# Description
Introduces a central `IClientChannelManager` that owns client-side
transport channels with reference counting, sharing, coalesced
reconnect, and asynchronous participant notification. Sessions,
discovery clients, and registration clients targeting the same
`ConfiguredEndpoint` (with the same reverse-connect identity) now share
a single underlying `ITransportChannel`; reconnect is transparent to
callers; and the previous `AttachChannel`/`DetachChannel` +
`SessionReconnectHandler` patterns are obsoleted.
## What lands
### Core types (`Stack/Opc.Ua.Core/Stack/Client/`)
- `ManagedChannelKey`, `ChannelState`, `ChannelStateChange`,
`ParticipantReconnectResult`
- `IReconnectParticipant`, `IManagedTransportChannel`,
`IClientChannelManager`
- `IChannelReconnectPolicy` + `ExponentialBackoffChannelReconnectPolicy`
(default mirrors historical `SessionReconnectHandler`: 500 ms → 30 s
exponential)
- `IRetryBudget` + `RetryBudget` — shared retry deadline so the
two-level retry no longer compounds multiplicatively
- `ClientChannelManager` — single non-partial sealed class with
SOLID-extracted internal types under
`Stack/Opc.Ua.Core/Stack/Client/Channels/Internal/`: `ChannelEntry`
(behind `IChannelEntryHost`), `ManagedTransportChannelLease`,
`ClientChannel`, `ClientChannelManagerMetrics` (IMeter),
`ClientChannelManagerCertRotation` (auto `ReconnectAllAsync` on
`CertificateManager` rotation), `ClientChannelManagerDiagnostics`
(ActivitySource + EventSource). Refcount, coalesced reconnect, and
transparent faulted-entry recovery via `SwapFaultedEntryAsync` (swaps a
lease's underlying entry on subsequent `ReconnectAsync` when the prior
cycle Faulted/Closed, preserves participant, back-off via policy
`GetDelay(SwapCount)`)
### Three-state lifecycle gate
`Disconnected` → `TransportConnecting` / `TransportReconnecting` →
`TransportConnectedSessionReactivating` → `Ready` (or `Faulted` /
`Closed`). Only `Ready` releases the service-call gate; the manager
bypasses the gate internally for participant `ActivateSession` traffic
during reactivation via an `AsyncLocal` scope.
### Session integration (`Libraries/Opc.Ua.Client/Session/`)
- New `Session.CreateAsync(IClientChannelManager, …)` overload
- `Session` implements `IReconnectParticipant`; reactivation handler
distinguishes `Reactivated` / `RequiresSessionRecreate` /
`TransientFailure` / `FatalForParticipant` / `FatalForChannel`
- `Session.ReconnectAsync(ct)` automatically delegates to the channel
manager when wired
- `Session.RecreateInPlaceAsync` swaps managed-channel leases for
failover-to-different-endpoint via a new atomic
`IClientChannelManager.GetAsync(endpoint, participantFactory, …)`
overload; same-key recreates delegate to manager reconnect;
explicit-channel/connection callers retain legacy behavior
- KA failure routes through
`IClientChannelManager.ReconnectAsync(channel)`
### ManagedSession integration
- `WithChannelManager(...)` builder + ctor param; DI-resolved
automatically
- Two-level retry: channel-mgr handles transparent reconnect; outer
`ConnectionStateMachine` + `IReconnectPolicy` only triggers on terminal
channel `Faulted`. Outer-state churn suppressed during channel-mgr
cycles via `_channelReconnectInProgress` flag wired through
`IManagedTransportChannel.StateChanged`
- New `ManagedSession.ChannelStateChanged` event surfaces transparent
reconnects
- `ConnectionStateChangedEventArgs.UnderlyingChannelState` populated
when outer reconnect was triggered by a channel fault
- Shared `IRetryBudget` propagated so the layers enforce a single
max-total-time
### Discovery / Registration / GDS
Channel-manager-aware `CreateAsync` overloads on `DiscoveryClient`,
`RegistrationClient`, `ServerPushConfigurationClient`,
`LocalDiscoveryServerClient`, `GlobalDiscoveryServerClient`. Each
registers a minimal `IReconnectParticipant`; co-located sessions and
discovery probes targeting the same endpoint share a channel.
### HTTPS transport (`Stack/Opc.Ua.Bindings.Https/`)
- New `IOpcUaHttpClientFactory` abstraction
- HTTPS / OPC-HTTPS channels migrated to `IHttpClientFactory` +
`Microsoft.Extensions.Http.Resilience` (10.6.0; AOT-compatible on net10
via source generators; legacy direct-HTTP path retained for older TFMs /
no-DI consumers)
### DI
`AddOpcUa().AddClient(...)` registers `IClientChannelManager` and the
named HTTPS `HttpClient` + standard resilience handler automatically.
`ManagedSessionBuilder` resolves the manager from DI when present.
