romanettandClaude Opus 5.5
5f6faa60d7
Removes per-request allocations on the server's single-value Read path
with small, internal changes. No wire-format change, no public API
change, no change of the execution model (the receive loop is
untouched). Exactly-once semantics of the isolation leases,
cancellation, timeouts, diagnostics and auditing are unchanged.
## Effect
Allocated bytes per single-value Read (perf harness, `native-read`, 10
clients x 100 in flight, `AsyncCustomNodeManager`, Server GC;
deterministic):
| | 1 core | 4 cores |
|---|---|---|
| master 4ae2395f3 | 2929 | 2753 |
| this PR | 2320 (-21 %) | 2326 (-16 %) |
Per commit (4 cores): T1 -120 B, T2 -64 B, receive chunk list ~-70 B,
closure -17 B, pool floor -74 B, routing capture ~-100 B.
CPU per request is unchanged within the noise of a shared machine
(paired, alternating A/B rounds, 4 pinned cores: async node manager -1.8
%, encrypted -4.7 %, sync node manager +2.5 %, all ranges overlapping).
Read with 1/100 nodes and 20/200 sessions, Browse and subscriptions show
no regression and 1-14 % fewer bytes.
## Changes (one commit each)
1. **Isolation stages held as reservations.** `FairRequestQueue`
acquired three to four `Lease` objects per request. The default provider
now also admits by value through an internal
`IResourceIsolationReservations`; the queue entry keeps one compact hold
per stage and releases it exactly once with an atomic exchange. Other
providers keep using leases. `TryAcquire` and its lease are unchanged.
2. **Validation scopes reused.** Disposed `RequestValidationScope`s are
kept in per-processor spare slots and reused under a new id. Ids stay
unique, so a drain that read a scope before its reuse can only wait for
the newer validation, never miss one.
3. **Receive chunk list reused.** The server channel keeps the
`BufferCollection` of a dispatched request (released after the handler;
the decoder copied the request) to assemble the next single-chunk
message.
4. **No closure per service call.** The rejection counter lambda in the
catch block of 28 service methods made the async method allocate its
closure on every call. It moved into `CountRejectedServiceRequest`.
5. **Pool floor.** The request continuation and response source pools
retained 4 objects per processor; with many requests in flight, bursts
of completions overflowed them. They now retain at least 256.
6. **Routing snapshot captured without a restore.** #4759 captures the
routing snapshot per service call in an `AsyncLocal` through a
`ReadScope`; the capture, the scope object and the restore on dispose
cost about 190 B per Read. The dispatcher's service methods capture
until they return, and an async method's execution-context changes end
when it returns, so these sites use the new internal
`CaptureUntilReturn` (no scope, no restore, no write when already
captured). Captures that end inside a method keep the scope. The capture
itself (~90 B) remains.
Not included: pooling `FairRequestQueue.Entry` (an entry is also the
node of the lock-free FIFO and stays referenced after dispatch) and
caching a `NodeHandle` per node (the shared, publicly mutable handle
would reach overridable node manager code).
## Tests
- New: queue tests run against a reservation-capable provider and assert
every stage is released exactly once (a deliberately broken release
fails 6 of them); validation scope reuse with drains; routing capture
ends when the async method returns (sync and async completion).
- Locally on net10.0: Opc.Ua.Core.Tests, Opc.Ua.Server.Tests,
Opc.Ua.Client.Tests, Opc.Ua.Sessions.Tests and Opc.Ua.Stress.Tests
(Contract, Integration) pass; net48 test projects compile.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.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 certified, 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.
- Certified for compliance — the reference server has been certified through an OPC Foundation Certification Test Lab and is continuously verified against the latest Compliance Test Tool (CTT).
- 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 the .NET 10 SDK to build the repo. 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
pulls in everything, or reference 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
- 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.