Batch full library sync over WebSocket to avoid connection resets.

Large libraries (~30k files) overflowed a single WS message; sync now runs in ACK'd batches with event buffering on the node.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/master-api/src/app.ts

@@ -38,7 +38,12 @@ async function main() {
     timeWindow: "1 minute",
   });
 
-  await app.register(websocket);
+  await app.register(websocket, {
+    options: {
+      // Large library sync batches (still chunked on the node side)
+      maxPayload: 16 * 1024 * 1024,
+    },
+  });
 
   app.addHook("onSend", async (request, reply, payload) => {
     if (!request.url.startsWith("/stremio/")) {

apps/master-api/src/media/sync.ts

@@ -1,61 +1,87 @@
-import type { LibraryEvent } from "@media-cluster/shared-types";
 import { prisma } from "../database/client";
+import type { LibraryEvent } from "@media-cluster/shared-types";
 import { MetadataService } from "../metadata/service";
 
+const PRUNE_CHUNK = 500;
+
 export class LibrarySyncService {
-  constructor(private readonly metadata: MetadataService) {}
+  constructor(private metadata: MetadataService) {}
-
-  async processEvents(nodeId: string, events: LibraryEvent[]): Promise<number> {
-    let maxRevision = 0;
 
+  async processEvents(nodeId: string, events: LibraryEvent[]): Promise<void> {
     for (const event of events) {
-      maxRevision = Math.max(maxRevision, event.nodeRevision);
+      switch (event.type) {
-
+        case "ADDED":
-      if (event.type === "FILE_REMOVED") {
+        case "UPDATED":
+          await this.metadata.matchMediaFile(nodeId, event.file);
+          break;
+        case "REMOVED":
           await prisma.mediaFile.updateMany({
             where: { nodeId, localFileId: event.file.localFileId },
             data: { available: false },
           });
-        continue;
+          break;
+      }
     }
 
-      await this.metadata.matchMediaFile(nodeId, event.file);
+    const lastEvent = events[events.length - 1];
-    }
+    if (lastEvent) {
-
+      const count = await prisma.mediaFile.count({
-    if (maxRevision > 0) {
+        where: { nodeId, available: true },
+      });
       await prisma.node.update({
         where: { id: nodeId },
-        data: { lastRevision: maxRevision },
+        data: {
+          lastRevision: lastEvent.nodeRevision,
+          libraryFileCount: count,
+        },
       });
     }
-
-    return maxRevision;
   }
 
+  /**
+   * Process one FULL_LIBRARY_SYNC message (optionally a batch).
+   * Pruning of files missing from the node only runs when `isLast` is true.
+   */
   async processFullSync(
     nodeId: string,
     nodeRevision: number,
-    files: LibraryEvent["file"][]
+    files: LibraryEvent["file"][],
+    options: {
+      isLast: boolean;
+      fileIdsSoFar: Set<string>;
+    }
   ): Promise<void> {
-    const localFileIds = files.map((f) => f.localFileId);
+    for (const file of files) {
+      options.fileIdsSoFar.add(file.localFileId);
+      await this.metadata.matchMediaFile(nodeId, file);
+    }
 
+    if (!options.isLast) {
+      return;
+    }
+
+    const keepIds = options.fileIdsSoFar;
+    const existing = await prisma.mediaFile.findMany({
+      where: { nodeId },
+      select: { id: true, localFileId: true },
+    });
+    const toDisable = existing
+      .filter((row) => !keepIds.has(row.localFileId))
+      .map((row) => row.id);
+
+    for (let i = 0; i < toDisable.length; i += PRUNE_CHUNK) {
+      const chunk = toDisable.slice(i, i + PRUNE_CHUNK);
       await prisma.mediaFile.updateMany({
-      where: {
+        where: { id: { in: chunk } },
-        nodeId,
-        localFileId: { notIn: localFileIds },
-      },
         data: { available: false },
       });
-
-    for (const file of files) {
-      await this.metadata.matchMediaFile(nodeId, file);
     }
 
     await prisma.node.update({
       where: { id: nodeId },
       data: {
         lastRevision: nodeRevision,
-        libraryFileCount: files.length,
+        libraryFileCount: keepIds.size,
       },
     });
   }

apps/master-api/src/websocket/manager.ts

@@ -27,12 +27,18 @@ interface PendingAck {
   timer: ReturnType<typeof setTimeout>;
 }
 
