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MassTransit–Change Exchange naming strategy

When you publish a message through MassTransit to RabbitMQ, a default naming strategy is used to create a corresponding exchange. The default naming convention is the fully qualified name of the message class, so if you have a class named HelloWorldMessage in a namespace MyCompany.Messages.V1, you’ll end up with an exchange named MyCompany.Messages.V1:HelloWorldMessage.

This is ok if you are running RabbitMQ locally(through Docker for example), but it gets quite annoying if you are publishing to a shared infrastructure during development. The problem is that you start receiving messages from other developers which makes debugging a lot more difficult.

To solve this problem I created a custom EntityNameFormatter that allows you to specify an extra environment setting that can be set to for example to a specific username. Doing this in MassTransit 5 is not that hard as you can set this for the whole MessageTopology(something that was not easily done in previous versions).

Here is the required code:

  • First, we have to create a custom formatter by implementing the IEntityFormatter interface(note that I’m passing in the original formatter):
  • Second, we have to apply this formatter. As I want to do this for all messages, I specify it on the MessageTopology setting:

Now we can specify a different name in our configuration and only receive the messages that we want.

Remark: You have to apply this code both on the send and receive side of your application

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