_TIMEOUT = 2500;
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/// <summary>
/// Create subscription
/// </summary>
Expand Down Expand Up @@ -1619,9 +1623,33 @@ public void SaveMessageInCache(

// fill in any gaps in the queue
LinkedListNode<IncomingMessage>? node = m_incomingMessages.First;
if (node is not null)
{
//gaps between m_lastSequenceNumberProcessed and starting node
LinkedListNode<IncomingMessage> currentNode = node;
for (uint i = node.Value.SequenceNumber; i > (m_lastSequenceNumberProcessed + 1); i--)
{
var placeholder = new IncomingMessage
{
SequenceNumber = i - 1,
Timestamp = now,
TickCount = tickCount
};
currentNode = m_incomingMessages.AddBefore(currentNode, placeholder);

m_logger.LogInformation(
"Session {SessionId}, subscription {SubscriptionName} ({SubscriptionId}): " +
"added placeholder for missing incoming message with sequence number {MissingSequenceNumber}",
Session?.SessionId,
DisplayName,
Id,
placeholder.SequenceNumber);
}
}

while (node != null)
{
//gaps between neighbouring nodes
entry = node.Value;
LinkedListNode<IncomingMessage>? next = node.Next;

Expand Down Expand Up @@ -1969,8 +1997,8 @@ private void ProcessTransferredSequenceNumbers(UInt32Collection availableSequenc
// only republish consecutive sequence numbers
// triggers the republish mechanism immediately,
// if event is in the past
DateTime now = DateTime.UtcNow.AddMilliseconds(-kRepublishMessageTimeout * 2);
int tickCount = HiResClock.TickCount - (kRepublishMessageTimeout * 2);
DateTime now = DateTime.UtcNow.AddMilliseconds(-REPUBLISH_MESSAGE_TIMEOUT * 2);
int tickCount = HiResClock.TickCount - (REPUBLISH_MESSAGE_TIMEOUT * 2);
uint lastSequenceNumberToRepublish = m_lastSequenceNumberProcessed - 1;
int availableNumbers = availableSequenceNumbers.Count;
int republishMessages = 0;
Expand Down Expand Up @@ -2505,7 +2533,7 @@ private async Task OnMessageReceivedAsync(CancellationToken ct)
// tolerate if a single request was received out of order
if (ii.Next.Next != null &&
(HiResClock.TickCount -
ii.Value.TickCount) > kRepublishMessageTimeout)
ii.Value.TickCount) > REPUBLISH_MESSAGE_TIMEOUT)
{
ii.Value.Republished = true;
publishStateChangedMask |= PublishStateChangedMask.Republish;
Expand Down
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