feat(adminui): in-process browse session registry + TTL reaper + service
This commit is contained in:
Joseph Doherty
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using Microsoft.Extensions.Hosting;
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using Microsoft.Extensions.Logging;
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namespace ZB.MOM.WW.OtOpcUa.AdminUI.Browsing;
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/// <summary>
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/// Background service that periodically evicts idle browse sessions from the
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/// <see cref="BrowseSessionRegistry"/>. Each tick takes a snapshot of the registry,
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/// removes any session that has been idle longer than <see cref="IdleTtl"/>, then
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/// disposes the evicted instance OUTSIDE the dictionary — so concurrent expand
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/// calls racing eviction fail cleanly via <see cref="BrowseSessionNotFoundException"/>.
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/// </summary>
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public sealed class BrowseSessionReaper(
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BrowseSessionRegistry registry,
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ILogger<BrowseSessionReaper> logger) : BackgroundService
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{
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/// <summary>How long a session may be untouched before it becomes eligible for eviction.</summary>
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public static readonly TimeSpan IdleTtl = TimeSpan.FromMinutes(2);
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/// <summary>How often the reaper checks the registry.</summary>
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public static readonly TimeSpan TickInterval = TimeSpan.FromSeconds(30);
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/// <inheritdoc />
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protected override async Task ExecuteAsync(CancellationToken stoppingToken)
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{
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using var timer = new PeriodicTimer(TickInterval);
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while (!stoppingToken.IsCancellationRequested &&
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await timer.WaitForNextTickAsync(stoppingToken).ConfigureAwait(false))
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{
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try { await ReapOnceAsync(stoppingToken).ConfigureAwait(false); }
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catch (Exception ex)
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{
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logger.LogWarning(ex, "Browse-session reaper iteration failed; will retry next tick.");
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}
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}
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await DrainAllAsync().ConfigureAwait(false);
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}
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/// <summary>Evicts every session whose <see cref="Commons.Browsing.IBrowseSession.LastUsedUtc"/>
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/// is older than <see cref="IdleTtl"/>. Internal so tests can drive a tick directly.</summary>
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internal async Task ReapOnceAsync(CancellationToken ct)
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{
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var now = DateTime.UtcNow;
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foreach (var (token, session) in registry.Snapshot())
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{
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if (now - session.LastUsedUtc < IdleTtl) continue;
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if (!registry.TryRemove(token, out var taken)) continue;
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try { await taken.DisposeAsync().ConfigureAwait(false); }
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catch (Exception ex)
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{
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logger.LogDebug(ex,
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"Best-effort dispose of idle-evicted browse session {Token} failed.", token);
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}
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logger.LogDebug("Browse session {Token} closed reason=idle-ttl", token);
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}
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}
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private async Task DrainAllAsync()
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{
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foreach (var (token, session) in registry.Snapshot())
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{
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if (!registry.TryRemove(token, out var taken)) continue;
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try { await taken.DisposeAsync().ConfigureAwait(false); } catch { }
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logger.LogDebug("Browse session {Token} closed reason=shutdown", token);
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}
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}
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}
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@@ -0,0 +1,30 @@
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using System.Collections.Concurrent;
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using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
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namespace ZB.MOM.WW.OtOpcUa.AdminUI.Browsing;
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/// <summary>
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/// Singleton in-process directory of live <see cref="IBrowseSession"/> instances,
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/// keyed by <see cref="IBrowseSession.Token"/>. Concurrency is provided by the
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/// underlying <see cref="ConcurrentDictionary{TKey, TValue}"/> alone — there are no
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/// additional locks; callers must dispose evicted sessions outside the dictionary.
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/// </summary>
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public sealed class BrowseSessionRegistry
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{
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private readonly ConcurrentDictionary<Guid, IBrowseSession> _sessions = new();
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/// <summary>Adds (or replaces) a session in the registry keyed by its token.</summary>
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public void Register(IBrowseSession session) => _sessions[session.Token] = session;
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/// <summary>Looks up a session by token without removing it.</summary>
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public bool TryGet(Guid token, out IBrowseSession session) =>
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_sessions.TryGetValue(token, out session!);
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/// <summary>Atomically removes a session from the registry, returning it for disposal.</summary>
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public bool TryRemove(Guid token, out IBrowseSession session) =>
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_sessions.TryRemove(token, out session!);
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/// <summary>Returns a point-in-time snapshot of all currently registered sessions.</summary>
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public IReadOnlyList<(Guid Token, IBrowseSession Session)> Snapshot() =>
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_sessions.Select(kv => (kv.Key, kv.Value)).ToList();
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}
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@@ -0,0 +1,72 @@
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using Microsoft.Extensions.Logging;
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using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
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namespace ZB.MOM.WW.OtOpcUa.AdminUI.Browsing;
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/// <summary>
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/// Default <see cref="IBrowserSessionService"/> implementation. Indexes injected
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/// <see cref="IDriverBrowser"/>s by <see cref="IDriverBrowser.DriverType"/>
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/// (case-insensitive) at construction, registers opened sessions, and wraps each
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/// expand/attributes call in a 20-second linked CTS so a stuck driver cannot
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/// stall the UI indefinitely.
