DC 5.1.0 4.5 Rabbit MQ

Short description around RabbitMQ usage in Digizuite. Important is to mention that you only want to change the RabbitMQ configuration if the customer specifically asks for it. 

RabbitMQ documentation: https://www.rabbitmq.com/documentation.html

NServiceBus RabbitMQ docs: https://docs.particular.net/transports/rabbitmq/

Details about Digizuite usage:

1. RabbitMQ is multi-tenant and can be structured in a concept called Virtual Hosts (https://www.rabbitmq.com/vhosts.html).
   
   
2. Digizuite utilize the Virtual Host concept to separate queues, exchanges and bindings between systems (this allows you to utilize an existing rabbit queue as an example so that systems on the same server can be separated on the same server and with a vhost in RabbitMQ for each of them systems).
   
   In the local Rabbit Management studio you can see all virtual hosts like this (localhost:15672):
   
   
   
   
3. For each vhost, we do create a publish queue and a number of subscription queues (right now there is a sub queue for DC and one for all other services such as audit and ai).
   
   
   
   
4. To exchange messages between the queues we use the conventional routing topology as per NServiceBus (https://docs.particular.net/transports/rabbitmq/routing-topology) rather than the Direct Routing with routing keys as I originally preferred. The reason is that conventional routing takes into consideration the inheritance aspect and therefore generating all exchanges for all interfaces as illustrated below:
   

Configuration

In almost all cases you won't have to do any configuration for RabbitMQ. The Digizuite installer will automatically install RabbitMQ and start it up on http://localhost:15672. This is default (connection string format: host=localhost;username=user;password=password;virtualhost=uniqueDbName).

If you wish to utilize other than localhost, it is important to create your own vhost with the RabbitCLI which is calculated based on the below. This is important because the services utilize this unique db name to connect to the correct vhost.

Furthermore, setting the right user privileges for that vhost is also crucial. As an examle, you would need to do the two following steps to create a vhost and set privileges with the RabbitMQ CLI:
rabbitmqctl.bat add_vhost $uniqueDbName 
rabbitmqctl.bat set_permissions -p $uniqueDbName guest ".*" ".*" ".*"

Next step would then be to construct and provide your host connection string for rabbit to the Digizuite DAM Center and Digizuite Core Services

1. A configurable rabbitmq connection string. Format is: host=localhost;username=guest;password=guest;virtualhost=uniqueDbName
2. This must be set in two places
   1. DAM Center app settings in web.config.
      

      <appSettings>
            <add key="rabbitMqConnectionString" value="host=localhost;username=guest;password=guest;virtualhost=uniqueDbName" />
            ......
      </appSettings>

   2. Digizuite Core services appsettings.json (DC Path/DigizuiteCore/appsettings.json): 
      

      "RabbitMQ": {        
           "ConnectionString": "host=localhost;username=user;password=password;virtualhost=uniqueDbName"
      }

Troubleshooting

One thing to be aware of after the installation has been done is the connections in rabbit. Always make sure that you see the following connections in the management ui.

You want to see these two connections (if more as below it is also okay):

*.dam.core.subscriber 

*.dam.core.webhost.subscriber

If you do not see these then you want to recycle the two highlighted:

If RabbitMQ is not running then please try to restart the service by running following commands in command prompt (in the library C:\Program Files\RabbitMQ Server\rabbitmq_server-3.7.8\sbin) :

1. rabbitmq-service.bat stop
2. rabbitmq-service.bat install
3. rabbitmq-plugins.bat enable rabbitmq_management
4. rabbitmq-service.bat start