5.1.2. Horizontal scaling#
By horizontal scaling, we mean that you can run multiple instances of the vantage6 server simultaneously to handle a high workload. This is useful when a single machine running the server is no longer sufficient to handle all requests.
How it works#
Horizontal scaling with vantage6 can be done using a RabbitMQ server. RabbitMQ is a widely used message broker. Below, we will first explain how we use RabbitMQ, and then discuss the implementation.
The websocket connection between server and nodes is used to process various changes in the network’s state. For example, a node can create a new (sub)task for the other nodes in the collaboration. The server then communicates these tasks via the socket connection. Now, if we use multiple instances of the central server, different nodes in the same collaboration may connect to different instances, and then, the server would not be able to deliver the new task properly. This is where RabbitMQ comes in.
When RabbitMQ is enabled, the websocket messages are directed over the RabbitMQ message queue, and delivered to the nodes regardless of which server instance they are connected to. The RabbitMQ service thus helps to ensure that all websocket events are still communicated properly to all involved parties.
How to use#
If you use multiple server instances, you should always connect them to the same
RabbitMQ instance. You can achieve this by adding your RabbitMQ server when you
create a new server with
vserver new, or you can add it later to your
server configuration file as follows:
$user is the username,
$password is the password,
$host is the URL where your RabbitMQ service is running,
the queue’s port (which is 5672 if you are using the RabbitMQ Docker image), and
$vhost is the name of your
virtual host (you could e.g. run one
instance group per vhost).
If you are running a test server with
vserver start, a RabbitMQ docker
container will be started automatically for you. This docker container contains
a management interface which will be available on port 15672.
For deploying a production server, there are several options to run RabbitMQ. For instance, you can install RabbitMQ on Azure <https://www.golinuxcloud.com/install-rabbitmq-on-azure/>_.