2 Commits

Author	SHA1	Message	Date
Marc Schier	889572472f	Convert DataValue from class to readonly struct for further GC relief (#3796) ... Convert `DataValue` from a mutable reference type (`class`) to a `readonly struct` to eliminate per-allocation GC pressure on every attribute read, subscription publish, and history sample. ### Key API changes (user-visible) | Before | After | Pattern | |---|---|---| | `class DataValue` | `readonly struct DataValue : INullable` | Foundation | | `Equals(DataValue?)` / `operator ==(DataValue?, DataValue?)` | `Equals(DataValue)` / `operator ==(DataValue, DataValue)` | Value semantics | | `IEncoder.WriteDataValue(string?, DataValue?)` | `IEncoder.WriteDataValue(string?, DataValue)` | Non-nullable wire API | | `IDecoder.ReadDataValue(...) -> DataValue?` | `IDecoder.ReadDataValue(...) -> DataValue` | Same | | `IDataChangeMonitoredItemQueue.PeekLast/Oldest()` | `TryPeekLastValue/Oldest(out DataValue)` | TryGet pattern | | `IAggregateCalculator.GetProcessedValue(bool)` | `TryGetProcessedValue(bool, out DataValue)` | Same | | `IUaPubSubDataStore.ReadPublishedDataItem(...)` | `TryReadPublishedDataItem(NodeId, uint, out DataValue)` | Same | | `Dictionary<uint, DataValue?>` (NodeCacheContext) | `Dictionary<uint, DataValue>` | Default + IsNull | | `IHistoryDataSource.FirstRaw/NextRaw` | `TryFirstRaw/TryNextRaw(out DataValue)` | TryGet pattern | | `NodeState.ReadAttribute(... DataValue)` | `NodeState.ReadAttribute(... ref DataValue)` | Sync mutation via ref | | `NodeState.ReadAttributeAsync(... DataValue)` | `NodeState.ReadAttributeAsync(...) -> ValueTask<(ServiceResult, DataValue)>` | Async return tuple | | `obj as DataValue` (heterogeneous Dictionary<string, object>) | `obj is DataValue dv ? dv : default(DataValue)` | Safe struct cast | | `Assert.That(dv, Is.Not.Null)` (tests) | `Assert.That(dv.IsNull, Is.False)` | Struct test pattern | | `[Obsolete] Value` setter, all property setters | Removed; use ctor or `With*()` | Immutability | | `[DataContract]` + `[DataMember]` | Removed; surrogate via `SerializableDataValue` + `DataValueSurrogateProvider` | Serialization | ### Wire format Wire format is **byte-identical** to the previous class-based implementation across binary / JSON / XML encoders. Default DataValue (`.IsNull == true`) is treated as the equivalent of the old null reference (writes JSON `null`, binary `byte 0`, XML omitted element). ### Why TryGet pattern (instead of leaving `DataValue?`) For methods that previously returned `DataValue?` to signal "no value available" (queue peek, aggregate result, data store lookup, history navigation), the conversion to `bool TryGet(out DataValue)` matches BCL conventions (`Dictionary.TryGetValue`, `Queue.TryPeek`, `Int32.TryParse`) and gives the caller an explicit "may be absent" affordance without `Nullable<DataValue>` overhead. ### Breaking changes summary - `DataValue` is now a `readonly struct` - boxing/unboxing semantics change for callers using `object`-typed APIs. - `IEncoder.WriteDataValue` / `IDecoder.ReadDataValue` / `ReadDataValueArray` interface signatures lose the `Nullable` wrapper. - `IDataChangeMonitoredItemQueue.PeekLastValue` / `PeekOldestValue` -> `TryPeekLastValue` / `TryPeekOldestValue` (out parameter). - `IAggregateCalculator.GetProcessedValue` -> `TryGetProcessedValue` (out parameter). - `IUaPubSubDataStore.ReadPublishedDataItem` -> `TryReadPublishedDataItem` (out parameter). - `NodeState.ReadAttribute` takes `ref DataValue`; `ReadAttributeAsync` returns `ValueTask<(ServiceResult, DataValue)>`. - `DataValue` property setters removed (use constructor + `With*` mutators).	2026-05-23 11:38:49 +02:00
Marc Schier	239a40b183	GC reduction via IPooledEncodeable activator pooling (#3793) ... * GC reduction via IPooledEncodeable activator pooling Add opt-in activator-level pooling for IEncodeable instances decoded during V2 subscription publish dispatch. The design replaces the earlier IAllocator-on-IServiceMessageContext approach (which had a cross-contamination hazard for non-publish decodes) with a clean factory-based model where pooling lives on the encodeable activator. New public API: - IPooledEncodeable : IEncodeable - opt-in marker with Reuse() method - PooledEncodeableType<T> : EncodeableType<T> - activator base with BoundedObjectPool<T> (lock-free, no new package dependency) - ISubscriptionManager.PoolNotifications { get; set; } - ManagedSessionOptions.PoolNotifications { get; init; } - ManagedSessionBuilder.WithPoolNotifications(bool) Source-gen: - All concrete non-abstract structure types (including service request/response types) are generated with PooledEncodeableType<T> activators and IPooledEncodeable.Reuse() bodies by default - Derived types use 'new' to hide inherited Reuse/ClearPooledSentinel so each concrete type routes through its own activator's pool - No changes to external design XML files (UA Core Services.xml etc.) - poolable selection is hardcoded in the generator Benchmarks (MonitoredItemNotification, 1000 ops): - Allocations: 128 KB -> 408 B (~315x reduction) - Gen0 collections: 29.75 -> 0.09 per 1000 ops No interface changes to IEncodeable, IDecoder, IServiceMessageContext, or ISubscriptionNotificationHandler. Handlers retain by copy when pooling is enabled. Call IPooledEncodeable.Reuse() on decoded IServiceRequest and IServiceResponse after the server is done with them: - TcpTransportListener.OnRequestReceivedAsync: reuse both request and response in a finally block after ProcessRequestAsync + SendResponse complete - EndpointBase.InvokeServiceAsync (HTTPS path): same pattern after ProcessRequestAsync + BinaryEncoder.EncodeMessage Walk acknowledged, overflow-evicted, and disposed NotificationMessage objects and call IPooledEncodeable.Reuse() on their notification payloads (MonitoredItemNotification, DataChangeNotification, EventFieldList, EventNotificationList). Insertion points in Subscription.cs: - Acknowledge(): after RemoveAt from m_sentMessages - InnerPublish() overflow: before RemoveRange/Clear on m_sentMessages - Dispose(): before m_sentMessages.Clear() - InnerPublish() unsent-message overflow: before RemoveRange on the messages list Replace new T() with XxxActivator.Instance.CreateInstance() for all server-side notification payload types so instances are rented from the activator pool instead of heap-allocated: New static helper ReuseNotificationPayloads() walks the NotificationMessage.NotificationData, extracts DataChangeNotification and EventNotificationList via TryGetValue, iterates their items, and calls Reuse() on each pooled payload.	2026-05-22 12:42:33 +02:00