+interface SyncState {
+  syncId: string;
+  fileIds: Set<string>;
+}
+
 class NodeConnectionManager {
   private connections = new Map<string, NodeConnection>();
   private librarySync: LibrarySyncService | null = null;
   private config: Config | null = null;
   private offlineCheckInterval: ReturnType<typeof setInterval> | null = null;
   private pendingSessionAcks = new Map<string, PendingAck>();
+  private syncState = new Map<string, SyncState>();
 
   init(config: Config): void {
     this.config = config;
@@ -69,6 +75,7 @@ class NodeConnectionManager {
     socket.on("close", () => {
       if (nodeId) {
         this.connections.delete(nodeId);
+        this.syncState.delete(nodeId);
         void prisma.node.update({
           where: { id: nodeId },
           data: { status: "OFFLINE" },
@@ -147,6 +154,7 @@ class NodeConnectionManager {
       return;
     }
 
+    this.syncState.delete(payload.nodeId);
     this.connections.set(payload.nodeId, {
       nodeId: payload.nodeId,
       socket,
@@ -210,6 +218,13 @@ class NodeConnectionManager {
     const conn = [...this.connections.values()].find((c) => c.socket === socket);
     if (!conn || !this.librarySync) return;
 
+    // Don't request another full sync while one is already in progress
+    if (this.syncState.has(conn.nodeId)) {
+      await this.librarySync.processEvents(conn.nodeId, payload.events);
+      this.send(socket, createMessage("LIBRARY_EVENT_ACK", { accepted: true }));
+      return;
+    }
+
     const node = await prisma.node.findUnique({ where: { id: conn.nodeId } });
     if (!node) return;
 
@@ -232,12 +247,49 @@ class NodeConnectionManager {
     const conn = [...this.connections.values()].find((c) => c.socket === socket);
     if (!conn || !this.librarySync) return;
 
+    const syncId = payload.syncId ?? `legacy-${Date.now()}`;
+    const isLast = payload.isLast ?? true;
+    const batchIndex = payload.batchIndex ?? 0;
+
+    let state = this.syncState.get(conn.nodeId);
+    if (!state || state.syncId !== syncId) {
+      state = { syncId, fileIds: new Set() };
+      this.syncState.set(conn.nodeId, state);
+    }
+
+    try {
       await this.librarySync.processFullSync(
         conn.nodeId,
         payload.nodeRevision,
-      payload.files
+        payload.files,
+        { isLast, fileIdsSoFar: state.fileIds }
       );
-    this.send(socket, createMessage("FULL_LIBRARY_SYNC_ACK", { accepted: true }));
+
+      this.send(
+        socket,
+        createMessage("FULL_LIBRARY_SYNC_ACK", {
+          accepted: true,
+          syncId: payload.syncId,
+          batchIndex: payload.batchIndex,
+        })
+      );
+
+      if (isLast) {
+        console.log(
+          `Full library sync complete for ${conn.nodeId}: ${state.fileIds.size} files` +
+            (payload.batchCount != null ? ` (${payload.batchCount} batches)` : "")
+        );
+        this.syncState.delete(conn.nodeId);
+      } else if (batchIndex % 10 === 0) {
+        console.log(
+          `Full library sync progress for ${conn.nodeId}: batch ${(batchIndex ?? 0) + 1}/${payload.batchCount ?? "?"}`
+        );
+      }
+    } catch (err) {
+      console.error(`Full sync failed for ${conn.nodeId}:`, err);
+      this.syncState.delete(conn.nodeId);
+      this.send(socket, createMessage("ERROR", { message: "Full sync failed" }));
+    }
   }
 
   private handlePlaybackSessionAck(payload: CreatePlaybackSessionAckPayload): void {
@@ -309,6 +361,7 @@ class NodeConnectionManager {
     if (conn) {
       conn.socket.close(4004, "Revoked");
       this.connections.delete(nodeId);
+      this.syncState.delete(nodeId);
     }
   }
 
@@ -359,6 +412,7 @@ class NodeConnectionManager {
       conn.socket.close(1001, "Server shutting down");
     }
     this.connections.clear();
+    this.syncState.clear();
   }
 }
 

node/media-node/internal/control/client.go

@@ -21,7 +21,18 @@ import (
 	"github.com/sthmedia/media-node/internal/streaming"
 )
 
-const protocolVersion = 1
+const (
+	protocolVersion     = 1
+	fullSyncBatchSize   = 200
+	writeDeadlineShort  = 15 * time.Second
+	writeDeadlineLong   = 60 * time.Second
+	syncAckTimeout      = 120 * time.Second
+)
+
+type syncAck struct {
+	SyncID     string
+	BatchIndex int
+}
 
 type Client struct {
 	cfg            *config.Config
@@ -35,6 +46,9 @@ type Client struct {
 	connected      bool
 	startTime      time.Time
 	stopCh         chan struct{}
+	syncAckCh      chan syncAck
+	fullSyncActive bool
+	pendingEvents  []scanner.LibraryEvent
 }
 
 func NewClient(
@@ -54,6 +68,7 @@ func NewClient(
 		version:   version,
 		startTime: time.Now(),
 		stopCh:    make(chan struct{}),
+		syncAckCh: make(chan syncAck, 16),
 	}
 }
 
