feat(adminui): in-process browse session registry + TTL reaper + service

2026-05-28 15:36:19 -04:00
parent 7cd5cde315
commit bec2988309
4 changed files with 217 additions and 0 deletions
@@ -0,0 +1,67 @@
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Browsing;
+
+/// <summary>
+///     Background service that periodically evicts idle browse sessions from the
+///     <see cref="BrowseSessionRegistry"/>. Each tick takes a snapshot of the registry,
+///     removes any session that has been idle longer than <see cref="IdleTtl"/>, then
+///     disposes the evicted instance OUTSIDE the dictionary — so concurrent expand
+///     calls racing eviction fail cleanly via <see cref="BrowseSessionNotFoundException"/>.
+/// </summary>
+public sealed class BrowseSessionReaper(
+    BrowseSessionRegistry registry,
+    ILogger<BrowseSessionReaper> logger) : BackgroundService
+{
+    /// <summary>How long a session may be untouched before it becomes eligible for eviction.</summary>
+    public static readonly TimeSpan IdleTtl = TimeSpan.FromMinutes(2);
+
+    /// <summary>How often the reaper checks the registry.</summary>
+    public static readonly TimeSpan TickInterval = TimeSpan.FromSeconds(30);
+
+    /// <inheritdoc />
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        using var timer = new PeriodicTimer(TickInterval);
+        while (!stoppingToken.IsCancellationRequested &&
+               await timer.WaitForNextTickAsync(stoppingToken).ConfigureAwait(false))
+        {
+            try { await ReapOnceAsync(stoppingToken).ConfigureAwait(false); }
+            catch (Exception ex)
+            {
+                logger.LogWarning(ex, "Browse-session reaper iteration failed; will retry next tick.");
+            }
+        }
+        await DrainAllAsync().ConfigureAwait(false);
+    }
+
+    /// <summary>Evicts every session whose <see cref="Commons.Browsing.IBrowseSession.LastUsedUtc"/>
+    /// is older than <see cref="IdleTtl"/>. Internal so tests can drive a tick directly.</summary>
+    internal async Task ReapOnceAsync(CancellationToken ct)
+    {
+        var now = DateTime.UtcNow;
+        foreach (var (token, session) in registry.Snapshot())
+        {
+            if (now - session.LastUsedUtc < IdleTtl) continue;
+            if (!registry.TryRemove(token, out var taken)) continue;
+            try { await taken.DisposeAsync().ConfigureAwait(false); }
+            catch (Exception ex)
+            {
+                logger.LogDebug(ex,
+                    "Best-effort dispose of idle-evicted browse session {Token} failed.", token);
+            }
+            logger.LogDebug("Browse session {Token} closed reason=idle-ttl", token);
+        }
+    }
+
+    private async Task DrainAllAsync()
+    {
+        foreach (var (token, session) in registry.Snapshot())
+        {
+            if (!registry.TryRemove(token, out var taken)) continue;
+            try { await taken.DisposeAsync().ConfigureAwait(false); } catch { }
+            logger.LogDebug("Browse session {Token} closed reason=shutdown", token);
+        }
+    }
+}