Impact of the new "Availability Zone Aware routing" feature in Gorouter for TAS 6.x on Load Balancing

Products

• VMware Tanzu Application Service

Issue/Introduction

This KB article goes over the potential impact that the new Availability Zone Aware routing feature introduced in TAS 6.x. 

The description of this new feature:

Resolution

Gorouter will still do round-robin (connection), however it will initially only consider the applications within its own AZ when doing the calculation. However, it was found that this could potentially result in uneven application load balancing: 

 

The impact would also depend on the number of gorouters present in each AZ as well as how many application instances there are in an AZ. If each AZ has the same number of Gorouters, then this issue may not manifest.

To minimize uneven traffic, it is recommended to have an even number of gorouters scaled on the platform per the number of AZs. So in the example above, we should ideally have 2 Gorouters in AZ1 and 2 Gorouters in AZ2.