feat(opcuaclient.browser): add lazy browse session impl
This commit is contained in:
Joseph Doherty
@@ -0,0 +1,178 @@
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using Opc.Ua;
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using Opc.Ua.Client;
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using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
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using ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient;
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namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser;
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/// <summary>
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/// Live one-level-per-call browse session over a remote OPC UA server. Created by
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/// <c>OpcUaClientBrowser</c> on picker open and owned by the AdminUI's
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/// <c>BrowseSessionRegistry</c>; the registry's TTL reaper disposes idle sessions.
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/// </summary>
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internal sealed class OpcUaClientBrowseSession : IBrowseSession
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{
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private readonly ISession _session;
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private readonly NamespaceMap _nsMap;
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private readonly NodeId _rootNodeId;
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private readonly SemaphoreSlim _gate = new(1, 1);
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private bool _disposed;
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/// <summary>
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/// Construct a browse session bound to an already-connected <paramref name="session"/>.
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/// </summary>
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/// <param name="session">The OPC UA client session to browse against.</param>
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/// <param name="nsMap">Namespace snapshot taken at connect time; used to render outbound
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/// NodeIds in the server-stable <c>nsu=…</c> form.</param>
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/// <param name="rootNodeId">The node under which <see cref="RootAsync"/> browses one level.</param>
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internal OpcUaClientBrowseSession(ISession session, NamespaceMap nsMap, NodeId rootNodeId)
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{
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_session = session;
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_nsMap = nsMap;
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_rootNodeId = rootNodeId;
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}
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/// <summary>Opaque token identifying this session in the AdminUI registry.</summary>
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public Guid Token { get; } = Guid.NewGuid();
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/// <summary>Wall-clock time of the most recent successful browse call; the reaper uses
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/// this for idle eviction.</summary>
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public DateTime LastUsedUtc { get; private set; } = DateTime.UtcNow;
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/// <summary>Browse one level under the configured root node.</summary>
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/// <param name="cancellationToken">Cancellation token.</param>
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public Task<IReadOnlyList<BrowseNode>> RootAsync(CancellationToken cancellationToken)
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=> BrowseOneLevelAsync(_rootNodeId, cancellationToken);
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/// <summary>Browse one level under the node identified by <paramref name="nodeId"/>,
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/// which must be a stable reference produced by <see cref="NamespaceMap.ToStableReference"/>
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/// (or a plain <c>ns=N;…</c> form).</summary>
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/// <param name="nodeId">Stable reference string for the parent node.</param>
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/// <param name="cancellationToken">Cancellation token.</param>
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/// <exception cref="ArgumentException">Thrown when <paramref name="nodeId"/> cannot be
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/// resolved against the live session's namespace table.</exception>
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public Task<IReadOnlyList<BrowseNode>> ExpandAsync(string nodeId, CancellationToken cancellationToken)
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{
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if (!NamespaceMap.TryResolve(_session, nodeId, out var resolved))
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throw new ArgumentException(
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$"Cannot resolve NodeId '{nodeId}' against the live session.", nameof(nodeId));
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return BrowseOneLevelAsync(resolved, cancellationToken);
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}
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/// <summary>The OPC UA picker treats variables as terminal leaves and does not surface
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/// a per-attribute side-panel, so this always returns empty.</summary>
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/// <param name="nodeId">Ignored.</param>
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/// <param name="cancellationToken">Ignored.</param>
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public Task<IReadOnlyList<AttributeInfo>> AttributesAsync(string nodeId, CancellationToken cancellationToken)
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=> Task.FromResult<IReadOnlyList<AttributeInfo>>(Array.Empty<AttributeInfo>());
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/// <summary>Issue a single-level Browse (plus continuation-point follow-ups) under the
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/// given parent node. <see cref="Session.BrowseAsync"/> is not thread-safe, so all calls
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/// serialize through <see cref="_gate"/>.</summary>
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private async Task<IReadOnlyList<BrowseNode>> BrowseOneLevelAsync(NodeId parent, CancellationToken ct)
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{
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ObjectDisposedException.ThrowIf(_disposed, this);
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await _gate.WaitAsync(ct).ConfigureAwait(false);
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try
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{
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var descriptions = new BrowseDescriptionCollection
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{
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new()
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{
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NodeId = parent,
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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),
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},
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};
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var 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: descriptions,
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ct: ct).ConfigureAwait(false);
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if (resp.Results.Count == 0)
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{
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LastUsedUtc = DateTime.UtcNow;
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return Array.Empty<BrowseNode>();
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}
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var result = resp.Results[0];
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var refs = result.References;
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// Follow browse continuation points so folders larger than the server's per-call
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// cap aren't silently truncated (same pattern as runtime
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// Driver.OpcUaClient-003).
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var cp = result.ContinuationPoint;
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while (cp is { Length: > 0 })
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{
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var next = await _session.BrowseNextAsync(
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requestHeader: null,
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releaseContinuationPoints: false,
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continuationPoints: [cp],
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ct: ct).ConfigureAwait(false);
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if (next.Results.Count == 0) break;
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var nextResult = next.Results[0];
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if (nextResult.References is { Count: > 0 })
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refs.AddRange(nextResult.References);
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cp = nextResult.ContinuationPoint;
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}
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LastUsedUtc = DateTime.UtcNow;
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var nodes = new List<BrowseNode>(refs.Count);
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foreach (var rf in refs)
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nodes.Add(ToBrowseNode(rf));
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return nodes;
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}
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finally
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{
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_gate.Release();
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}
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}
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/// <summary>Project a single <see cref="ReferenceDescription"/> into the driver-agnostic
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/// <see cref="BrowseNode"/> shape, encoding the outbound NodeId in the stable
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/// <c>nsu=…</c> form so the picker survives a remote namespace-table reorder.</summary>
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private BrowseNode ToBrowseNode(ReferenceDescription rf)
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{
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var childId = ExpandedNodeId.ToNodeId(rf.NodeId, _session.NamespaceUris);
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var isObject = rf.NodeClass == NodeClass.Object;
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var displayName = rf.DisplayName?.Text
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?? rf.BrowseName?.Name
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?? childId.ToString()
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?? "(unnamed)";
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return new BrowseNode(
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NodeId: _nsMap.ToStableReference(childId),
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DisplayName: displayName,
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Kind: isObject ? BrowseNodeKind.Folder : BrowseNodeKind.Leaf,
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HasChildrenHint: isObject);
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}
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/// <summary>Idempotent best-effort dispose: closes the underlying session if it's a
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/// concrete <see cref="Session"/>, disposes it, and disposes the gate. Close errors are
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/// swallowed because the registry reaper may be racing a remote disconnect.</summary>
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public async ValueTask DisposeAsync()
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{
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if (_disposed) return;
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_disposed = true;
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if (_session is Session s)
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{
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try { await s.CloseAsync().ConfigureAwait(false); }
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catch { /* best-effort */ }
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}
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try { _session.Dispose(); }
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catch { /* best-effort */ }
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try { _gate.Dispose(); }
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catch { /* best-effort */ }
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}
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}
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