Multi Level Cluster

What is Multi-Level Cluster?

A cluster which has different regions is called Multi-Level Cluster where each region has its own origin for a stream. Ant Media Server can be scaled in different physical locations. You can set the node group parameter of the servers to create regions. Separating the nodes into regions based on their physical location has some advantages in performance and data-transfer. Because each region will have their own origin node for a stream, the edges in a region will pull the stream from the origin of their region.

How does it work?

Let's clarify the the case with an example scenario. We have two scenarios

1. Publisher & Players in the same cluster
2. Publisher & Players in the different clusters

Let's remember the traditional scenario

Publisher & Players in the same cluster

1. Publisher starts a stream and it is assigned to the Origin1 instance in the Region1
2. Player1 who is close to Region1 instance requests to play the stream.
3. Player1 is assigned to Edge11 instance to receive the stream in Region1
4. Since the Origin1 is the origin of the stream, Edge11 will pull stream from Origin1.

Publisher & Players in the different clusters

1. Player2 who is close to Region2 requests to play the stream.
2. Player2 is assigned to Edge21 instance in Region2
3. Edge21checks the origin of the stream.
   • Since there is no origin instance in Region2 to play the stream. It assigns itself as the secondary origin for that stream in Region2.
   • Edge21 pulls the stream from the Origin1 (main origin) in Region1.
   • Edge21 sends the stream to Player2.
4. Player3 who is close to Region2 requests to play the stream.
5. Player3 is assigned to Edge22 in Region2.
6. Edge22 checks the origin of the stream. Since Edge21 is a secondary origin for the stream in the Region2, it pulls the stream from Edge21 and serves to Player3.

In short, each stream is distributed from single node in each region even if they are in different regions.

How to configure Multi-Level Cluster?

You can set the node group (or region) of a server by adding nodeGroup=GROUP_NAME in conf/red5.properties file. Make sure that the instances running in the same region should have the same nodeGroup value

Keep in mind that you should configure the Load Balancer to forward Publish and Play requests to the best region. If you have a global cluster in different geolocations, you should have a Load Balancer like Route53.