Phase 3 PR 68 -- OPC UA Client ITagDiscovery via recursive browse (Full strategy). Adds ITagDiscovery to OpcUaClientDriver. DiscoverAsync opens a single Remote folder on the IAddressSpaceBuilder and recursively browses from the configured root (default: ObjectsFolder i=85; override via OpcUaClientDriverOptions.BrowseRoot for scoped discovery). Browse uses non-obsolete Session.BrowseAsync(RequestHeader, ViewDescription, uint maxReferences, BrowseDescriptionCollection, ct) with HierarchicalReferences forward, subtypes included, NodeClassMask Object+Variable, ResultMask pulling BrowseName + DisplayName + NodeClass + TypeDefinition. Objects become sub-folders via builder.Folder; Variables become builder.Variable entries with FullName set to the NodeId.ToString() serialization so IReadable/IWritable can round-trip without re-resolving. Three safety caps added to OpcUaClientDriverOptions to bound runaway discovery: (1) MaxBrowseDepth default 10 -- deep enough for realistic OPC UA information models, shallow enough that cyclic graphs can't spin the browse forever. (2) MaxDiscoveredNodes default 10_000 -- caps memory on pathological remote servers. Once the cap is hit, recursion short-circuits and the partially-discovered tree is still projected into the local address space (graceful degradation rather than all-or-nothing). (3) BrowseRoot as an opt-in scope restriction string per driver-specs.md \u00A78 -- defaults to ObjectsFolder but operators with 100k-node servers can point it at a single subtree. Visited-set tracks NodeIds already visited to prevent infinite cycles on graphs with non-strict hierarchy (OPC UA models can have back-references). Transient browse failures on a subtree are swallowed -- the sub-branch stops but the rest of discovery continues, matching the Modbus driver's 'transient poll errors don't kill the loop' pattern. The driver's health surface reflects the network-level cascade via the probe loop (PR 69). Deferred to a follow-up PR: DataType resolution via a batch Session.ReadAsync(Attributes.DataType) after the browse so DriverAttributeInfo.DriverDataType is accurate instead of the current conservative DriverDataType.Int32 default; AccessLevel-derived SecurityClass instead of the current ViewOnly default; array-type detection via Attributes.ValueRank + ArrayDimensions. These need an extra wire round-trip per batch of variables + a NodeId -> DriverDataType mapping table; out of scope for PR 68 to keep browse path landable. Unit tests (OpcUaClientDiscoveryTests, 3 facts): DiscoverAsync_without_initialize_throws_InvalidOperationException (pre-init hits RequireSession); DiscoverAsync_rejects_null_builder (ArgumentNullException); Discovery_caps_are_sensible_defaults (asserts 10000 / 10 / null defaults documented above). NullAddressSpaceBuilder stub implements the full IAddressSpaceBuilder shape including IVariableHandle.MarkAsAlarmCondition (throws NotSupportedException since this PR doesn't wire alarms). Live-browse coverage against a real remote server is deferred to the in-process-server-fixture PR. 10/10 OpcUaClient.Tests pass. dotnet build clean.
