Fix memory leak from undisposed sockets and event handler retention during server restart#3608
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marcschier merged 4 commits intoMar 11, 2026
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…uring server restart When an OPC UA server is stopped and restarted in-process, TcpServerChannel instances were never garbage collected because UaSCBinaryChannel.Dispose() did not close the underlying socket. Pending ReceiveAsync operations kept the channels pinned via SocketAsyncEngine, causing a steady heap growth per cycle. Changes: - Close socket in UaSCBinaryChannel.Dispose() to cancel pending async I/O - Unsubscribe CertificateValidator.CertificateUpdate in StandardServer.Dispose() - Unsubscribe ConfigurationWatcher.Changed in StandardServer.Dispose() - Unsubscribe ConnectionStatusChanged from TransportListeners in ServerBase.Dispose() Verified over 786 restart cycles with stable heap.
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## master #3608 +/- ##
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+ Coverage 51.86% 66.06% +14.19%
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marcschier
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Mar 10, 2026
jnsjll
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Mar 12, 2026
…uring server restart (OPCFoundation#3608) * Fix memory leak from undisposed sockets and retained event handlers during server restart When an OPC UA server is stopped and restarted in-process, TcpServerChannel instances were never garbage collected because UaSCBinaryChannel.Dispose() did not close the underlying socket. Pending ReceiveAsync operations kept the channels pinned via SocketAsyncEngine, causing a steady heap growth per cycle. Changes: - Close socket in UaSCBinaryChannel.Dispose() to cancel pending async I/O - Unsubscribe CertificateValidator.CertificateUpdate in StandardServer.Dispose() - Unsubscribe ConfigurationWatcher.Changed in StandardServer.Dispose() - Unsubscribe ConnectionStatusChanged from TransportListeners in ServerBase.Dispose() Verified over 786 restart cycles with stable heap. * Remove verbose comment * Remove redundant event unsubscribe before dispose * Remove duplicate CertificateUpdate unsubscribe (already existed in master)
mrsuciu
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Mar 19, 2026
…uring server restart (OPCFoundation#3608) * Fix memory leak from undisposed sockets and retained event handlers during server restart When an OPC UA server is stopped and restarted in-process, TcpServerChannel instances were never garbage collected because UaSCBinaryChannel.Dispose() did not close the underlying socket. Pending ReceiveAsync operations kept the channels pinned via SocketAsyncEngine, causing a steady heap growth per cycle. Changes: - Close socket in UaSCBinaryChannel.Dispose() to cancel pending async I/O - Unsubscribe CertificateValidator.CertificateUpdate in StandardServer.Dispose() - Unsubscribe ConfigurationWatcher.Changed in StandardServer.Dispose() - Unsubscribe ConnectionStatusChanged from TransportListeners in ServerBase.Dispose() Verified over 786 restart cycles with stable heap. * Remove verbose comment * Remove redundant event unsubscribe before dispose * Remove duplicate CertificateUpdate unsubscribe (already existed in master) (cherry picked from commit eae41a5)
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When an OPC UA server is stopped and restarted in-process (e.g. for configuration changes),
TcpServerChannelinstances from previous server lifetimes were never garbage collected, causing a steady heap growth per restart cycle.Root cause:
UaSCBinaryChannel.Dispose()did not close the underlyingSocket. PendingReceiveAsyncoperations kept the channels pinned viaSocketAsyncEngine, preventing GC of the entire channel object graph (certificate caches, protocol buffers, etc.).Changes
UaSCBinaryChannel.Dispose()— Close socket to cancel pending async I/O and allow GC of disposed channelsServerBase.Dispose()— UnsubscribeConnectionStatusChangedfrom transport listeners before disposing themVerification
Tested with an in-process server restart loop over 786 cycles (~17 hours). Without the fix, heap grew steadily (~15 KB/cycle). With the fix, heap stabilized at 80-81 MB after initial warmup and remained flat for the entire run.
Test plan
TcpServerChannelcount stays at active-only (3-5) instead of accumulatingNotes
Do I need to add tests for this?
Disclaimer: This bug has been found with hours of manual work with AI and my local OPC UA stress test application and should be safe - please review the changes as I don't really know the OPC UA code base in depth.