Wolfgang ColsmanandMarc Schier
be9ccf912c
# Description
## Problem
`ISubscription.SetAsDurableAsync(TimeSpan lifetime, CancellationToken
ct)` marks a subscription durable with the Server method
`SetSubscriptionDurable` (OPC 10000-5, "SetSubscriptionDurable Method";
OPC 10000-4, "Durable Subscriptions"). `SetSubscriptionDurable` must be
called before the subscription has monitored items; a conforming server
rejects it afterwards with `Bad_InvalidState`.
`LogicalSubscription` stores the `TimeSpan` and installs an
`OnAfterCreateAsync` hook on each partition. The partition state machine
runs the hook after every `CreateSubscription` and before the first
`CreateMonitoredItems`, so durability survives every later physical
create:
- recreate after a service call reports `BadSubscriptionIdInvalid`
(`Subscription.ApplyStateChangesAsync` → `ResetToRecreateAsync`),
- recreate after `TransferSubscriptions` fails on session recreate
(`SubscriptionManager.RecreateSubscriptionsAsync` → `RecreateAsync`) or
on load (`RestoreTransferAsync` → `ResetToRecreateAsync`),
- recreate after a status-change timeout or an unsolicited
`Good_SubscriptionTransferred`,
- a new secondary partition (`TryApplyDurableToNewPartition`).
The hook always re-applies the lifetime fixed by the first call. An
application whose durable lifetime must not exceed a bound that shrinks
over time (for example an authorization or retention window that ends at
a known instant, after which the server must no longer queue
notifications) cannot keep that bound after a recreate, and it has no
way to supply a new value at the right moment:
- calling `SetAsDurableAsync` again after the recreate is rejected once
monitored items exist;
- `ISubscriptionNotificationHandler.OnSubscriptionStateChangedAsync` is
dispatched fire-and-forget, so a call made from it can arrive after the
first `CreateMonitoredItems`;
- `SubscriptionOptions` has no durable setting and `OnAfterCreateAsync`
is internal.
## API
```csharp
namespace Opc.Ua.Client.Subscriptions
{
public interface ISubscription
{
// existing
ValueTask<TimeSpan> SetAsDurableAsync(TimeSpan lifetime, CancellationToken ct = default);
// new
ValueTask<TimeSpan> SetAsDurableAsync(Func<TimeSpan?> lifetime, CancellationToken ct = default);
}
}
```
## Behaviour
- The provider is evaluated once for the call itself; the value is sent
to every partition that is already created (unchanged: the call returns
the minimum revised lifetime of those partitions, or the requested value
when none is created yet).
- The provider is stored and evaluated again by the existing
after-create hook before every later physical create, between
`CreateSubscription` and the first `CreateMonitoredItems` of that
create.
- A `null` result requests no durability for that create: no
`SetSubscriptionDurable` is sent and the recreated subscription is a
regular one. A `null` result for the call itself returns `TimeSpan.Zero`
without contacting the server.
- An exception thrown by the provider during a later create is handled
exactly like a rejected `SetSubscriptionDurable` call today: the state
machine logs a warning, reports `SubscriptionState.Modified`, and the
subscription continues (its monitored items are created). An exception
during the call itself propagates to the caller.
- `SetAsDurableAsync(TimeSpan)` now forwards to `SetAsDurableAsync(() =>
lifetime)`; its behaviour is unchanged.
- `docs/Subscriptions.md` describes the provider and corrects the
statement that the hook is cleared after invocation (on master it stays
installed).
Not included: a notification reporting the outcome (revised lifetime or
status) of each re-applied `SetSubscriptionDurable`. Today a failed
re-apply is only logged and surfaced as `SubscriptionState.Modified`;
this could be a follow-up if maintainers want it.
