chore: initial project import

backend/probe/src/Monitor.Probe/Link/AgentDirectory.cs

@@ -0,0 +1,105 @@
+using System.Text.Json;
+using Fleet.Core;
+using Fleet.Hosting;
+using Monitor.Protocol;
+
+namespace Monitor.Probe;
+
+/// <summary>
+/// Probe 要连接的 Agent 列表。Probe 不认识 Backend：列表先取自 <c>probe.json</c> 的 bootstrap（或上一次保存的 <c>agents.json</c>），
+/// 连上任意一个 Agent 之后，由它代为向 Backend 查询（<c>monitor.probe.agents</c>），之后的变化由 Agent 推送（<c>agents_changed</c>）。
+/// 列表变化时用 <see cref="ConfigStore"/> 写回 <c>agents.json</c>（这是配置，不是测量数据；只在变化时写，保护路由器的闪存）。
+/// </summary>
+public sealed class AgentDirectory
+{
+    public const string FileName = "agents.json";
+
+    private readonly object _gate = new();
+    private readonly ConfigStore _store;
+    private readonly INodeLog _log;
+    private List<BootstrapAgent> _agents;
+    private long _version;
+
+    public AgentDirectory(ConfigStore store, string configDirectory, ProbeFile file, INodeLog log)
+    {
+        _store = store;
+        _log = log;
+        _agents = [.. file.Bootstrap];
+        string cache = Path.Combine(configDirectory, FileName);
+        if (File.Exists(cache))
+        {
+            try
+            {
+                AgentsCache saved = NodeConfig.Load(cache, ProbeConfigContext.Default.AgentsCache);
+                if (saved.Agents.Count > 0)
+                {
+                    _agents = saved.Agents;
+                    _version = saved.Version;
+                }
+            }
+            catch (Exception ex) when (ex is IOException or InvalidDataException or JsonException or InvalidOperationException)
+            {
+                _log.Warn("agents.json is unreadable, using the bootstrap list", ("err", ex.Message));
+            }
+        }
+    }
+
+    /// <summary>列表变化（调和连接）。</summary>
+    public event Action? Changed;
+
+    public long Version
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return _version;
+            }
+        }
+    }
+
+    public IReadOnlyList<BootstrapAgent> Agents
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return [.. _agents];
+            }
+        }
+    }
+
+    /// <summary>应用 Agent 转来的列表。版本不比当前新的忽略（乱序到达的旧推送）。</summary>
+    public void Apply(ProbeAgentsResult result)
+    {
+        var next = result.Agents.Select(a => new BootstrapAgent { AgentId = a.AgentId.Value, Host = a.Host, TcpPort = a.TcpPort, Spki = a.Spki }).ToList();
+        lock (_gate)
+        {
+            if (result.Version < _version || (result.Version == _version && Same(next, _agents)))
+            {
+                return;
+            }
+
+            _version = result.Version;
+            _agents = next;
+        }
+
+        try
+        {
+            _store.Write(FileName, JsonSerializer.SerializeToUtf8Bytes(new AgentsCache { Version = result.Version, Agents = next }, ProbeConfigContext.Default.AgentsCache));
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            _log.Warn("could not save agents.json", ("err", ex.Message));
+        }
+
+        _log.Info("agent list updated", ("version", result.Version), ("agents", next.Count));
+        Changed?.Invoke();
+    }
+
+    private static bool Same(List<BootstrapAgent> a, List<BootstrapAgent> b) =>
+        a.Count == b.Count && a.Zip(b).All(p => Equal(p.First, p.Second));
+
+    public static bool Equal(BootstrapAgent a, BootstrapAgent b) =>
+        a.AgentId == b.AgentId && a.Host == b.Host && a.TcpPort == b.TcpPort && a.Spki == b.Spki;
+}