From fb025d9f685660c9b28f59632a65f1431c6d145b Mon Sep 17 00:00:00 2001
From: Qstick <qstick@gmail.com>
Date: Sun, 20 Aug 2023 16:46:55 -0500
Subject: [PATCH] Switch to Parallel.ForEach for list processing with
 MaxParallelism

(cherry picked from commit 0f93e04186f24abdb0cf0b3ba6a3505fda834e06)
---
 .../FetchAndParseImportListService.cs         | 79 +++++++------------
 1 file changed, 29 insertions(+), 50 deletions(-)

diff --git a/src/NzbDrone.Core/ImportLists/FetchAndParseImportListService.cs b/src/NzbDrone.Core/ImportLists/FetchAndParseImportListService.cs
index 382b76727..e1af65e79 100644
--- a/src/NzbDrone.Core/ImportLists/FetchAndParseImportListService.cs
+++ b/src/NzbDrone.Core/ImportLists/FetchAndParseImportListService.cs
@@ -3,7 +3,6 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using NLog;
-using NzbDrone.Common.TPL;
 using NzbDrone.Core.Parser.Model;
 
 namespace NzbDrone.Core.ImportLists
@@ -41,10 +40,7 @@ namespace NzbDrone.Core.ImportLists
 
             _logger.Debug("Available import lists {0}", importLists.Count);
 
-            var taskList = new List<Task>();
-            var taskFactory = new TaskFactory(TaskCreationOptions.LongRunning, TaskContinuationOptions.None);
-
-            foreach (var importList in importLists)
+            Parallel.ForEach(importLists, new ParallelOptions { MaxDegreeOfParallelism = 5 }, importList =>
             {
                 var importListLocal = importList;
                 var importListStatus = _importListStatusService.GetLastSyncListInfo(importListLocal.Definition.Id);
@@ -56,35 +52,28 @@ namespace NzbDrone.Core.ImportLists
                     if (DateTime.UtcNow < importListNextSync)
                     {
                         _logger.Trace("Skipping refresh of Import List {0} ({1}) due to minimum refresh interval. Next sync after {2}", importList.Name, importListLocal.Definition.Name, importListNextSync);
-                        continue;
+                        return;
                     }
                 }
 
-                var task = taskFactory.StartNew(() =>
-                     {
-                         try
-                         {
-                             var importListReports = importListLocal.Fetch();
+                try
+                {
+                    var importListReports = importListLocal.Fetch();
 
-                             lock (result)
-                             {
-                                 _logger.Debug("Found {0} reports from {1} ({2})", importListReports.Count, importList.Name, importListLocal.Definition.Name);
+                    lock (result)
+                    {
+                        _logger.Debug("Found {0} reports from {1} ({2})", importListReports.Count, importList.Name, importListLocal.Definition.Name);
 
-                                 result.AddRange(importListReports);
-                             }
+                        result.AddRange(importListReports);
+                    }
 
-                             _importListStatusService.UpdateListSyncStatus(importList.Definition.Id);
-                         }
-                         catch (Exception e)
-                         {
-                             _logger.Error(e, "Error during Import List Sync of {0} ({1})", importList.Name, importListLocal.Definition.Name);
-                         }
-                     }).LogExceptions();
-
-                taskList.Add(task);
-            }
-
-            Task.WaitAll(taskList.ToArray());
+                    _importListStatusService.UpdateListSyncStatus(importList.Definition.Id);
+                }
+                catch (Exception e)
+                {
+                    _logger.Error(e, "Error during Import List Sync of {0} ({1})", importList.Name, importListLocal.Definition.Name);
+                }
+            });
 
             result = result.DistinctBy(r => new { r.Artist, r.Album }).ToList();
 
@@ -105,35 +94,25 @@ namespace NzbDrone.Core.ImportLists
                 return result;
             }
 
-            var taskList = new List<Task>();
-            var taskFactory = new TaskFactory(TaskCreationOptions.LongRunning, TaskContinuationOptions.None);
-
             var importListLocal = importList;
 
-            var task = taskFactory.StartNew(() =>
+            try
             {
-                try
+                var importListReports = importListLocal.Fetch();
+
+                lock (result)
                 {
-                    var importListReports = importListLocal.Fetch();
+                    _logger.Debug("Found {0} reports from {1} ({2})", importListReports.Count, importList.Name, importListLocal.Definition.Name);
 
-                    lock (result)
-                    {
-                        _logger.Debug("Found {0} reports from {1} ({2})", importListReports.Count, importList.Name, importListLocal.Definition.Name);
-
-                        result.AddRange(importListReports);
-                    }
-
-                    _importListStatusService.UpdateListSyncStatus(importList.Definition.Id);
+                    result.AddRange(importListReports);
                 }
-                catch (Exception e)
-                {
-                    _logger.Error(e, "Error during Import List Sync of {0} ({1})", importList.Name, importListLocal.Definition.Name);
-                }
-            }).LogExceptions();
 
-            taskList.Add(task);
-
-            Task.WaitAll(taskList.ToArray());
+                _importListStatusService.UpdateListSyncStatus(importList.Definition.Id);
+            }
+            catch (Exception e)
+            {
+                _logger.Error(e, "Error during Import List Sync of {0} ({1})", importList.Name, importListLocal.Definition.Name);
+            }
 
             result = result.DistinctBy(r => new { r.Artist, r.Album }).ToList();