OPCFoundation.NetStandard.Opc.Ua.Redundancy.Server

OPC UA .NET Standard — Distributed / High-Availability Server

OPCFoundation.NetStandard.Opc.Ua.Redundancy.Server adds the optional distributed building blocks that let an OPCFoundation.NetStandard.Opc.Ua.Server server run as a redundant replica set (active/passive or active/active) while sharing its address space and — optionally — its session state across replicas.

Overview

The core server library stays a self-contained, single-instance server. This package layers the distributed concerns on top through dependency injection so the in-memory, single-instance path is unchanged when the package is not used:

• A shared, integrity-protected key/value backend (ISharedKeyValueStore) that mirrors node additions, removals, references, and values across replicas.
• Leader election (ILeaderElection) for the shared-read / leader-write redundancy model, surfaced to clients through the standard OPC UA ServiceLevel and redundancy nodes.
• Opt-in mirrors for HotAndMirrored/Transparent failover: encrypted session state with single-use nonce validation, subscription definitions, retransmission queues for Republish, best-effort continuation-point envelopes, and deterministic EventIds when an IEventIdProvider such as DeterministicEventIdProvider is configured.

Getting started

Wire the distributed address space and (optionally) shared sessions through the fluent DI surface:

services.AddOpcUa()
    .AddServer(...)
    .UseDistributedAddressSpace(distributed =>
    {
        distributed.UseSharedKeyValueStore(new InMemorySharedKeyValueStore());
    })
    .UseDistributedSessions();

The single-instance defaults remain in effect until a shared store is supplied, so the same server binary runs stand-alone or as part of a replica set.

Target frameworks

net472, net48, netstandard2.1, net8.0, net9.0, net10.0.

Additional documentation

See the High Availability guide for the OPC UA redundancy mapping and the Kubernetes deployment guide for running the server as a replica set.