Horizontal scaling of VMs enables users to configure an automatic response to changing demands for resources. To scale out, the platform clones the base VM and deploys the clones. To scale in, Abiquo will delete clone machines but it will just undeploy the base machine. Scaling operations are subject to all standard Abiquo constraints, such as privileges and allocation limits.

To use autoscaling do these steps:

1. Create a base VM, which can be deployed or undeployed
2. Define a scaling group with rules for scaling the VM
3. Create an action plan with scaling actions for the VM. Create triggers for the action plan, which are either monitoring alerts for virtual appliances or schedules for planned scaling

Create a scaling group

Before you begin:

1. Configure the base VM
2. Ensure that you have enough resources in your virtual datacenter to deploy up to the maximum number of cloned VMs, especially IP addresses

To create a scaling group:

1. In virtual appliance view, select the virtual machine, and from the menu on the virtual machine icon, select the Create scaling group option
2. Enter the scaling parameters and rules
3. Click Save

When you save the scaling group, Abiquo will mark the virtual machine icon with the scaling group symbol and display the scaling group name. If necessary, Abiquo will create clones of the base machine and deploy them in order to reach the minimum size. The number in the bottom right-hand corner of the icon is the number of running virtual machines in the scaling group, including the base machine.

To open the scaling group and check its parameters, click the scaling gruop symbol in the top right-hand corner of the VM icon.

Triggering autoscaling

To trigger autoscaling operations, create an action plan for the virtual machine with the scaling group, and then create triggers to run the action plan. See Manage action plans and triggers. When scaling, the platform will search for a rule that is valid for the specific time range, or for a default rule. It will create or delete/undeploy the number of VMs in the rule, then wait for the cooldown period before accepting another scaling request. 

To scale out, the platform does not deploy VMs that are undeployed in the scaling group. To clone the base virtual machine, the platform will do the following steps:

1. Create disks using the following:
   
   1. Copies of content of disks from the VM template
   2. Empty disks or volumes for each additional disk used in the VM
   3. Disk controllers used in the VM
2. Apply ALL configuration used in the VM, for example:
   
   1. CPU and RAM
   2. Network connections of the same type (e.g. private network)
   3. Assignment of firewall policies and attachment to load balancers
   4. Chef recipes, backups, cloud-init, variables, and so on
   5. Metrics. The group of metrics from clone machines and the base machine (if it is deployed) can activate alarms in the base machine, even if it is not deploye
   6. Exception – Alarms: the scaling group has only one alarm in the base machine

To scale in,  Abiquo currently selects the virtual machines to delete or undeploy using first in, first out (FIFO). The platform deletes and undeploys VMs without requesting user confirmation when there are disks that are not stored in the Apps library (ISO configuration drive or additional hard disk). 

Perform maintenance on the scaling group

Maintenance mode temporarily disables autoscaling and enables you to make changes to your VMs (deploy, undeploy, delete etc.) and edit the scaling group. Note that you cannot delete the base VM without deleting the scaling group. Also you cannot create alarms for cloned VMs that are part of a scaling group, because the scaling group alarms are in the base VM. When you leave maintenance mode, Abiquo will apply your modifications to the scaling group, e.g. adding new rules. Then Abiquo will adjust the number of virtual machines in the group to within the minimum and maximum size range.

• To put the scaling group in maintenance mode, click the "cog" maintenance button or trigger an action plan with the action "Scaling group: start maintenance mode"
• To leave maintenance mode, click the "cog" maintenance button again or trigger an action plan with the action "Scaling group: end maintenance mode".

Delete a scaling group

When you delete a scaling group, Abiquo will place all the VMs in the virtual appliance as regular VMs and the scaling group constraints will no longer exist. To delete a scaling group, first put it into maintenance mode, then click the delete button.