This commit is contained in:
Joseph Doherty
@@ -27,7 +27,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient;
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/// </para>
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/// </remarks>
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public sealed class OpcUaClientDriver(OpcUaClientDriverOptions options, string driverInstanceId)
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: IDriver, IReadable, IWritable, IDisposable, IAsyncDisposable
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: IDriver, ITagDiscovery, IReadable, IWritable, IDisposable, IAsyncDisposable
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{
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// OPC UA StatusCode constants the driver surfaces for local-side faults. Upstream-server
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// StatusCodes are passed through verbatim per driver-specs.md §8 "cascading quality" —
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@@ -380,6 +380,110 @@ public sealed class OpcUaClientDriver(OpcUaClientDriverOptions options, string d
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private ISession RequireSession() =>
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Session ?? throw new InvalidOperationException("OpcUaClientDriver not initialized");
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// ---- ITagDiscovery ----
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public async Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken)
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{
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ArgumentNullException.ThrowIfNull(builder);
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var session = RequireSession();
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var root = !string.IsNullOrEmpty(_options.BrowseRoot)
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? NodeId.Parse(session.MessageContext, _options.BrowseRoot)
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: ObjectIds.ObjectsFolder;
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var rootFolder = builder.Folder("Remote", "Remote");
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var visited = new HashSet<NodeId>();
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var discovered = 0;
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await _gate.WaitAsync(cancellationToken).ConfigureAwait(false);
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try
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{
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await BrowseRecursiveAsync(session, root, rootFolder, visited,
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depth: 0, discovered: () => discovered, increment: () => discovered++,
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ct: cancellationToken).ConfigureAwait(false);
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}
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finally { _gate.Release(); }
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}
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private async Task BrowseRecursiveAsync(
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ISession session, NodeId node, IAddressSpaceBuilder folder, HashSet<NodeId> visited,
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int depth, Func<int> discovered, Action increment, CancellationToken ct)
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{
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if (depth >= _options.MaxBrowseDepth) return;
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if (discovered() >= _options.MaxDiscoveredNodes) return;
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if (!visited.Add(node)) return;
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var browseDescriptions = new BrowseDescriptionCollection
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{
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new()
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{
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NodeId = node,
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BrowseDirection = BrowseDirection.Forward,
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ReferenceTypeId = ReferenceTypeIds.HierarchicalReferences,
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IncludeSubtypes = true,
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NodeClassMask = (uint)(NodeClass.Object | NodeClass.Variable),
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ResultMask = (uint)(BrowseResultMask.BrowseName | BrowseResultMask.DisplayName
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| BrowseResultMask.NodeClass | BrowseResultMask.TypeDefinition),
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}
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};
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BrowseResponse resp;
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try
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{
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resp = await session.BrowseAsync(
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requestHeader: null,
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view: null,
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requestedMaxReferencesPerNode: 0,
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nodesToBrowse: browseDescriptions,
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ct: ct).ConfigureAwait(false);
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}
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catch
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{
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// Transient browse failure on a sub-tree — don't kill the whole discovery, just
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// skip this branch. The driver's health surface will reflect the cascade via the
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// probe loop (PR 69).
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return;
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}
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if (resp.Results.Count == 0) return;
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var refs = resp.Results[0].References;
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foreach (var rf in refs)
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{
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if (discovered() >= _options.MaxDiscoveredNodes) break;
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var childId = ExpandedNodeId.ToNodeId(rf.NodeId, session.NamespaceUris);
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if (NodeId.IsNull(childId)) continue;
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var browseName = rf.BrowseName?.Name ?? childId.ToString();
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var displayName = rf.DisplayName?.Text ?? browseName;
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if (rf.NodeClass == NodeClass.Object)
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{
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var subFolder = folder.Folder(browseName, displayName);
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increment();
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await BrowseRecursiveAsync(session, childId, subFolder, visited,
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depth + 1, discovered, increment, ct).ConfigureAwait(false);
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}
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else if (rf.NodeClass == NodeClass.Variable)
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{
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// Serialize the NodeId so the IReadable/IWritable surface receives a
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// round-trippable string. Deferring the DataType + AccessLevel fetch to a
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// follow-up PR — initial browse uses a conservative ViewOnly + Int32 default.
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var nodeIdString = childId.ToString() ?? string.Empty;
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folder.Variable(browseName, displayName, new DriverAttributeInfo(
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FullName: nodeIdString,
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DriverDataType: DriverDataType.Int32,
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IsArray: false,
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ArrayDim: null,
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SecurityClass: SecurityClassification.ViewOnly,
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IsHistorized: false,
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IsAlarm: false));
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increment();
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}
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}
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}
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public void Dispose() => DisposeAsync().AsTask().GetAwaiter().GetResult();
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public async ValueTask DisposeAsync()
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