From 880170637e79e63d9eea90a547cd74f3c7c6bd6e Mon Sep 17 00:00:00 2001
From: Taloth Saldono <Taloth@users.noreply.github.com>
Date: Sun, 3 May 2020 16:33:52 +0200
Subject: [PATCH] Fixed timing issue allowing multiple instances of the same
 command to be queued

---
 .../Messaging/Commands/CommandQueueManager.cs | 43 ++++++++++---------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/src/NzbDrone.Core/Messaging/Commands/CommandQueueManager.cs b/src/NzbDrone.Core/Messaging/Commands/CommandQueueManager.cs
index 9a65e5abf..92a10c940 100644
--- a/src/NzbDrone.Core/Messaging/Commands/CommandQueueManager.cs
+++ b/src/NzbDrone.Core/Messaging/Commands/CommandQueueManager.cs
@@ -100,32 +100,35 @@ namespace NzbDrone.Core.Messaging.Commands
             _logger.Trace("Publishing {0}", command.Name);
             _logger.Trace("Checking if command is queued or started: {0}", command.Name);
 
-            var existingCommands = QueuedOrStarted(command.Name);
-            var existing = existingCommands.SingleOrDefault(c => CommandEqualityComparer.Instance.Equals(c.Body, command));
-
-            if (existing != null)
+            lock (_commandQueue)
             {
-                _logger.Trace("Command is already in progress: {0}", command.Name);
+                var existingCommands = QueuedOrStarted(command.Name);
+                var existing = existingCommands.FirstOrDefault(c => CommandEqualityComparer.Instance.Equals(c.Body, command));
 
-                return existing;
-            }
+                if (existing != null)
+                {
+                    _logger.Trace("Command is already in progress: {0}", command.Name);
 
-            var commandModel = new CommandModel
-            {
-                Name = command.Name,
-                Body = command,
-                QueuedAt = DateTime.UtcNow,
-                Trigger = trigger,
-                Priority = priority,
-                Status = CommandStatus.Queued
-            };
+                    return existing;
+                }
+
+                var commandModel = new CommandModel
+                {
+                    Name = command.Name,
+                    Body = command,
+                    QueuedAt = DateTime.UtcNow,
+                    Trigger = trigger,
+                    Priority = priority,
+                    Status = CommandStatus.Queued
+                };
 
-            _logger.Trace("Inserting new command: {0}", commandModel.Name);
+                _logger.Trace("Inserting new command: {0}", commandModel.Name);
 
-            _repo.Insert(commandModel);
-            _commandQueue.Add(commandModel);
+                _repo.Insert(commandModel);
+                _commandQueue.Add(commandModel);
 
-            return commandModel;
+                return commandModel;
+            }
         }
 
         public CommandModel Push(string commandName, DateTime? lastExecutionTime, DateTime? lastStartTime, CommandPriority priority = CommandPriority.Normal, CommandTrigger trigger = CommandTrigger.Unspecified)