## Tests
New tests in
`tests/Opc.Ua.Client.Tests/Subscription/SubscriptionTests.DurableLifetime.cs`
drive a real partition (`Subscription`) behind
`SubscriptionManager`/`LogicalSubscription` against mocked services and
record `CreateSubscription`, `SetSubscriptionDurable` (requested hours),
`CreateMonitoredItems`, `TransferSubscriptions` and
`DeleteSubscriptions` in call order. The provider returns 10 h for the
initial call and 7 h afterwards:
-
`DurableLifetimeProviderIsEvaluatedOnRecreateAfterSubscriptionIdInvalidAsync`:
`ModifySubscription` returns `BadSubscriptionIdInvalid`; the recreate
sends 7 h between `CreateSubscription` and the first
`CreateMonitoredItems`.
-
`DurableLifetimeProviderIsEvaluatedOnRecreateAfterFailedTransferAsync`:
`TransferSubscriptions` on session recreate returns
`BadSubscriptionIdInvalid`; delete, create, 7 h, items.
- `DurableLifetimeProviderIsEvaluatedForNewPartitionAsync`:
`MaxMonitoredItemsPerPartition = 1`; the second item mints a partition
that sends 7 h before its items.
-
`DurableLifetimeProviderReturningNullSendsNoSetSubscriptionDurableAsync`:
provider returns `null` on recreate; no `SetSubscriptionDurable`, items
are created.
-
`DurableLifetimeProviderThatThrowsLeavesRecreatedSubscriptionRunningAsync`:
provider throws on recreate; no `SetSubscriptionDurable`, items are
created, subscription stays created.
- `DurableFixedLifetimeIsReappliedOnRecreateAsync`: regression of the
`TimeSpan` overload (10 h again on recreate).
Unit tests in `LogicalSubscriptionTests`:
`SetAsDurableWithProviderEvaluatesItOnceForAllCreatedPartitionsAsync`,
`SetAsDurableWithProviderReturningNullSendsNothingAsync`,
`SetAsDurableWithNullProviderThrowsAsync`.
Negative control: with the hook evaluating the provider once at
installation (the previous fixed-value behaviour), the
recreate-after-`BadSubscriptionIdInvalid`, failed-transfer, null and
throwing-provider tests fail (4 of 10).
Local results (Windows, .NET SDK 10.0.402, Release):
| Run | Result |
| --- | --- |
| `Opc.Ua.Client` build, net48/net8.0/net9.0/net10.0 | 0 warnings, 0
errors |
| `SubscriptionTests` + `LogicalSubscriptionTests`, net10.0 | 105/105
passed |
| `SubscriptionTests` + `LogicalSubscriptionTests`, net48 | 105/105
passed |
| `Opc.Ua.Client.Tests`, namespace `Opc.Ua.Client.Subscriptions`,
net10.0 | 353/353 passed |
| `Opc.Ua.Subscriptions.Tests` `SubscriptionManagerCoverageTests` +
`StreamingSubscriptionCoverageTests`, net10.0 | 72/72 passed |
| `Opc.Ua.Subscriptions.Durable.Tests` `SubscriptionDurableTests` +
`DurableSubscriptionTest*` (in-process reference server with durable
subscriptions enabled), net10.0 | 21/21 passed |
## Related observation (not changed here)
A secondary partition minted by `SubscriptionManager.Add`'s partition
factory starts its state machine in the `Subscription` constructor,
before the factory calls `TryApplyDurableToNewPartition`. When
`CreateSubscription` completes before the factory returns (observed with
a synchronously completing mock), `RunAfterCreateHookAsync` finds no
hook and the new partition is created without `SetSubscriptionDurable`,
for the `TimeSpan` overload as well. With a real round trip the hook is
installed first;
`DurableLifetimeProviderIsEvaluatedForNewPartitionAsync` therefore holds
the secondary's `CreateSubscription` response until the factory has
returned. Installing the hook before the partition's first state-manager
pass would remove the window.
## Compatibility
- Source and binary compatible for callers of `ISubscription`.
- `ISubscription` gains a member. Custom implementations of the public
interface (outside the stack; the stack's own implementations are
internal) must add the overload; a default interface implementation is
not possible because the library also targets .NET Framework 4.8. The
three test doubles in the repository were updated.
- No wire, configuration or server change.
## Related Issues
- Independent of #4881; with #4881 the lifetime provider is also applied
to a new partition that is created before the partition factory returns.
