With autoscaling we refer to the system's ability to automatically adjust session host instances' resources (RAM & CPU) according to number of users created in the environment. Autoscale can also automatically create new session host instance when you reach your maximum number of users per server and it can apply your custom image to configure the new server. 

Note: The resources (RAM, CPU) can also be adjusted manually through itopia VM Instances module if you disable the autoscale. Make sure you disable the autoscale before manually changing RAM and CPU.
Autoscaling settings can be fully customized according to your preferences and you can have different autoscaling settings per RD Collection.
Once configured, the system will automatically add or remove resources and /or VM instances from the collection based on increases or decreases in number of created users.

The following information explains how the default formula works to assign your resources:

Default VM instances:

PDC server (Primary domain controller): 1 CPU, 5.5 GB RAM, 50 GB storage

FBU/USS VM instances

0-7 users: 2 CPU, 7.5 GB RAM 

8 -15 users 4 CPU, 15 GB RAM

16 – 25 users: 4 CPU, 26 GB RAM

26 users and more: new USS VM instance (session host) will be created with 4 CPU and 13 GB RAM on both VM instances

VM instances that are not managed by autoscale:

BDC/SDC (Backup/Secondary domain controller): 1 CPU, 5.5 GB RAM
RDG1 server (RDS Gateway): 1 CPU, 3.8 GB RAM
RDG2 server (Redundant Gateway): 1 CPU, 3.8 GB RAM
BRK server (Dedicated Broker): 1 CPU, 3.8 GB RAM
FSB (Dedicated file server/Broker): 1 CPU, 3.8 GB RAM

Configure Autoscaling 

If you have Professional plan with itopia, you can configure autoscaling from Cloud Desktops section > RD Collections. The configuration becomes available once the deployment is launched to cloud. 

Go to Cloud Desktops section and select RD Collections

Select the collection and choose Edit

If you have multi-region deployment, first select the region you will be changing the settings for. Then continue to the next step.

If you decide to customize the autoscaling settings, start defining the maximum number of users per server.

When the amount of created users exceeds your number, new user session server will be created.

Note: the system takes into account all the users created in the itopia CAS - Users module, not the users that are logged in.

Then continue by specifying your requirements on the right. You can start deleting the default configuration to set up your own.

Server specifics: Here you can determine the resources for the VM instance depending on the number of users.
First choose the min and max number of users per resource setup (always start with 0 for the first entry), then select a Machine type. To add the setting, click on the green + sign. 

The setting will be displayed in the list on the right. Continue the same way till the max number of users per server is reached like in the below example:

Continue below to select an Image for your autoscaling settings.

Using Custom Images to Configure Autoscaling

You can create your custom images with installed applications and use them to configure your session host servers automatically. You will save time that you'd normally spend installing all the new applications in the newly created session host servers.

You have 2 options when using images for autoscaling:

  1. Use your custom image to create new session host VM instances. You can keep your current session host configuration and all the new session hosts that will be created by autoscale will be set up using your custom image.
  2. You can use your image to re-configure all your existing session host servers

Learn more about creating a custom image following this guide.

Once you created your custom image, go to Cloud Desktops > RD Collections.

Select the collection for the dedicated VM user.

Go to Image drop down and select the custom image you created. It will be listed under "Custom"
You can also select any of the standard images Google offers

Then decide if you'd like to apply the image to all your session host servers or just the new session hosts.
If you'd only like the image to apply to the session host servers created from now on, leave the option below unchecked:

If you checked the option "Apply to existing USS", the system will delete your existing session host servers and create them again using your image.

Important: Please note that if you selected the image to reconfigure all your existing session host servers, the system will not apply the image to the session host servers that are combined with file server role ( FBU server). That means that if the image has a different OS version than the initial session host set up, there can be difference in the end user experience.

Once you confirm your configuration, select the time when the changes should be applied. If you select Force update option, the changes will be applied immediately and your servers will reboot.

Click Save.

Note1: After using an image to create new session host servers, make sure to reconfigure the app restrictions in itopia CAS so the settings are applied to the new servers.

Note2: The image that you selected for the autoscale will also be used to create any new 1:1 servers when the option is enabled for a user. Learn more here.

What happens when autoscaling is triggered?

As previously mentioned, the system scales your resources based on user count. The autoscale is triggered as you add or remove users in Users module or whenever you change the autoscaling settings in the portal. 

Whenever the VM instance resources need to be updated, you get an alert in the portal that the VM instances will need to reboot to update. The system asks you to select when you want the resources to be reconfigured (servers rebooted). You can force the change with "Force update" option or schedule it to a specific day and time. 

In case the resource change includes new session host creation, the system will spin up a new VM instance and create a task for every application that must be installed on the newly created VM. At this moment end user logins are disabled to the new VM instance.

Note: The new session host will be created in the same datacenter region but different zone (e.g. if you deployed in US- East1-b, the new session host can be created in US-East1-c). The reason is to balance the session hosts.

You need to install all the applications on the VM instance and mark all the installation tasks as complete in itopia for the end user logins to be allowed in the VM instance. In other words, once you complete all the installation tasks, system allows logins to the server and scales the other VM instances resources according to your selected schedule (reboot needed). If you selected "Force update" option, the changes will be done right away.

If you chose a custom image for autoscale, you still get the tasks to install applications but you don't have to install those that are already on the image. The tasks in this case are just a way of confirming the apps were installed.

Low GCP resource quota preventing the Autoscale process from launching

The below changes are the events that can trigger the autoscale process (reconfiguration of your resources):

  • You change the autoscaling configuration
  • Adding/ removing a user in Users module

If there's any obstacle like low IP quota (static IP, CPU, GPU) that prevents our systems from launching the autoscale process, the above changes will fail. In other words, the system will not save your autoscale changes nor add/ remove a user. You will receive an error message advising you to increase your quota in GCP.

Once you increase the quota in Google Cloud, you can add/ remove the user or change the autoscaling settings.

How to disable Autoscaling

You can disable the autoscaling anytime with the button on the top left. 

IMPORTANT: When autoscale is disabled, you have to manage the session host resources (RAM, CPU) manually from VM Instances module. You will not be able to automatically add/remove session host servers as your user count changes.

Autoscaling failed creating a new VM instance

In case the autoscale process fails for other reason than low GCP resource quota, you will receive a notification under the bell icon in top right. Feel free to contact support if you notice such log.

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