70e9873328
Q4 and Q5 of the request-queue comparison with ASP.NET Core/Kestrel (Q1 is #4914). Two commits, one per item. ## Q4: stop changing the process ThreadPool `RequestQueue` called `ThreadPool.SetMinThreads` / `SetMaxThreads` for the whole process every time a queue was created, including a throwaway 10-worker queue that the `ServerBase` constructor built and `InitializeRequestQueue` disposed again at start. - The calls are removed. Nothing in the repo (src, tests, samples) depends on them. Queue workers are asynchronous and do not hold a pool thread while they wait. `SetMaxThreads` never had an effect, because the default maximum (32767) is always above the configured counts. - The constructor no longer builds the throwaway queue. Until the server starts, `ServerBase.ScheduleIncomingRequest` completes a request with `BadServerHalted`. That request used to reach `ProcessRequestAsync` of a server that had not started yet. ### Release note (behaviour change) > The server no longer raises the process-wide thread pool minimum to `MinRequestThreadCount` (default 10). On machines with fewer logical processors than `MinRequestThreadCount`, the thread pool now starts with its own default minimum (the processor count). Hosts whose node managers block threads synchronously, and that relied on the old minimum, can set it themselves with `ThreadPool.SetMinThreads` or the `System.Threading.ThreadPool.MinThreads` runtime setting. ### Test hosts CI showed that test hosts depended on the old minimum. On the small linux runners, tests that block pool threads in parallel left a queued request waiting more than 5 s for a thread (`RequestQueueTests`, `RequestLifetimeTests`). `tests/TestThreadPoolSetup.cs` is an assembly-wide NUnit `SetUpFixture` that `tests/Directory.Build.targets` compiles into every NUnit test project. It restores the minimum of at least 10 worker and I/O threads, for the test hosts only. ## Q5: request queue metrics The SharedOnly path only logged `RequestQueueFull` (with a `// TODO: make a metric`). The queue now publishes instruments in both the shared and the isolation mode. They follow the style of `DefaultServerResourceIsolationProvider` and are modelled on Kestrel's `kestrel.queued_requests`, `http.server.active_requests` and `aspnetcore.rate_limiting.request.time_in_queue`. The meter comes from the server's `ITelemetryContext` (`CreateMeter()`, named after `Opc.Ua.Core`) and is disposed once shutdown has drained the queue. | Instrument | Type | |---|---| | `opcua.server.request_queue.queued` | observable gauge | | `opcua.server.request_queue.executing` | observable gauge | | `opcua.server.request_queue.parked` | observable gauge | | `opcua.server.request_queue.time_in_queue` | histogram, seconds | | `opcua.server.request_queue.rejections` | counter, tag `status` | Cost on the request path: - The gauges are observed from counters that already exist, so they add no work per request. - The time in queue uses a `Stopwatch` timestamp taken at enqueue, and only while the histogram has a listener, on both paths. The fair queue stamps an `Entry` only after its admission succeeds. Once the Q2 enqueue/received timestamp lands, it can replace this one. - Rejections are tagged with the interned symbolic id of the status code through the single-tag `Add` overload, so no tag array is allocated. - Rejections include queue full, halted, cancelled while queued, failed revalidation and every fair-admission rejection, because the fair queue's completion callback now goes through `RejectRequest`. Handler failures are not rejections. `docs/ServerScalability.md` lists the instruments. ## Tests - `RequestQueueTests`: request before start is halted, ThreadPool limits unchanged, shared queue metrics (queued, executing, parked, rejections by status, time in queue), parked gauge, fair queue metrics. - `Opc.Ua.Core.Tests` `Stack.Server`: 1946 passed, 0 failed (net10.0). - `Opc.Ua.Server.Tests`: 9653 passed. The 8 failures are symlink tests (`FileLinksRejectReadWriteAndCopy` and similar) that fail on this machine with "insufficient privileges" and are unrelated to this change. - net48 build of `Opc.Ua.Core.Tests` compiles. Conflicts to expect: the Q2/Q3 session (time in queue against TimeoutHint, retry-after) touches the dequeue and reject spots of `ServerBase.RequestQueue.cs`. 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com> Co-authored-by: Marc Schier <marcschier@users.noreply.github.com> Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: marcschier <11168470+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.