This section elaborates the automatic scaling of virtual services.
The Avi Load Balancer supports the automatic rebalancing of virtual services across the SE group based on the load levels experienced by each SE. Auto-rebalance can migrate or scale in/out virtual services to rebalance the load and, in a write-access cloud, this can also result in SEs being provisioned or de-provisioned if required.
Auto-rebalancing applies only if elastic HA has been selected for the SE group.
To configure auto-rebalancing for an SE group, see How to Configure Auto-rebalance Using NSX Advanced Load Balancer CLI
Scaling Out
The following are the steps to manually scale a virtual service out when Avi Load Balancer is operating in 'write access' mode:
Open the Virtual Service screen for the virtual service that you prefer to scale.
Hover the mouse pointer over the name of the virtual service to open the Virtual Service Quick Info popup message.
Click Scale Out button, to scale the Virtual Service out to an additional SE per click, up to four SEs.
If available, Avi Load Balancer will attempt to use an existing Service Engine. If none is available or matches reachability criteria, it may create a new SE.
In some environments, Avi Load Balancer may prompt for additional information to create a new Service Engine, such as additional IP addresses.
The prompt Currently Scaling Out displays the progress while the operation is taking place.
If virtual service scales out across multiple SEs, then each SE will independently perform server health monitoring to the pool’s servers.
Scaling out does not interrupt existing client connections.
Scaling out a virtual service can take around few seconds or few minutes. The scale out timing depends whether an additional SE exists or if a new SE with relevant network and disk speeds requirement must be created.
Scaling In
The following are the steps to manually scale in a virtual service in when Avi Load Balancer is operating in 'write access' mode:
Open the Virtual Service Details page for the virtual service that you prefer to scale.
Hover the pointer over the name of the virtual service to open the Virtual Service Quick Info popup message.
Click Scale In button, to open the Scale In popup window.
Select Service Engine to scale in. In other words, select the Service Engine that should be removed from supporting this virtual service.
Scale the virtual service by one Service Engine per SE selection, to a minimum of one Service Engine.
The prompt Currently scaling in displays the progress while the operation is taking place.
While Scaling In, existing connections take thirty seconds to complete. Remaining connections to the SE are closed and must restart.
Migrating
The Migrate option allows smooth migration from one Service Engine to another Service Engine. During this process, the primary SE will scale out to the new SE and begins to send it new connections. After thirty seconds, the old SE will be deprovisioned from supporting the virtual service.
Existing connections to the migration’s source Service Engine take thirty seconds to complete prior to the SE that is being deprovisioned for the virtual service. Remaining connections to the SE are closed and must restart.
