Implemented skip parameter for export and shovel commands

Tapeti.Cmd/Verbs/ExportVerb.cs

@@ -23,6 +23,9 @@ namespace Tapeti.Cmd.Verbs
         [Option('r', "remove", HelpText = "If specified messages are acknowledged and removed from the queue. If not messages are kept.")]
         public bool RemoveMessages { get; set; }
 
+        [Option("skip", HelpText = "(Default: 0) Number of messages in the queue to skip. Useful if a previous non-removing export was interrupted.", Default = 0)]
+        public int Skip { get; set; }
+
         [Option('n', "maxcount", HelpText = "(Default: all) Maximum number of messages to retrieve from the queue.")]
         public int? MaxCount { get; set; }
     }
@@ -52,6 +55,11 @@ namespace Tapeti.Cmd.Verbs
             using var channel = connection.CreateModel();
 
             var totalCount = (int)channel.MessageCount(options.QueueName);
+
+            var skip = Math.Max(options.Skip, 0);
+            if (skip > 0)
+                totalCount -= Math.Min(skip, totalCount);
+            
             if (options.MaxCount.HasValue && options.MaxCount.Value < totalCount)
                 totalCount = options.MaxCount.Value;
 
@@ -67,24 +75,28 @@ namespace Tapeti.Cmd.Verbs
                         // No more messages on the queue
                         break;
 
-                    messageCount++;
-
-                    messageSerializer.Serialize(new Message
+                    if (skip > 0)
+                        skip--;
+                    else
                     {
-                        DeliveryTag = result.DeliveryTag,
-                        Redelivered = result.Redelivered,
-                        Exchange = result.Exchange,
-                        RoutingKey = result.RoutingKey,
-                        Queue = options.QueueName,
-                        Properties = result.BasicProperties,
-                        Body = result.Body.ToArray()
-                    });
+                        messageCount++;
 
-                    if (options.RemoveMessages)
-                        channel.BasicAck(result.DeliveryTag, false);
+                        messageSerializer.Serialize(new Message
+                        {
+                            DeliveryTag = result.DeliveryTag,
+                            Redelivered = result.Redelivered,
+                            Exchange = result.Exchange,
+                            RoutingKey = result.RoutingKey,
+                            Queue = options.QueueName,
+                            Properties = result.BasicProperties,
+                            Body = result.Body.ToArray()
+                        });
 
+                        if (options.RemoveMessages)
+                            channel.BasicAck(result.DeliveryTag, false);
 
-                    progressBar.Report(messageCount);
+                        progressBar.Report(messageCount);
+                    }
                 }
             }
 

Tapeti.Cmd/Verbs/ShovelVerb.cs

@@ -37,6 +37,9 @@ namespace Tapeti.Cmd.Verbs
         [Option("targetpassword", HelpText = "Password used to connect to the target RabbitMQ server. Defaults to the source password.")]
         public string TargetPassword { get; set; }
 
+        [Option("skip", HelpText = "(Default: 0) Number of messages in the queue to skip. Useful if a previous non-removing shovel was interrupted.", Default = 0)]
+        public int Skip { get; set; }
+
         [Option("maxrate", HelpText = "The maximum amount of messages per second to shovel.")]
         public int? MaxRate { get; set; }
 
@@ -93,6 +96,11 @@ namespace Tapeti.Cmd.Verbs
             var targetQueueName = !string.IsNullOrEmpty(options.TargetQueueName) ? options.TargetQueueName : options.QueueName;
 
             var totalCount = (int)sourceChannel.MessageCount(options.QueueName);
+
+            var skip = Math.Max(options.Skip, 0);
+            if (skip > 0)
+                totalCount -= Math.Min(skip, totalCount);
+
             if (options.MaxCount.HasValue && options.MaxCount.Value < totalCount)
                 totalCount = options.MaxCount.Value;
 
@@ -101,6 +109,18 @@ namespace Tapeti.Cmd.Verbs
 
             using (var progressBar = new ProgressBar(console, totalCount))
             {
+                // Perform the skips outside of the rate limiter
+                while (skip > 0 && !console.Cancelled)
+                {
+                    var result = sourceChannel.BasicGet(options.QueueName, false);
+                    if (result == null)
+                        // No more messages on the queue
+                        return;
+
+                    skip--;
+                }
+
+                
                 var hasMessage = true;
 
                 while (!console.Cancelled && hasMessage && (!options.MaxCount.HasValue || messageCount < options.MaxCount.Value))

docs/tapeticmd.rst

@@ -51,6 +51,9 @@ Fetches messages from a queue and writes them to disk.
 -r, --remove
   If specified messages are acknowledged and removed from the queue. If not messages are kept.
 
+--skip <count>
+  Number of messages in the input to skip. Useful if a previous non-removing export was interrupted.
+
 -n <count>, --maxcount <count>
   Maximum number of messages to retrieve from the queue. If not specified all messages are exported.
 
@@ -124,6 +127,9 @@ Reads messages from a queue and publishes them to another queue, optionally to a
 -r, --remove
   If specified messages are acknowledged and removed from the queue. If not messages are kept.
 
+--skip <count>
+  Number of messages in the input to skip. Useful if a previous non-removing shovel was interrupted.
+
 -n <count>, --maxcount <count>
   Maximum number of messages to retrieve from the queue. If not specified all messages are exported.