@@ -92,11 +107,18 @@ func (c *Client) Stop() {
 	default:
 		close(c.stopCh)
 	}
+	c.forceClose()
+}
+
+func (c *Client) forceClose() {
 	c.mu.Lock()
-	if c.conn != nil {
+	conn := c.conn
-		_ = c.conn.Close()
+	c.conn = nil
-	}
+	c.connected = false
 	c.mu.Unlock()
+	if conn != nil {
+		_ = conn.Close()
+	}
 }
 
 func (c *Client) connect() error {
@@ -111,12 +133,25 @@ func (c *Client) connect() error {
 	c.mu.Lock()
 	c.conn = conn
 	c.connected = true
+	c.fullSyncActive = false
+	c.pendingEvents = nil
 	c.mu.Unlock()
 
+	// Drain stale ACKs from a previous connection
+	for {
+		select {
+		case <-c.syncAckCh:
+		default:
+			goto drained
+		}
+	}
+drained:
+
 	defer func() {
 		c.mu.Lock()
 		c.connected = false
 		c.conn = nil
+		c.fullSyncActive = false
 		c.mu.Unlock()
 		_ = conn.Close()
 	}()
@@ -159,6 +194,7 @@ func (c *Client) heartbeatLoop(done <-chan struct{}) {
 		case <-ticker.C:
 			if err := c.sendHeartbeat(); err != nil {
 				log.Printf("heartbeat failed: %v", err)
+				c.forceClose()
 				return
 			}
 		}
@@ -189,7 +225,13 @@ func (c *Client) sendHeartbeat() error {
 
 func (c *Client) readLoop() {
 	for {
-		_, data, err := c.conn.ReadMessage()
+		c.mu.Lock()
+		conn := c.conn
+		c.mu.Unlock()
+		if conn == nil {
+			return
+		}
+		_, data, err := conn.ReadMessage()
 		if err != nil {
 			log.Printf("WebSocket read error: %v", err)
 			return
@@ -219,7 +261,20 @@ func (c *Client) handleMessage(msgType string, payload json.RawMessage) {
 			return
 		}
 		log.Println("Connected to Master")
-		c.sendFullSync()
+		// Must run async so readLoop can receive FULL_LIBRARY_SYNC_ACK
+		go c.sendFullSync()
+	case "FULL_LIBRARY_SYNC_ACK":
+		var p struct {
+			Accepted   bool   `json:"accepted"`
+			SyncID     string `json:"syncId"`
+			BatchIndex int    `json:"batchIndex"`
+		}
+		if json.Unmarshal(payload, &p) == nil && p.Accepted {
+			select {
+			case c.syncAckCh <- syncAck{SyncID: p.SyncID, BatchIndex: p.BatchIndex}:
+			default:
+			}
+		}
 	case "CREATE_PLAYBACK_SESSION":
 		var p struct {
 			SessionID          string `json:"sessionId"`
@@ -273,7 +328,7 @@ func (c *Client) handleMessage(msgType string, payload json.RawMessage) {
 	case "RESCAN":
 		go c.scanner.FullScan()
 	case "FULL_LIBRARY_SYNC":
-		c.sendFullSync()
+		go c.sendFullSync()
 	case "CONFIG_UPDATE":
 		log.Println("CONFIG_UPDATE received (apply on next restart)")
 	case "ERROR":
@@ -285,26 +340,117 @@ func (c *Client) SendLibraryEvents(events []scanner.LibraryEvent) {
 	if len(events) == 0 {
 		return
 	}
+
+	c.mu.Lock()
+	if c.fullSyncActive {
+		c.pendingEvents = append(c.pendingEvents, events...)
+		c.mu.Unlock()
+		return
+	}
+	c.mu.Unlock()
+
+	c.flushLibraryEvents(events)
+}
+
+func (c *Client) flushLibraryEvents(events []scanner.LibraryEvent) {
 	msg := controlMessage("LIBRARY_EVENT", map[string]interface{}{
 		"events": events,
 	})
 	if err := c.write(msg); err != nil {
 		log.Printf("failed to send library events: %v", err)
+		c.forceClose()
 	}
 }
 
