Masstransit: Problem with MassTransit deserialization

[kninib12]

Okay so I have a problem with using MassTransit and it's deserialization.

We're publishing messages into a specific queue with RabbitMQ, which should then be further processed by our background services using MassTransit.

The string coming in through the queue looks as following

{

  "routingKey": "article.put",

  "responseQueue": {

    "exchange": "testexchange_gateway",

    "responseRoutingKey": "gatewayResponseQueue",

    "vhost": "testvhost"

  },

  "deviceProperties": {

    "deviceType": "DESKTOP",

    "deviceSize": {

      "width": 10,

      "height": 10

    },

    "javascriptEnabled": false

  },

  "action": "PUT",

  "transactionId": "62b6174d-04b7-4937-b617-4d04b70937b0",

  "contentType": "application/json",

  "body": "Testmessage published while running"

}

With the Contract looking like

```
public interface IMessage
{
string routingKey { get; set; }
ResponseQueue responseQueue { get; set; }
DeviceProperties deviceProperties { get; set; }
string action { get; set; }
string transactionId { get; set; }
string contentType { get; set; }
string body { get; set; }
}

public interface ResponseQueue
{
string exchange { get; set; }
string responseRoutingKey { get; set; }
string vhost { get; set; }
}

public interface DeviceProperties
{
string deviceType { get; set; }
DeviceSize deviceSize { get; set; }
bool javascriptEnabled { get; set; }

}

public interface DeviceSize
{
    int width { get; set; }
    int height { get; set; }
}

My problem now is, whenever I want to consume that message using MassTransit, I will get an error in my _error queue:

MT-Fault-ExceptionType: | System.ArgumentNullException
-- | --
Value cannot be null. Parameter name: source
at System.Linq.Enumerable.ToArrayTSource at MassTransit.Serialization.JsonConsumeContext..ctor(JsonSerializer deserializer, IObjectTypeDeserializer objectTypeDeserializer, ReceiveContext receiveContext, MessageEnvelope envelope) at MassTransit.Serialization.JsonMessageDeserializer.MassTransit.IMessageDeserializer.Deserialize(ReceiveContext receiveContext)

which I don't quite understand, as all values needed should be right there.

My consumer:

class ArticleGetConsumer : IConsumer
{
public Task Consume(ConsumeContext context)
{
var routingKey = context.Message.routingKey;
return Task.FromResult(0);
}
}
```

[phatboyg]

You need to wrap that message in an envelope. The format is detailed in the interoperability documentation:

http://masstransit-project.com/MassTransit/advanced/interoperability.html

[phatboyg]

Should look like this:

{
  "destinationAddress": "rabbitmq://localhost/input_queue",
  "headers": {},
  "messageType": [
    "urn:message:YourProject.Messages:IMessage"
    ],
  "message": {
    "routingKey": "article.put",
    "responseQueue": {
      "exchange": "testexchange_gateway",
      "responseRoutingKey": "gatewayResponseQueue",
      "vhost": "testvhost"
    },
    "deviceProperties": {
      "deviceType": "DESKTOP",
      "deviceSize": {
        "width": 10,
        "height": 10
      },
      "javascriptEnabled": false
    },
    "action": "PUT",
    "transactionId": "62b6174d-04b7-4937-b617-4d04b70937b0",
    "contentType": "application/json",
    "body": "Testmessage published while running"
  }
}

[kninib12]

Thanks for the quick answer, will try this tomorrow and report back!

[kninib12]

Okay so about the envelope, I get what it is for and why it's needed but, and I have searched thouroughly (and only found people saying that you need to wrap it in an envelope rather than how to do it), I can't seem to figure out as to how to properly wrap it. I could just set together the string manually but I don't think that's how it's meant to be, there has to be an easier way to do this.

How would I go about wraping it up?

[phatboyg]

Just look at how MT does it, throw the object into a wrapper object (envelope) before serializing it to JSON from your message producer: https://github.com/MassTransit/MassTransit/blob/develop/src/MassTransit/Serialization/JsonMessageSerializer.cs#L97

[phatboyg]

@kninib12 did you get it working?

[san7988]

Hello,

My issue is the same. The messages are published by python code which publishes the plain application level message with no mass transit specific attributes in the json.
Is there a way to still consume the messages from the queue, if published by a non mass transit type client? I get a serialization error :
StackTrace: | at System.Linq.Enumerable.ToArray[TSource](IEnumerable1 source) at MassTransit.Serialization.JsonConsumeContext..ctor(JsonSerializer deserializer, IObjectTypeDeserializer objectTypeDeserializer, ReceiveContext receiveContext, MessageEnvelope envelope) at MassTransit.Serialization.JsonMessageDeserializer.MassTransit.IMessageDeserializer.Deserialize(ReceiveContext receiveContext)

Thanks a lot

[phatboyg]

Yes, you can write your own deserializer - there isn't anything to fix in MT with this issue.

[san7988]

Yes, that would be one solution. We have decided to rather port the python components to c#.

[akaFalsh]

I am having the same issue.
I am trying to receive the message from rabbitmq were other application pushes data.
The data example is:

{"database":"test","table":"maxwell","type":"insert","ts":1582193439,"xid":6534,"commit":true,"data":{"id":1,"daemon":"Stanislaw Lem"}}

However I only see this error:

System.Runtime.Serialization.SerializationException: An exception occurred while deserializing the message envelope
---> System.ArgumentNullException: Value cannot be null. (Parameter 'source')
at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
at System.Linq.Enumerable.ToArrayTSource
at GreenPipes.Filters.RescueFilter2.GreenPipes.IFilter<TContext>.Send(TContext context, IPipe1 next)

The contract looks like this:

public class DatabaseChangeDto: IDatabaseChangeContract
{
    public string Database { get; set; }
    public string Table { get; set; }
    public string Type { get; set; }
    public DateTime Ts { get; set; }
    public long Xid { get; set; }
    public bool Commit { get; set; }
    public object Data { get; set; }
}

[derek-baker]

You need to wrap that message in an envelope. The format is detailed in the interoperability documentation:

http://masstransit-project.com/MassTransit/advanced/interoperability.html

Updated URL
https://masstransit-project.com/architecture/interoperability.html