Enabling Auto scale for better capacity and resiliency

Objectives

• Learn how to create an Auto scale template and group for the virtual server instance
• Learn how to enable the backend orchestration to add newly created virtual server instances to the backend server pool for the cloud load balancer

Architecture

Before you begin

This tutorial builds on the Deploying server pools and origins in a single MZR solution tutorial. If you don’t have an environment or need to rebuild your environment, use that tutorial to set it up.

You must remove any virtual server instances from the back-end server pool before you start this task. Auto scale requires an empty back-end server pool; an empty back-end pool has no servers that are attached to it.

Create Instance templates for virtual server instances

To create an Auto scale instance template for the virtual server instance, complete the following steps:

1. From the VPC overview page, scroll down to Auto scale and click Instance templates.

2. Click Create +.

3. In the New instance template:

   a. Enter vpc-region1-zone1-template for the instance template Name.

   b. Select vpc-region1 as the name for your VPC.

   c. Select a Resource group.

   d. Select Dallas 1 for the Location.

   e. Select the appropriate image for Image.

   If you select a stock image, you must do post-provisioning for the new virtual server instances to match the same functions as your current production web        server. If you select a custom image (for example, snapshot of the web server), you might have minimal or no post-provisioning.
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   f. Select jumphost-vsi for the SSH key.

   g. For Network interface:

   * Select *vpc-region1-zone1-subnet* as the **Subnet**.
   * Ensure *vpc-region1-webserver-sg* is the only item that is selected in **Security Groups**.
   

4. Click Create instance template.

Create Instance group

To create the Auto scale instance groups, complete the following steps:

1. From the VPC overview page, scroll down to Auto scale and click Instance groups.

2. Click Create +.

3. Under New instance group for VPC:

   a. Enter vpc-region1-zone1-group for the instance group Name.

   b. Select a Resource group.

   c. Optionally, add Tags to organize your resources.

   d. Select Dallas for your Region.

   e. Select vpc-region1-zone1-template for Select instance template.

   f. For Select subnets and load balancer:

   * Select *vpc-region1-zone1-subnet* for the **Subnet**.
   * Check **Use load balancer**.
   
       Selecting the **Use load balancer** option, enables the backend orchestration to add newly created virtual server instances to the backend server pool. When enabled, the backend orchestration informs the load balancer about any virtual servers that are created by the Auto scale feature and adds any created virtual servers to the backend pool servers. This selection is optional.
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   * Select *vpc-lb-region1-zone1* for **Load Balancer**.
   * Select *region1-zone1-pool* for **Pool**.
   * Enter the appropriate network port for **Application port**, *80* for HTTP or *443* for HTTPs.
   

   g. Select Dynamic for Choose scaling method.

   h. For Set instance group size:

   *	Enter *1* for **Minimum instances**
   *	Enter *3* for **Maximum instances**
   *	Enter *90* for **Aggregation window**
   *	Enter *120* for **Cooldown period**
   
   The minimum and maximum instance is the total of all instances (of current plus Auto scaled instances). In our case, since we only started with 1, then the minimum is 1. Also, when you are choosing the maximum number, make sure that the subnet has enough spare IP addresses to accommodate any new provisioned virtual server instances that are created by the Auto scale feature.
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   The instance group size values are for demonstrative purpose. No exact formula is used to determine these values as it depends on your business and application requirements. More often than not, it takes several test iterations to find the right values.
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   i. Click Add a policy under Create scaling policies:

   • Select Network out (Mbps) for Metric type.

   • Enter 1 for Average target utilization.

     Again, the resource and utilization values are target-based thresholds. The values that are used here are for demonstrative purpose only. Any values that you use must be based on your requirements and just like the instance group size, it might take a couple of test iterations to find the right values. If multiple scaling policies exist (for example, CPU and memory), then the membership calculation is done for each policy and the policy that has the higher membership wins.

4. Check that you agree that instances are created and reclaimed according to the instance group settings.

5. Click Create instance group.

Related Content

For more information about Auto scale, instance templates, and instance groups, see Creating an instance group for auto scaling.

For a detailed example, watch the video Don't let load be the reason for the 404 error