ikolomiyets / TodoApi

A sample application illustrating the use of the RabbitMQ.client library in .NET Core API to process requests asynchronously.

TodoApi

This is a sample API that illustrates the use of the RabbitMQ library in processing API requests asynchronously. There are four standard Rest API endpoints available:

• GET /api/todoitems - retrieving all todo items
• GET /api/todoitems/ - retrieving a todo item, identified by id
• POST /api/todoitems - creates a new todo item
• PUT /api/todoitems/ - updates a todo item, identified by id
• DELETE /api/todoitems/ - deletes a todo item, identified by id

Todo items are stored in the in-memory database.

The format of the todo item is:

Name	Type	Description
id	int	Todo item id
name	string	Todo item name
isComplete	boolean	Flag indicating if item is complete

For example:

{
  "id": 3,
  "name": "walk dog",
  "isComplete": true
}

When sending a new object to the POST endpoint, id should be omitted, for example:

{
  "name": "walk dog",
  "isComplete": true
}

Two of the requests are processed asynchronously: POST and DELETE. The POST controller also illustrates technique how to get response from the asynchronous consumer.

The idea is to create a temporary queue, in this case we use the same prefix as the others and randomly generated UUID and bind the queue to the same routing key. When controller sends the message to the consumer for processing, it then tries to get the message from the temporary queue. If attempts fail after number of seconds controller just returns the original request. If it succeeds in receiving the message back, it returns the todo item with the newly assigned id. Then, temporary queue is deleted.

The temporary queue has the TTL assigned to it, identified by the rabbit__ttl environment variable (or rabbit.Ttl property). The ttl is the queue time to live in milliseconds. If it is not deleted after TTL milliseconds, the queue will be deleted automatically.

RabbitMQ configuration

There are number of the RabbitMQ configuration properties that could be set in appsettings.json or via environment variables: All properties are set in the "rabbit" object.

Name	Environment Variable	Default Value	Description
HostName	rabbit__hostname	localhot	The RabbitMQ host name
Port	rabbit__port	5672	The RabbitMQ port
VHost	rabbit__vhost	/	The virtual host
UserName	rabbit__username	N/A	The RabbitMQ username
Password	rabbit__password	N/A	The above user password
Ttl	rabbit__ttl	60	The temporary queue time-to-live in seconds
RetrieveTimeout	rabbit_retrievetimeout	10	Time in seconds which controller waits until giving up the attempts to get response from the consumer
Prefix	rabbit_prefix	Todo	A prefix that will be added to all the echange, queue and routing keys names.

For example

{
  "rabbit": {
      "UserName": "todo",
      "Password": "password",
      "Hostname": "localhost"
  }
}

Prefix

Prefix is used to fine tune access for the application's RabbitMQ user. When user is created, they have to be granted all Configure, Write and Read access to the following regex: .*

For example: Todo.*. Then, user will be able to create all necessary exchanges, queues and bindings.

If we would like to deploy another instance of the application that is using the same RabbitMQ instance, we just need to change prefix and assign correct rights to the user that handles the second instance. In this case, both instances will use their own exchanges and own sets of queues.