fix(network): tolerate slp ping failures

Author: lxhtt

MCServerLauncher.Common/Network/SlpClient.cs

@@ -26,14 +26,27 @@ public class SlpClient
     {
         if (port < 0 || port > 65535) throw new ArgumentOutOfRangeException(nameof(port));
 
-        var client = new SlpClient();
-        if (!await client.HandShakeAsync(host, (ushort)port, cancellationToken)) return null;
+        try
+        {
+            var client = new SlpClient();
+            if (!await client.HandShakeAsync(host, (ushort)port, cancellationToken)) return null;
 
-        var payload = await client.GetSlpAsync(cancellationToken);
-        var latency = await client.GetLatencyAsync(cancellationToken);
+            var payload = await client.GetSlpAsync(cancellationToken);
+            if (payload is null) return null;
 
-        if (payload != null && latency != null) return new SlpStatus(payload, latency.Value);
-        return null;
+            var latency = await client.GetLatencyAsync(cancellationToken);
+
+            return latency != null ? new SlpStatus(payload, latency.Value) : null;
+        }
+        catch (OperationCanceledException)
+        {
+            throw;
+        }
+        catch (Exception e) when (e is SocketException or IOException)
+        {
+            Log.Debug(e, "[SlpClient] Modern server ping failed for {Host}:{Port}", host, port);
+            return null;
+        }
     }
 
     /// <summary>

MCServerLauncher.Daemon/Management/Minecraft/MinecraftInstance.cs

@@ -1,7 +1,7 @@
-using System.Net.Sockets;
 using MCServerLauncher.Common.Minecraft;
 using MCServerLauncher.Common.Network;
 using MCServerLauncher.Common.ProtoType.Instance;
+using Serilog;
 
 namespace MCServerLauncher.Daemon.Management.Minecraft;
 
@@ -43,8 +43,13 @@ private async Task<Player[]> GetServerPlayersAsync(CancellationToken ct = defaul
                 if (status != null)
                     return status.Payload.Players.Sample.Select(player => new Player(player.Name, player.Id)).ToArray();
             }
-            catch (Exception e)when (e is SocketException or ArgumentOutOfRangeException or ArgumentException)
+            catch (OperationCanceledException) when (ct.IsCancellationRequested)
             {
+                throw;
+            }
+            catch (Exception e)
+            {
+                Log.Debug(e, "[MinecraftInstance] Failed to query server player list for instance {InstanceId}", Config.Uuid);
                 return [];
             }
 

MCServerLauncher.ProtocolTests/SlpClientFailureToleranceTests.cs

@@ -0,0 +1,33 @@
+using System.Net;
+using System.Net.Sockets;
+using MCServerLauncher.Common.Network;
+
+namespace MCServerLauncher.ProtocolTests;
+
+public class SlpClientFailureToleranceTests
+{
+    [Fact]
+    public async Task GetStatusModern_InvalidStatusPayload_ReturnsNullWithoutLatencyWrite()
+    {
+        using var listener = new TcpListener(IPAddress.Loopback, 0);
+        listener.Start();
+
+        var port = ((IPEndPoint)listener.LocalEndpoint).Port;
+        var serverTask = Task.Run(async () =>
+        {
+            using var client = await listener.AcceptTcpClientAsync();
+            client.LingerState = new LingerOption(true, 0);
+
+            using var stream = client.GetStream();
+            var buffer = new byte[512];
+            await stream.ReadAtLeastAsync(buffer, 1);
+
+            await stream.WriteAsync(new byte[] { 0x02, 0x00, 0x00 });
+        });
+
+        var result = await SlpClient.GetStatusModern(IPAddress.Loopback.ToString(), port);
+
+        Assert.Null(result);
+        await serverTask.WaitAsync(TimeSpan.FromSeconds(3));
+    }
+}

docs/superpowers/plans/2026-06-19-slp-report-failure-tolerance.md

@@ -0,0 +1,72 @@
+# SLP Report Failure Tolerance Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Prevent Minecraft SLP ping/player-list failures from breaking daemon instance report refresh.
+
+**Architecture:** Treat Minecraft server-list ping as best-effort report enrichment. `SlpClient.GetStatusModern` should stop after an invalid status payload instead of reusing a failed connection for latency, and daemon Minecraft report generation should convert non-cancellation SLP failures into an empty player list.
+
+**Tech Stack:** C# 14, .NET 10, System.Net.Sockets, xUnit protocol tests.
+
+---
+
+## File Structure
+
+- Modify: `MCServerLauncher.Common/Network/SlpClient.cs`
+  - Owns modern Minecraft SLP status and latency probing.
+- Modify: `MCServerLauncher.Daemon/Management/Minecraft/MinecraftInstance.cs`
+  - Owns Minecraft-specific report enrichment for online players.
+- Create: `MCServerLauncher.ProtocolTests/SlpClientFailureToleranceTests.cs`
+  - Verifies invalid SLP status payloads return `null` without a follow-up latency write.
+
+## Task 1: Add SLP Failure Regression Test
+
+- [x] **Step 1: Write the failing test**
+
+Create `MCServerLauncher.ProtocolTests/SlpClientFailureToleranceTests.cs` with a loopback `TcpListener` that accepts the status request, sends an invalid/empty status response, then closes the connection. Assert `SlpClient.GetStatusModern` returns `null` instead of throwing.
+
+- [x] **Step 2: Run test to verify it fails**
+
+Run:
+
+```powershell
+dotnet test MCServerLauncher.ProtocolTests/MCServerLauncher.ProtocolTests.csproj -c Release --filter "FullyQualifiedName~SlpClientFailureToleranceTests"
+```
+
+Expected before implementation: FAIL due `IOException` when the client tries to write the latency packet after invalid status.
+
+- [x] **Step 3: Implement minimal common-layer fix**
+
+In `SlpClient.GetStatusModern`, return `null` immediately when `GetSlpAsync` returns `null`; only call `GetLatencyAsync` after a valid status payload.
+
+- [x] **Step 4: Add daemon-side defense**
+
+In `MinecraftInstance.GetServerPlayersAsync`, let caller-requested cancellation propagate and catch other SLP/report enrichment exceptions as an empty player list.
+
+- [x] **Step 5: Verify focused test**
+
+Run:
+
+```powershell
+dotnet test MCServerLauncher.ProtocolTests/MCServerLauncher.ProtocolTests.csproj -c Release --filter "FullyQualifiedName~SlpClientFailureToleranceTests"
+```
+
+Expected after implementation: PASS.
+
+- [x] **Step 6: Verify relevant project and hygiene**
+
+Run:
+
+```powershell
+dotnet build MCServerLauncher.Daemon/MCServerLauncher.Daemon.csproj /m:1
+dotnet test MCServerLauncher.ProtocolTests/MCServerLauncher.ProtocolTests.csproj -c Release --no-build
+git diff --check
+```
+
+Expected: commands exit 0.
+
+## Changelog
+
+- Added regression coverage for invalid Minecraft SLP status responses closing before latency ping.
+- Updated modern SLP probing to stop after invalid status payloads.
+- Hardened Minecraft instance report enrichment so player-list probe failures do not fail `GetAllReports`.