# Description
This pull request introduces a scalable consumer task model for the
`MonitoredNode2` class, optimizing the handling of event notifications
for notifier nodes. Any notifier node can opt into (or out of) dynamic
scaling of consumer tasks based on the number of event monitored items,
improving throughput and responsiveness under high event loads. The
Server node (`ObjectIds.Server`) is always auto-opted-in. The
implementation includes safe scaling up and down of consumers, robust
disposal logic, Fluent API integration, and tests to verify correct
delivery of events.
**Scalable consumer task management:**
* Added an `enableMultipleEventConsumers` constructor parameter to
`MonitoredNode2` that enables dynamic scaling of consumer tasks to match
the number of event monitored items. The Server node
(`ObjectIds.Server`) always auto-opts-in regardless of this parameter.
* Added `AllowMultipleEventConsumers(NodeId, bool enable = true)`
protected method on `AsyncCustomNodeManager` with an internal
`MultiConsumerNodeIds` registry, so any node manager can
programmatically opt in or out specific nodes.
* Added `IsMultipleEventConsumerNode(NodeId)` to the `IAsyncNodeManager`
interface, allowing consumers to query multi-consumer opt-in status
through the interface without casting to `AsyncCustomNodeManager`.
* Both `MonitoredNodeMonitoredItemManager` and
`SamplingGroupMonitoredItemManager` use the `IAsyncNodeManager`
interface method when creating `MonitoredNode2` instances.
**Fluent API integration:**
* Added `AllowMultipleEventConsumers(bool enable = true)` method to
`INodeBuilder` and its `NodeBuilder` implementation, allowing any
notifier node to be opted in or out via the fluent builder pipeline
(e.g. `builder.Node("myNotifier").AllowMultipleEventConsumers()`).
* The `NodeManagerBuilder` routes the registration to the owning
`AsyncCustomNodeManager`'s multi-consumer registry, supporting both
opt-in and opt-out.
**Testing and verification:**
* Added unit tests to verify multi-consumer behavior for both Server
node (auto-opt-in) and non-Server nodes (explicit opt-in), as well as
default single-consumer behavior for nodes without opt-in.
* Fixed race condition in permission cache tests
(`OnMonitoredNodeChanged_DefaultPermissionsChanged_CacheInvalidated` and
`InvalidatePermissionCacheForSession` tests) that caused flaky CI
failures. The tests now signal on `QueueValue` (which fires after the
cache is populated) instead of `ValidateRolePermissionsAsync` (which
fires before), ensuring cache invalidation operates on a populated
cache.
## Related Issues
## Checklist
- [ ] I have signed the
[CLA](https://opcfoundation.org/license/cla/ContributorLicenseAgreementv1.0.pdf)
and read the
[CONTRIBUTING](https://github.com/OPCFoundation/UA-.NETStandard/blob/master/CONTRIBUTING.md)
doc.
- [x] I have added tests that prove my fix is effective or that my
feature works and increased code coverage.
- [ ] I have added all necessary documentation.
- [x] I have verified that my changes do not introduce (new) build or
analyzer warnings.
- [ ] I ran **all** tests locally using the **UA.slnx** solution against
at least .net **framework** and .net **10**, and all passed.
- [x] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
- [x] I have addressed **all** PR feedback received.
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
## Proposed changes
This PR updates the server monitored-item pipeline to be
`IAsyncNodeManager`-aware and introduces channel-based FIFO queueing in
the monitored-node path to improve behavior under load.
It also includes follow-up fixes from review/CI feedback:
- Adjusted
`AsyncCustomNodeManagerTests.WriteAsync_PublishesValueToMonitoredItemQueueAsync`
to account for channel-based delivery timing/coalescing while still
asserting the written value is observed.
- Merged latest `master` into this branch and resolved merge conflicts
(notably in `ConfigurationNodeManager`), keeping async address-space
lookup behavior intact.
- Applied small compile-safety corrections needed for successful
validation.
