Don't block task queue for queued update task when there are longer running tasks executing

src/NzbDrone.Core/Download/ProcessMonitoredDownloadsCommand.cs

@@ -5,5 +5,7 @@ namespace NzbDrone.Core.Download
     public class ProcessMonitoredDownloadsCommand : Command
     {
         public override bool RequiresDiskAccess => true;
+
+        public override bool IsLongRunning => true;
     }
 }

src/NzbDrone.Core/Indexers/RssSyncCommand.cs

@@ -1,9 +1,11 @@
-using NzbDrone.Core.Messaging.Commands;
+using NzbDrone.Core.Messaging.Commands;
 
 namespace NzbDrone.Core.Indexers
 {
     public class RssSyncCommand : Command
     {
         public override bool SendUpdatesToClient => true;
+
+        public override bool IsLongRunning => true;
     }
 }

src/NzbDrone.Core/Messaging/Commands/Command.cs

@@ -26,6 +26,7 @@ namespace NzbDrone.Core.Messaging.Commands
         public virtual string CompletionMessage => "Completed";
         public virtual bool RequiresDiskAccess => false;
         public virtual bool IsExclusive => false;
+        public virtual bool IsLongRunning => false;
 
         public string Name { get; private set; }
         public DateTime? LastExecutionTime { get; set; }

src/NzbDrone.Core/Messaging/Commands/CommandQueue.cs

@@ -164,13 +164,24 @@ namespace NzbDrone.Core.Messaging.Commands
                                           {
                                               // If an executing command requires disk access don't return a command that
                                               // requires disk access. A lower priority or later queued task could be returned
-                                              // instead, but that will allow other tasks to execute whiule waiting for disk access.
+                                              // instead, but that will allow other tasks to execute while waiting for disk access.
                                               if (startedCommands.Any(x => x.Body.RequiresDiskAccess))
                                               {
                                                   return c.Status == CommandStatus.Queued &&
                                                          !c.Body.RequiresDiskAccess;
                                               }
 
+                                              // If an executing command is long running then skip any exclusive commands until
+                                              // they complete. A lower priority or later queued task could be returned
+                                              // instead, but that will allow other tasks to execute while waiting for exclusive
+                                              // execution.
+
+                                              if (startedCommands.Any(x => x.Body.IsLongRunning))
+                                              {
+                                                  return c.Status == CommandStatus.Queued &&
+                                                         !c.Body.IsExclusive;
+                                              }
+
                                               return c.Status == CommandStatus.Queued;
                                           })
                                           .OrderByDescending(c => c.Priority)

src/NzbDrone.Core/Tv/Commands/RefreshSeriesCommand.cs

@@ -20,5 +20,7 @@ namespace NzbDrone.Core.Tv.Commands
         public override bool SendUpdatesToClient => true;
 
         public override bool UpdateScheduledTask => !SeriesId.HasValue;
+
+        public override bool IsLongRunning => true;
     }
 }