fix: optimize polling parallelism and resolve redundant SABnzbd requests (fixes #35, fixes #36)

server/utils/downloadClients.js

@@ -149,23 +149,42 @@ class DownloadClientRegistry {
     const clients = this.getAllClients();
     const result = {};
 
-    // Group by client type
+    if (clients.length === 0) {
+      return result;
+    }
+
+    // Reset fallback flags for qBittorrent clients
     for (const client of clients) {
+      if (client.resetFallbackFlag) {
+        client.resetFallbackFlag();
+      }
+    }
+
+    // Fetch downloads from all clients in parallel
+    const results = await Promise.allSettled(
+      clients.map(async (client) => {
+        const downloads = await client.getActiveDownloads();
+        return {
+          type: client.getClientType(),
+          downloads
+        };
+      })
+    );
+
+    // Group by client type
+    for (let i = 0; i < clients.length; i++) {
+      const client = clients[i];
       const type = client.getClientType();
       if (!result[type]) {
         result[type] = [];
       }
 
-      // Reset fallback flags for qBittorrent clients
-      if (client.resetFallbackFlag) {
-        client.resetFallbackFlag();
-      }
-
-      try {
-        const downloads = await client.getActiveDownloads();
-        result[type].push(...downloads);
-      } catch (error) {
-        logToFile(`[DownloadClientRegistry] Error fetching from ${client.name}: ${error.message}`);
+      const res = results[i];
+      if (res.status === 'fulfilled' && res.value) {
+        result[type].push(...res.value.downloads);
+      } else {
+        const errorMsg = res.status === 'rejected' ? res.reason?.message : 'Unknown error';
+        logToFile(`[DownloadClientRegistry] Error fetching from ${client.name}: ${errorMsg}`);
       }
     }