Drive the solution to zero warnings / zero errors with analyzers on,
promote the consistently-fixed rules to error, and lock in coverage
on the only line of new logic.
* New certificate and secrete abstraction with certificate infrastructure and certificate/secret stores.
* leak testing for certificate resources to validate new ref counting in every test assembly
* Migration guide updated and documentation added for all
* Remove IDisposable from Nodestate and UserIdentity.
* UserCertificateTokenHandler now just points into certificate registry/stores, no dispose required
* Fix CA2000 warnings and cleanup of other diagnostics, increase warning levels in .editorconfig
* make most ptojects aot compatible
* Remove newtonsoft
* Migrate all projects from Mono.Options to System.CommandLine 2.0.5
* Fix array clone
* Replace serializers for storage using new attribute driven type geberator
* Add new AOT integration tests covering all functional areas
* Documentation updates
* Use Interfaces Introduced with 1.5.378
Refactor to use interfaces for node managers and server
Replaced concrete types with interfaces (e.g., IMasterNodeManager, ICoreNodeManager, IDiagnosticsNodeManager, IConfigurationNodeManager, IServerBase) across method signatures, properties, and internal structures to improve abstraction and flexibility.
* Refactor CoreNodeManager to be Based on CustomNodeManager2
* Add Test
* Add INodeManager3 with role permission validation
Introduce INodeManager3 interface extending INodeManager2, adding synchronous role permission validation methods. Update all node manager interfaces and classes to use INodeManager3. Extend IAsyncNodeManager with async permission validation methods and update adapters for sync/async bridging. Deprecate FindNodeInAddressSpace in favor of new async FindNodeInAddressSpaceAsync. Refactor MonitoredNode2 to use thread-safe collections and locking for monitored items. Enhance event reporting with security and permission checks. Update constructors and documentation to reflect new interfaces and best practices.
* fix comment
* fix
* Improve thread safety and logging in MonitoredItem
Replaced Queue with ConcurrentQueue in MonitoredItemDataCache
for thread-safe operations. Updated Publish method to use
List<DataValue> for better handling of dequeued values. Enhanced
logging to include SourceTime and added logs for dropped values.
In DurableSubscriptionTest, added try-finally block to ensure
proper session closure and disposal, preventing memory leaks.
Introduced DurableSubscriptionTestLooper for stress testing
under debug mode. Refactored test code for improved readability.
* Improve logging and session management
Updated logging in `Session.cs`, `ServerBase.cs`, and `UaSCBinaryClientChannel.cs` to pass exceptions directly to the logger, enhancing error handling. Added connection state checks in `Session.cs` to prevent operations when the session is closed or never connected. Updated `Subscription.cs` to reflect session disconnection in `PublishingStopped`. Enhanced test outputs and renamed `DurableSubscriptionTestLooper` to `DurableSubscriptionTestDebug` in `DurableSubscriptionTest.cs`, reducing loop count for faster debug testing.
* Fix monitored item id factory producing collisions by first trying to allocate a free monitored item id in the table, then committing.
* Better diffing
* Enhance logging and session management
Added detailed logging in `AlarmNodeManager.cs` for lifecycle events and simulation control. Introduced a `Reconnecting` property in the `ISession` interface and `Session.cs` to manage session reconnection state, replacing the `m_reconnecting` field. Enhanced logging in `Session.cs` for reconnection and publish operations. Updated `DataGenerator.cs` to use `FrozenDictionary` for performance improvements. Replaced `SyncRoot` with `m_syncRoot` in `NamespaceTable.cs` for synchronization. Improved exception message formatting in `ServiceResult.cs`. Added necessary namespaces for new data structures. Made corrections and added debugging in `DurableSubscriptionTest.cs` for better session handling.
* Dispose simulation
* extend MonitoredItem manager
* Update MonitoredItem List with event montiored items
* Update comments
* Add SetMonitoringMode function call to SubscriptionTest
* Enable use of Sampling Groups in Reference Node Manager
* set minimum sampling interval for Sampling Groups
* Dispose SamplingGroups on shutdown and cleanup
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