 func (c *Client) sendFullSync() {
-	files := c.scanner.AllMediaFiles()
+	c.mu.Lock()
-	rev, _ := c.store.MaxRevision()
+	if c.fullSyncActive {
-	msg := controlMessage("FULL_LIBRARY_SYNC", map[string]interface{}{
+		c.mu.Unlock()
-		"nodeRevision": rev,
-		"files":        files,
-	})
-	if err := c.write(msg); err != nil {
-		log.Printf("full library sync failed: %v", err)
 		return
 	}
-	log.Printf("Full library sync sent (%d files)", len(files))
+	c.fullSyncActive = true
+	c.mu.Unlock()
+
+	defer func() {
+		c.mu.Lock()
+		c.fullSyncActive = false
+		pending := c.pendingEvents
+		c.pendingEvents = nil
+		c.mu.Unlock()
+		if len(pending) > 0 {
+			c.flushLibraryEvents(pending)
+		}
+	}()
+
+	files := c.scanner.AllMediaFiles()
+	rev, _ := c.store.MaxRevision()
+	syncID := uuid.New().String()
+
+	batchCount := (len(files) + fullSyncBatchSize - 1) / fullSyncBatchSize
+	if batchCount == 0 {
+		batchCount = 1
+	}
+
+	log.Printf("Starting full library sync (%d files, %d batches)", len(files), batchCount)
+
+	for i := 0; i < batchCount; i++ {
+		start := i * fullSyncBatchSize
+		end := start + fullSyncBatchSize
+		if end > len(files) {
+			end = len(files)
+		}
+		batch := []scanner.MediaFileInfo{}
+		if start < len(files) {
+			batch = files[start:end]
+		}
+
+		// Drain stale ACKs before waiting for this batch
+		for {
+			select {
+			case <-c.syncAckCh:
+			default:
+				goto drained
+			}
+		}
+	drained:
+
+		msg := controlMessage("FULL_LIBRARY_SYNC", map[string]interface{}{
+			"nodeRevision": rev,
+			"files":        batch,
+			"syncId":       syncID,
+			"batchIndex":   i,
+			"batchCount":   batchCount,
+			"isLast":       i == batchCount-1,
+		})
+		if err := c.writeWithDeadline(msg, writeDeadlineLong); err != nil {
+			log.Printf("full library sync batch %d/%d failed: %v", i+1, batchCount, err)
+			c.forceClose()
+			return
+		}
+
+		deadline := time.After(syncAckTimeout)
+		acked := false
+		for !acked {
+			select {
+			case ack := <-c.syncAckCh:
+				if ack.SyncID == syncID && ack.BatchIndex == i {
+					acked = true
+				}
+			case <-deadline:
+				log.Printf("full library sync batch %d/%d ACK timeout", i+1, batchCount)
+				c.forceClose()
+				return
+			case <-c.stopCh:
+				return
+			}
+		}
+
+		if (i+1)%10 == 0 || i == batchCount-1 {
+			log.Printf("Full library sync progress: batch %d/%d", i+1, batchCount)
+		}
+	}
+
+	log.Printf("Full library sync complete (%d files)", len(files))
 }
 
 func (c *Client) NotifySessionEnded(sessionID, reason string) {
@@ -316,6 +462,10 @@ func (c *Client) NotifySessionEnded(sessionID, reason string) {
 }
 
 func (c *Client) write(msg interface{}) error {
+	return c.writeWithDeadline(msg, writeDeadlineShort)
+}
+
+func (c *Client) writeWithDeadline(msg interface{}, deadline time.Duration) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	if c.conn == nil {
@@ -325,7 +475,7 @@ func (c *Client) write(msg interface{}) error {
 	if err != nil {
 		return err
 	}
-	_ = c.conn.SetWriteDeadline(time.Now().Add(15 * time.Second))
+	_ = c.conn.SetWriteDeadline(time.Now().Add(deadline))
 	return c.conn.WriteMessage(websocket.TextMessage, data)
 }
 

packages/protocol/src/index.ts

@@ -58,6 +58,18 @@ export interface LibraryEventPayload {
 export interface FullLibrarySyncPayload {
   nodeRevision: number;
   files: LibraryEvent["file"][];
+  /** Present when sync is split across multiple WebSocket messages */
+  syncId?: string;
+  batchIndex?: number;
+  batchCount?: number;
+  /** True on the final batch (or when sending a single unbatched sync) */
+  isLast?: boolean;
+}
+
+export interface FullLibrarySyncAckPayload {
+  accepted: boolean;
+  syncId?: string;
+  batchIndex?: number;
 }
 
 export interface RescanPayload {