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/// </summary>
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public sealed class BrowserSessionService(
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IEnumerable<IDriverBrowser> browsers,
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BrowseSessionRegistry registry,
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ILogger<BrowserSessionService> logger) : IBrowserSessionService
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{
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/// <summary>Upper bound on a single root/expand/attributes call.</summary>
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public static readonly TimeSpan PerCallTimeout = TimeSpan.FromSeconds(20);
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private readonly IReadOnlyDictionary<string, IDriverBrowser> _browsersByType =
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browsers.ToDictionary(b => b.DriverType, StringComparer.OrdinalIgnoreCase);
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/// <inheritdoc />
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public async Task<BrowseOpenResult> OpenAsync(string driverType, string configJson, CancellationToken ct)
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{
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if (!_browsersByType.TryGetValue(driverType, out var browser))
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return new(false, $"No browser registered for driver type '{driverType}'.", Guid.Empty);
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try
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{
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var session = await browser.OpenAsync(configJson, ct).ConfigureAwait(false);
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registry.Register(session);
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return new(true, null, session.Token);
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}
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catch (Exception ex)
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{
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logger.LogInformation(ex,
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"Browser open failed for driverType={DriverType}: {Message}", driverType, ex.Message);
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return new(false, ex.Message, Guid.Empty);
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}
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}
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/// <inheritdoc />
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public Task<IReadOnlyList<BrowseNode>> RootAsync(Guid token, CancellationToken ct) =>
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InvokeAsync(token, ct, (s, c) => s.RootAsync(c));
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/// <inheritdoc />
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public Task<IReadOnlyList<BrowseNode>> ExpandAsync(Guid token, string nodeId, CancellationToken ct) =>
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InvokeAsync(token, ct, (s, c) => s.ExpandAsync(nodeId, c));
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/// <inheritdoc />
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public Task<IReadOnlyList<AttributeInfo>> AttributesAsync(Guid token, string nodeId, CancellationToken ct) =>
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InvokeAsync<IReadOnlyList<AttributeInfo>>(token, ct, (s, c) => s.AttributesAsync(nodeId, c));
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/// <inheritdoc />
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public async Task CloseAsync(Guid token)
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{
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if (!registry.TryRemove(token, out var session)) return;
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try { await session.DisposeAsync().ConfigureAwait(false); } catch { }
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logger.LogDebug("Browse session {Token} closed reason=user-close", token);
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}
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private async Task<T> InvokeAsync<T>(
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Guid token, CancellationToken callerCt, Func<IBrowseSession, CancellationToken, Task<T>> op)
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{
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if (!registry.TryGet(token, out var session))
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throw new BrowseSessionNotFoundException(token);
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using var cts = CancellationTokenSource.CreateLinkedTokenSource(callerCt);
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cts.CancelAfter(PerCallTimeout);
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return await op(session, cts.Token).ConfigureAwait(false);
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}
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}
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@@ -0,0 +1,48 @@
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using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
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namespace ZB.MOM.WW.OtOpcUa.AdminUI.Browsing;
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/// <summary>
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/// Outcome of <see cref="IBrowserSessionService.OpenAsync"/>. On success
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/// <paramref name="Ok"/> is <see langword="true"/> and <paramref name="Token"/> is the
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/// registry handle; on failure <paramref name="Message"/> carries a human-readable
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/// diagnostic for the UI's error chip.
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/// </summary>
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/// <param name="Ok">True iff the browse session was opened and registered.</param>
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/// <param name="Message">Failure diagnostic, or <see langword="null"/> on success.</param>
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/// <param name="Token">Registry handle on success; <see cref="Guid.Empty"/> on failure.</param>
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public sealed record BrowseOpenResult(bool Ok, string? Message, Guid Token);
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/// <summary>
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/// Scoped Razor-page facade over the in-process browse-session machinery. Owns
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/// driver-type dispatch on open and per-call timeout enforcement on expand/attributes.
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/// </summary>
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public interface IBrowserSessionService
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{
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/// <summary>Opens a session against the named driver type using the given JSON config.
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/// Never throws — all errors are surfaced via <see cref="BrowseOpenResult"/>.</summary>
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Task<BrowseOpenResult> OpenAsync(string driverType, string configJson, CancellationToken ct);
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/// <summary>Returns the root nodes of an open session. Throws
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/// <see cref="BrowseSessionNotFoundException"/> if the token is unknown.</summary>
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Task<IReadOnlyList<BrowseNode>> RootAsync(Guid token, CancellationToken ct);
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/// <summary>Returns the direct children of <paramref name="nodeId"/> in an open session.
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/// Throws <see cref="BrowseSessionNotFoundException"/> if the token is unknown.</summary>
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Task<IReadOnlyList<BrowseNode>> ExpandAsync(Guid token, string nodeId, CancellationToken ct);
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/// <summary>Returns the attributes of <paramref name="nodeId"/> in an open session. Throws
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/// <see cref="BrowseSessionNotFoundException"/> if the token is unknown.</summary>
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Task<IReadOnlyList<AttributeInfo>> AttributesAsync(Guid token, string nodeId, CancellationToken ct);
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/// <summary>Removes the session from the registry and disposes it. No-op for unknown tokens.</summary>
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Task CloseAsync(Guid token);
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}
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/// <summary>
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/// Raised by the service layer when a caller references a token that is not
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/// (or no longer) in the registry — typically because the reaper evicted it
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/// between calls.
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/// </summary>
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public sealed class BrowseSessionNotFoundException(Guid token)
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: InvalidOperationException($"Browse session {token} not found (may have been reaped).");
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