From 7e05804bcfc5f878fcfe9c7b0052a38ea1cba8a2 Mon Sep 17 00:00:00 2001
From: advplyr <advplyr@protonmail.com>
Date: Wed, 31 Aug 2022 17:39:02 -0500
Subject: [PATCH] Update:Lock file update scans from watcher and queue file
 updates so that 2 watcher scans never occur simultaneously #906

---
 server/scanner/Scanner.js | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/server/scanner/Scanner.js b/server/scanner/Scanner.js
index a67e0589..9a886cce 100644
--- a/server/scanner/Scanner.js
+++ b/server/scanner/Scanner.js
@@ -28,6 +28,10 @@ class Scanner {
     this.cancelLibraryScan = {}
     this.librariesScanning = []
 
+    // Watcher file update scan vars
+    this.pendingFileUpdatesToScan = []
+    this.scanningFilesChanged = false
+
     this.bookFinder = new BookFinder()
   }
 
@@ -494,7 +498,16 @@ class Scanner {
   }
 
   async scanFilesChanged(fileUpdates) {
-    if (!fileUpdates.length) return
+    if (!fileUpdates || !fileUpdates.length) return
+
+    // If already scanning files from watcher then add these updates to queue
+    if (this.scanningFilesChanged) {
+      this.pendingFileUpdatesToScan.push(fileUpdates)
+      Logger.debug(`[Scanner] Already scanning files from watcher - file updates pushed to queue (size ${this.pendingFileUpdatesToScan.length})`)
+      return
+    }
+    this.scanningFilesChanged = true
+
     // files grouped by folder
     var folderGroups = this.getFileUpdatesGrouped(fileUpdates)
 
@@ -520,6 +533,13 @@ class Scanner {
       var folderScanResults = await this.scanFolderUpdates(library, folder, fileUpdateGroup)
       Logger.debug(`[Scanner] Folder scan results`, folderScanResults)
     }
+
+    this.scanningFilesChanged = false
+
+    if (this.pendingFileUpdatesToScan.length) {
+      Logger.debug(`[Scanner] File updates finished scanning with more updates in queue (${this.pendingFileUpdatesToScan.length})`)
+      this.scanFilesChanged(this.pendingFileUpdatesToScan.shift())
+    }
   }
 
   async scanFolderUpdates(library, folder, fileUpdateGroup) {