## 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. (Run
locally: the affected test classes on net48 and net10.0 and the whole
Opc.Ua.Client.Tests project on net10.0; not the whole UA.slnx.)
- [ ] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
- [ ] I have addressed **all** PR feedback received.
---------
Co-authored-by: Marc Schier <marcschier@users.noreply.github.com>
OPC UA .NET Standard Stack
🆕 This is version 2.0 of the OPC UA .NET Standard Stack (current
master).Looking for the supported 1.x release? It lives on the
master378branch (last release:1.5.378). All new feature work happens here onmaster;master378continues to receive security and critical-bug fixes for the 1.x line.
The official OPC Foundation reference implementation of OPC UA for .NET — a cross-platform stack with client, server, PubSub, GDS, complex types, and source-generated tooling. Used in production across industrial control, manufacturing, energy, and IoT systems.
📦 What it is
- A full-stack OPC UA implementation — Core / Client / Server / PubSub / GDS / LDS / Complex Types / Device Integration / Positioning libraries built on .NET, with UA-TCP and HTTPS transports.
- Cross-platform — runs on .NET 10, .NET 9, .NET 8 (LTS), .NET Framework 4.8; ships Native-AOT-friendly assemblies.
- Conformance regression testing — the reference server is tested with the Compliance Test Tool (CTT) through the CTT regression workflow. These results identify regressions; they do not constitute product certification.
- Companion-spec coverage — Part 9 (Alarms & Conditions), Part 10 (Programs), Part 11 (Historical Access), Part 13 (Aggregates), Part 16 (State Machines), Part 17 (Alias Names), Part 18 (Role Management), Part 20 (File Transfer), Part 100 (Device Integration), Part 110 (Asset Management Basics), Parts 210/211 (Relative Spatial Location and Global Positioning), OPC-10030 (ISA-95 Common Model) with OPC-10031-4 Job Control V1/V2, OPC 30270 / OPC UA for Asset Administration Shell V2 and V3, OPC 10100-1 (WoT Connectivity), Part 200 (Industrial Automation), OPC 40001-1/-2/-3/-4/-101 (Machinery with Process Values, Job Management, Energy and Result Transfer), OPC 34100 (Energy Consumption Management), OPC 30081 (PA-DIM), OPC 40010-1 (Robotics), OPC 40100-1/-2 (Machine Vision control and asset management), OPC 40501-1 and OPC 40505 (Machine Tools and independent wireless peripherals), OPC 40210 (Geometric Measurement Systems, with its documented upstream Production-facet exception), OPC 40020-1 (Cranes and Hoists), OPC 40223 (Pumps and Vacuum Pumps), OPC 30010 (AutoID Devices), OPC 40200 (Weighing Technology) with OPC 30050 (PackML).
- Hosting and code generation —
Microsoft.Extensions.DependencyInjectionhosting (services.AddOpcUa()), fluent server + client builders, source-generated NodeManagers and DataTypes, and an MCP server so LLMs / Copilot can drive an OPC UA client.
For the full feature breakdown see OPC UA Profiles and Facets and the What's New in 2.0 tour.
🚀 Getting started
To run a first OPC UA client and server, from NuGet packages or from the samples in this repository, follow Getting started. The documentation index then leads from the core concepts to advanced and experimental features.
The recycling operator console demonstrates live browser monitoring, native companion-specification inspection, material genealogy, and authorized controls over the synthetic recycling line.
You need a stable .NET SDK
version 10.0.400 or later to build the repo. global.json selects the
highest installed stable SDK, including newer major versions. From the repository root:
dotnet restore UA.slnx
dotnet build UA.slnx
For the supported target frameworks and platform notes see
the Developer Guide. The official NuGet packages
are published to nuget.org under the OPCFoundation.NetStandard
prefix — the meta package
OPCFoundation.NetStandard.Opc.Ua
bundles a default set of stack packages; see its
package inventory.
Reference PubSub and other optional feature packages separately, or select
individual packages directly, e.g.
