# Description
Adopt
[`System.TimeProvider`](https://learn.microsoft.com/dotnet/api/system.timeprovider)
across the stack so that every place that creates timers, runs duration
math, or schedules periodic work is mockable, deterministic in tests,
and immune to wall-clock changes.
The migration touches Core, Core.Types, Server, Client, PubSub,
Configuration, Gds (server + client), Lds, and the Quickstarts/Console
reference apps. Per-component changes follow the same pattern:
1. Add a `private readonly TimeProvider m_timeProvider;` field.
2. Accept a nullable `TimeProvider? timeProvider = null` as the **last**
constructor parameter (new overload; legacy constructor stays for binary
compatibility and delegates with `timeProvider: null`).
3. Initialise the field with `m_timeProvider = timeProvider ??=
TimeProvider.System;`.
4. Replace `new Timer(...)`, `Stopwatch`, `HiResClock.*`,
`DateTime.UtcNow`-based duration math, and `Task.Delay(delay, ct)` in
timing loops with the matching `m_timeProvider` API (`CreateTimer`,
`GetTimestamp` / `GetElapsedTime`, `GetUtcNow().UtcDateTime`,
`Task.Delay(delay, m_timeProvider, ct)`).
5. Wire the provider through DI: `AddOpcUaServerBuilder` /
`AddOpcUaClientBuilder` register `TimeProvider.System` via
`TryAddSingleton<TimeProvider>()` so tests can swap in
`Microsoft.Extensions.Time.Testing.FakeTimeProvider`.
`HiResClock` itself is kept (so the
`ApplicationConfiguration.DisableHiResClock` schema flag still
round-trips), but **every public member** is now `[Obsolete]` with a
single shared message pointing to the new migration-guide section. The
few internal call sites that still need to set/read `HiResClock` are
wrapped with `#pragma warning disable CS0618`.
### Highlights per component
- **Core / Stack** — `Opc.Ua.Core`, `Opc.Ua.Core.Types`, channel
pipeline (`UaSCBinaryClientChannel`, `ChannelToken`,
`UaSCBinaryChannel`), `ApplicationConfiguration`, certificate
validators, `JwksIssuerKeyResolver`, `TimeProviderExtensions` polyfills
(`GetTimestampMilliseconds`, `GetTickCount`,
`CancellationTokenSource(timeout, timeProvider)`, `Task.Delay(delay,
provider, ct)` polyfill for older TFMs).
- **Server** — session lockout, subscription pipeline
(publish/sample/keep-alive/lifetime), `MonitoredItemQueue`, alarm
sampling rate, `IntervalRunner`, server diagnostics, configuration state
machines, hosted services.
- **Client** — `Session`, managed/V2 subscription engines, reconnect
handlers, channel keep-alive, periodic publishing, complex-type
discovery polling.
- **PubSub** — `IntervalRunner` pipeline, message-receive timers,
MQTT/UDP keep-alive, publishers/readers.
- **Gds / Lds** — `LdsServer`, `LinqApplicationsDatabase` expiry
housekeeping, GDS clients (push, pull), `DirectoryCertificateStore`,
`ConnectionStateMachine`, classic subscription engine.
- **Quickstarts / Console samples** — `SampleNodeManager`,
`ReferenceNodeManager`, `AlarmNodeManager`, `BoilerState`,
`MemoryBufferState`, `PublishedValuesWrites`. Samples resolve via
`(Server as ITimeProviderProvider)?.TimeProvider ?? TimeProvider.System`
so existing ctor signatures stay binary-compatible.
- **Tests** — `Opc.Ua.PubSub.Tests` adds `IntervalRunnerTests`; existing
`SubscriptionTests`, `UaPublisherTests`, and `TestDataSystem` move off
`HiResClock`. Added `Microsoft.Extensions.TimeProvider.Testing` package
for `FakeTimeProvider` (project-load warning surfaces on net48/net472
only — runtime is .NET 8+).
### Migration guide
New section [**Time and Timer abstraction
(`TimeProvider`)**](Docs/MigrationGuide.md#time-and-timer-abstraction-timeprovider)
documents:
- The canonical replacement table (`HiResClock.UtcNow` →
`timeProvider.GetUtcNow().UtcDateTime`, `HiResClock.TickCount64` →
`timeProvider.GetTimestamp()`, `new Timer` → `timeProvider.CreateTimer`,
`Task.Delay(delay, ct)` → `Task.Delay(delay, timeProvider, ct)`, …).
- The `TimeProvider? timeProvider = null` + `??=` constructor pattern.
- DI wiring and how to swap in `FakeTimeProvider` in tests.
- Before/after snippets for `HiResClock.TickCount64`,
`HiResClock.UtcNow`, and `new Timer(...)`.
## Related Issues
- Fixes#2458
## Checklist
- [x] 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.
- [x] 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.
- [ ] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
- [ ] I have addressed **all** PR feedback received.
* 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.
* 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
- Add new managed session, wrapping session and providing connection management and failover handling
- Add new Subscription engine that can act as alternative to current engine, but is based on channels with worker tasks
- Add a fluent builder for managed session clients
- Replace NodeCache with LruNodeCache, rename ILruNodeCache and LruNodeCache to INodeCache and NodeCache
- Update migration guide and document new functionality.
Marc Schier