### Obsoletions (functional, `[Obsolete]` with guidance)
- `IClientBase.AttachChannel` / `DetachChannel`
- `SessionReconnectHandler`
- `SessionExtensions.ReconnectAsync(connection, ct)` and `(channel, ct)`
legacy overloads
### Tests
- Core: `ClientChannelManagerManagedTests`,
`ClientChannelManagerCertRotationTests`, `RetryBudgetTests`,
`OpcUaHttpClientFactoryTests` — **56 / 56 pass**
- Client: `ManagedSession*Tests` updated; legacy
`SessionReconnectHandlerTests` + `SessionExtensionsTests` preserved with
`#pragma warning disable CS0618` — **129 / 129 pass**
- Sessions integration: `ChannelManagerSharing` / `TransparentReconnect`
/ `SessionLifecycle` / `CertRotation` — **7 pass, 1 skipped**
(`ChannelManagerExhaustionEscalatesAndRecoversWhenServerReturns`
un-`[Ignore]`d and implemented in this PR via `SwapFaultedEntryAsync`;
remaining skip is end-to-end `RequiresSessionRecreate` plumbing —
carry-forward)
- Stress (consolidated `Tests/Opc.Ua.Stress.Tests/Subscriptions/` +
`Channels/`): chaos / contract / soak / lifecycle / leak-accuracy / gap
/ participant-result-aggregation tests merged from the
previously-separate `Opc.Ua.Channels.Stress.Tests` project; nightly run
via `.github/workflows/stress-test.yml`
Builds clean (0 warnings / 0 errors) across all six TFMs: `net472`,
`net48`, `netstandard2.1`, `net8.0`, `net9.0`, `net10.0`.
### Docs
- `Docs/Sessions.md` new § 4 documents the channel manager, three-state
gating, two-level retry with shared `IRetryBudget`, HTTPS resilience
layering
- `Docs/MigrationGuide.md` migration recipes for the four obsoleted API
groups
- `Docs/DependencyInjection.md` channel-manager and HTTPS factory
registration
## Carry-forward (separate PRs)
- End-to-end `ParticipantReconnectResult.RequiresSessionRecreate` →
`Session.RecreateAsync` lifecycle wiring (currently incomplete — flagged
in the 1 remaining skipped integration test)
## Related Issues
- Fixes#3288
- Builds on #3282 (PR that introduced the initial
`ITransportChannelManager` skeleton)
## 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.
*(Channel-manager-specific tests + ManagedSession/client tests verified
across all 6 TFMs; full UA.slnx run is pending CI.)*
- [ ] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
- [ ] I have addressed **all** PR feedback received.
* 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 interop test agent
The new stack-pass ObjectMethodProxyGenerator emits proxies that derive
from Opc.Ua.ObjectTypeClient and reference Session.MessageContext.NamespaceUris.
Neither type exists in the in-memory test compilation, which only references
Opc.Ua.Types.dll. Moving ObjectTypeClient to Opc.Ua.Types would cascade ISessionClient,
IClientBase, ITransportChannel and the generated service interfaces with it, so the
type stays in Opc.Ua.Core and we add a minimal stub to OpcUaCoreStubs instead.
Wire Microsoft.Extensions.Options 10.0.5 + DependencyInjection.Abstractions 10.0.5 into Directory.Packages.props and the Gds.Client.Common project to enable upcoming options-driven configuration work.
Modernize Opc.Ua.Gds.Client.Common (DI, options, interfaces, async dispose)
This pull request modernizes the OPC UA .NET codebase and tests, removes .NET Standard 2.0 support from certificate/security code, and updates test code to use C# 12 and .NET 8+ features for clarity and maintainability.
- Certificate and BouncyCastle interop files (e.g., CertificateBuilder.cs, X509Extensions.cs, X509SignatureFactory.cs) are refactored to drop NETSTANDARD2_0 support and use modern .NET APIs and conditional compilation.
- Test code across the codebase is updated to use default, strongly-typed Parse methods, collection expressions, and improved async/await patterns.
- Exception handling and assertions in tests are modernized, and test method naming is made consistent with Async suffixes.
- The project and build files are updated to clarify Roslynator analyzer usage and remove obsolete netstandard tags.
- General code and test cleanup includes improved null safety, type safety, and removal of deprecated or unused code.
* Refactor for robustness and async improvements
Refactored code to enhance robustness and maintainability by enabling nullable reference types and using `async`/`await` for asynchronous operations. Updated exception handling to use `BadNotConnected()` for more accurate error states. Removed unused code and improved test files to align with these changes. Introduced `OpenInternalAsync` for better channel management and handled on-demand connection creation in `SendRequestAsync`.
* Obsolete APM
* Remove WCF remainders, channel clean up and initial cut at Channel factory
* Clean up copyright notice formatting
* Make connect async in Socket and abstract bindings for easier testing
* Fix unit tests
These changes enhance robustness, maintainability, and correctness of channel and task management.
---------
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Roman Ettlinger <romanett98@gmail.com>
- Allow setting ReturnDiagnostics on the session factory to ensure the diagnostic settings are part of "Create" also. Set them to SymbolicIdAndText by default.
- Better logging in unit tests, now also logs to progress including exception traces, also prefixes SERVER and TEST on console to attach the logs to the server or client side.
- GDS client stability improvements to ensure client reliably reconnects between calls when connection is lost.
- Do not dispose the application certificate when it is updated from GDS client to avoid existing sessions to crash with CryptographicException. This needs more improvements later on because it is rather hacky today.
- Remove the certificate cache in CertificateFactory (as per discussion and agreement) which allowed re-enabling the older UserIdentity API
- Logging improvements here and there to analyze issues in unit tests better
Marc Schier