OPCFoundation.NetStandard.Opc.Ua.Client for clients or
OPCFoundation.NetStandard.Opc.Ua.Server for servers. Preview builds from
every successful master build are available from the
GitHub Packages NuGet feed,
which is the only feed they are published to. nuget.org receives a version
only through a manually approved promotion from a release/<major>.<minor>
branch — that is where the 2.0.0-preview.N packages already on nuget.org
came from, via the earlier release/2.0.0 line. To use those, enable
prerelease packages and float with 2.0.0-preview.* until 2.0.0 is
released. The XRegistry, WoT Connectivity, Robotics, CranesHoists,
Redundancy, Positioning, OpenUSD, and AI package families, the Vision.OpenUsd
renderer, and the Robotics MCP extension remain
preview packages when the root version is promoted to a stable version, and
keep their own -preview.N versions on nuget.org. This includes all CranesHoists
model/server/client/MCP packages and their Debug variants.
The Vision, MachineVision, MachineTool (including WMTP), and GMS
model/client/server packages and their MCP packages follow the root version
without a preview-only override;
development builds still inherit the root prerelease version. See
docs/ReleaseProcess.md for how and when stable
versions are released.
Samples
The platform-independent sample applications show how to use the stack's core services and companion models in client/server workflows. More applications, including platform-specific examples, are available in the companion OPC UA .NET Samples repository.
Developer tools
- UaLens — NativeAOT-capable desktop engineering workspace for secure connections, monitoring, alarms, structured values, history, administration, PubSub, continuity diagnostics, and guided companion-model tasks. See build and artifact qualification.
- OPC UA MCP Server — installable .NET tool and container exposing OPC UA client operations to LLMs and Copilot. Embeddable libraries provide Part 4 services, PubSub, diagnostics, Robotics and Vision, plus industrial companion profiles for AMB, Machinery, Scales, Pumps, AutoID, Device Integration, ISA-95 and Positioning. The WoT and xRegistry profiles add asset/registry management and bounded document validation, planning and NodeSet conversion. Stack workflow profiles provide GDS/credential issuance, roles/users, files, alarms, history, schemas, and host-authorized PubSub and live WoT execution.
🔧 Migrating from 1.5.378 to 2.0
The 2.0 release introduces breaking API changes, and comes with a full prescriptive migration guide that links to per-area documentation for the migration sub-topics.
Most of the mechanical migration work is automated:
OPCFoundation.NetStandard.Opc.Ua.MigrationAnalyzerNuGet — install it in your project to get 26 analyzer rules throughUA0030(excludingUA0013,UA0016,UA0017, and the shim-onlyUA0029) plus one-click code fixes for the patterns in the guide. Setup steps are in the package's NugetREADME.md.- Migration agent skill — the
opcua-v20-migrationskill walks Copilot / Claude / any coding agent through installing the NuGet, runningdotnet format analyzersto apply auto-fixes, and handling the remaining manual changes. It selects the migration sub-document for each symptom.
Copilot CLI discovers the skill automatically inside a clone. To install it for use in any repository:
copilot plugin marketplace add OPCFoundation/UA-.NETStandard
copilot plugin install opcua-v20-migration@opcua-dotnet
If you are still on 1.x and not ready to upgrade, stay on the
master378
branch — it continues to receive security and critical-bug fixes.
🤝 Contributing and license
Community contributions are welcome. Fork the repository, make your changes on a branch, and open a pull request; see CONTRIBUTING.md for the contribution workflow.
Contributors must sign the OPC Foundation Contributor License Agreement (CLA). The CLA "I AGREE" gate is presented automatically on your first PR.
The project is licensed under the OPC Foundation MIT License. Report security vulnerabilities via the process documented in SECURITY.md.
📚 Further reading
- Documentation index — every per-feature doc with a one-line description.
- What's New in 2.0 — narrative tour of the 1.5.378 → 2.0 changes grouped by theme and layer.
- OPC UA Profiles and Facets — facets / transports / security policies the stack implements.
- Migration Guide — prescriptive
per-version migration reference (links to
docs/migrate/2.0.x/). - OPC UA Online Reference — the official OPC 10000 series specification index.
- Preview Nuget package feed —
prerelease builds from every successful
masterbuild.