feat(batch27): implement jetstream config validation and error tail

dotnet/src/ZB.MOM.NatsNet.Server/NatsServer.JetStreamCore.cs

@@ -7,6 +7,7 @@ namespace ZB.MOM.NatsNet.Server;
 public sealed partial class NatsServer
 {
     private const string JetStreamStoreDir = "jetstream";
+    private const long JetStreamMaxMemDefault = 1024L * 1024L * 256L;
 
     public Exception? EnableJetStream(JetStreamConfig? config)
     {
@@ -495,6 +496,81 @@ public sealed partial class NatsServer
             null);
     }
 
+    internal JetStreamConfig DynJetStreamConfig(string storeDir, long maxStore, long maxMem)
+    {
+        var cfg = new JetStreamConfig();
+        if (!string.IsNullOrWhiteSpace(storeDir))
+        {
+            cfg.StoreDir = Path.Combine(storeDir, JetStreamStoreDir);
+        }
+        else
+        {
+            cfg.StoreDir = Path.Combine(Path.GetTempPath(), "nats", JetStreamStoreDir);
+            Warnf("Temporary storage directory used, data could be lost on system reboot");
+        }
+
+        var opts = GetOpts();
+        cfg.Strict = !opts.NoJetStreamStrict;
+        cfg.SyncInterval = opts.SyncInterval;
+        cfg.SyncAlways = opts.SyncAlways;
+
+        cfg.MaxStore = opts.MaxStoreSet && maxStore >= 0
+            ? maxStore
+            : DiskAvailability.DiskAvailable(cfg.StoreDir);
+
+        if (opts.MaxMemSet && maxMem >= 0)
+        {
+            cfg.MaxMemory = maxMem;
+        }
+        else
+        {
+            var totalAvailable = GC.GetGCMemoryInfo().TotalAvailableMemoryBytes;
+            cfg.MaxMemory = totalAvailable > 0 && totalAvailable < long.MaxValue
+                ? totalAvailable / 4 * 3
+                : JetStreamMaxMemDefault;
+        }
+
+        return cfg;
+    }
+
+    internal void ResourcesExceededError(StorageType storeType)
+    {
+        var didAlert = false;
+        lock (_resourceErrorLock)
+        {
+            var now = DateTime.UtcNow;
+            if (now - _resourceErrorLastUtc > TimeSpan.FromSeconds(10))
+            {
+                var storeName = storeType switch
+                {
+                    StorageType.MemoryStorage => "memory",
+                    StorageType.FileStorage => "file",
+                    _ => storeType.ToString().ToLowerInvariant(),
+                };
+
+                Errorf("JetStream {0} resource limits exceeded for server", storeName);
+                _resourceErrorLastUtc = now;
+                didAlert = true;
+            }
+        }
+
+        if (!didAlert)
+            return;
+
+        var js = GetJetStreamState();
+        if (js?.Cluster is JetStreamCluster { Meta: not null } cluster)
+            cluster.Meta.StepDown();
+    }
+
+    internal void HandleWritePermissionError()
+    {
+        if (!JetStreamEnabled())
+            return;
+
+        Errorf("File system permission denied while writing, disabling JetStream");
+        _ = Task.Run(() => DisableJetStream());
+    }
+
     internal JetStreamEngine? GetJetStream() =>
         _jetStream == null ? null : new JetStreamEngine(_jetStream);