romanettandClaude Opus 5.5
a6cc7c4bc9
## Summary
The event consumer of a notifier (`MonitoredNode2`) evaluated the where
clause and read every select clause of a reported event once **per event
monitored item**, although items with an equal filter and equal session
locales get the same result. With 750 event items on the Server object
this single consumer thread capped event throughput (follow-up to #4837,
item E1 of the event load investigation).
Now each reported event is evaluated **once per distinct filter**:
- The consumer groups the items of an event by a key of their
`EventFilter` (value equality, generated structural
`IsEqual`/`GetHashCode`) and their session's `PreferredLocales`. The key
is cached per item and recreated when the item's filter or the session's
locales change (ModifyMonitoredItems, locale change). A key remembers
the equal key it was matched against, so after the first event a group
compares by reference.
- A per-event `SharedEventEvaluation` holds the where-clause result and
the field values. The first item that needs them evaluates them.
Evaluation is thread-safe, so a later partitioned fan-out (E2) can queue
a group's items on several threads without evaluating again.
- **Per item, unchanged:** duplicate check, permission and
audit-visibility checks, filtered-retain bookkeeping, queue size and
overflow events, and an own `EventFieldList` with its `ClientHandle` and
`Handle`. A trailing filtered-retain event reads its own fields through
`FilteredRetainTarget`. An item whose filter or locales changed after
the event was grouped evaluates the event itself.
- **No public API or wire change, no reflection.** The evaluation is
offered to the virtual `MonitoredItem.QueueEvent` for the duration of
the call (a `[ThreadStatic]` scope keyed by item and target). Derived
items that override `QueueEvent` therefore still see every event, and
they use the shared result only when they pass the same event on to the
base class. Detecting overrides by reflection was rejected because it is
not NativeAOT-safe.
- The shared `Variant[]` is never written after it is created.
`EventQueueHandler.Publish` only touches the `StatusResult` objects
inside it, which were already shared through the event node,
`TransformQueuedEvents` builds new lists, and pooled `EventFieldList`
reuse only reassigns its fields.
## Measurements
`perf/ServerLoadHarness`, `events` with 50 sessions × 15 subscriptions
(750 items on the Server object), publish interval 100 ms, encrypt,
server GC, `TC_QuickJitForLoops=0`/`OSR=0`. Paired A/B in 2 alternating
rounds; each run was repeated if processes outside the harness used more
than 1.5 cores. The base was #4837's tip (27b6ad0d0), whose event code
is what master has now.
| | base | this PR | change |
|---|---|---|---|
| rate 0: generated events/s | 785 (794 / 775) | 1559 (1660 / 1458) |
**+99 %** |
| rate 0: p50 / p99 event→notify ms | 66 / 166 | 64 / 159 | = |
| rate 0: KB allocated per generated event | 272 | 114 | −58 % |
| rate 0: ms server CPU per generated event | 3.08 | 2.01 | −35 % |
| rate 0: µs CPU / bytes per notification | 4.1 / 366 | 2.7 / 153 | −34
% / −58 % |
| rate 500: ms server CPU per generated event | 3.15 | 2.63 | −16 % |
| rate 500: KB allocated per generated event | 297 | 154 | −48 % |
| rate 500: p50 / p99 event→notify ms | 74.7 / 144.7 | 71.6 / 137.8 | =
(bound by the publish interval) |
CPU traces (`threads`): before, one consumer thread was 99.5 % busy,
mostly in the field read chain (`GetAttributeValue` 23.5 %,
`ReadValueAttribute` 12.5 %) plus `QueueEvent` (19 %). After, the
consumer still uses about one core, now ~87 % in per-item queueing
(`EventMonitoredItemQueue` list copies). The per-item `Variant[]`, which
was 45 % of the sampled allocated bytes, is gone. **The post-E1
single-thread cap is ~1,500–1,660 generated events/s**, the reference
for a partitioned parallel fan-out (E2).
## Tests
- New `SharedEventEvaluationTests`:
- Mixed select clauses, where clauses and session locales on one
notifier (Server node with multiple consumers and a regular node) each
get exactly what per-item evaluation gives.
- A counting `IFilterTarget` proves that 20 items with an equal filter
read the event once.
- A derived item that overrides `QueueEvent` sees every event.
- A session locale change takes effect with the next event.
-
`FilterRetainTests.FilteredRetainStaysPerItemWhenItemsShareTheEvaluationAsync`:
only the item that saw the condition in scope gets the trailing `Retain
= false` event.
- Test runs:
- `Opc.Ua.Server.Tests` (net10.0): all pass except
`BindingLivenessRacingTransfersAndCloseNeverConfirmsReplacedBindingAsync`,
a session-binding race that is unrelated and passes 3/3 when run alone.
After rebasing onto master, the event, condition, alarm, filter and
monitored-item subset ran 1619 of 1620 passing;
`WriteAsync_PublishesValueToMonitoredItemQueueAsync` (a data-change
write test) failed once in the parallel run and passed 9/9 alone.
- Explicit `ServerEventSubscribeLoadTestAsync`: passes over opc.tcp. The
https/opc.https fixtures fail with HTTP 503 on master too.
- Builds clean for net48.
🤖 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.