Rackspace Auto Scale FAQ



Pricing Questions

How much does the Rackspace Auto Scale service cost?

Auto Scale is available at no cost to Rackspace Cloud customers, although you do pay for the servers created by a scale-up until they are removed.

How do I know what actions are taken by Auto Scale on my behalf?

Some of the actions Auto Scale takes on your behalf are deferred; for example, when you set a schedule to create additional servers. Auto Scale will soon have an advanced audit log to track when Rackspace takes actions on your behalf. You will be able to access this through the history resource on the Auto Scale API endpoint.


Basics and Third Party Questions

What do I need to get started using Auto Scale?

Auto Scale works by horizontally scaling a particular tier of an application; for example, the web tier. You need to know which servers you want to scale. To get started, you need a server image that you have configured with all needed applications, and settings, and that is configured to be ready when the server is started. You can ensure your servers deploy fully ready for service by using various programs such as Chef, Puppet, and Salt.

Is authentication required for Auto Scale? 

Authentication is required to create a scaling group; you must send an x-auth-token header with most API requests. Authentication is not required to execute policies via anonymous webhooks.

How does Auto Scale integrate with image services or other automation services, such as Chef or Puppet?

Auto Scale is service agnostic and API based, so it works well with these services but does not explicitly integrate with them.

Does Auto Scale record the history of a scale action? 

Not currently. The history resource on the Auto Scale API endpoint will show scaling history, triggers, and user changes. It will be available in a future release.

Is there an easy path to migrate from other autoscaling products such as Rightscale? 

No. Your configurations cannot be migrated from other providers.


Server and Data Center Questions

Can I use Auto Scale across data centers?

No, you must create separate scaling groups for different data centers.

Can a server in ORD be added to a load balancer in the DFW data center, or use an image in DFW?

No, all the resources must be in the same data center. There is a different Auto Scale endpoint for each data center, and each endpoint orchestrates only within that data center. In the Auto Scale control panel, data centers are called Regions

When a server is automatically created, it is attached to a load balancer. Is it possible to create a server that is not attached to a load balancer?

Yes. A load balancer is not required as part of the launch configuration. However, you do need to configure how your servers get requests.

Can I suspend servers and restore them quickly to the same IP address?

No. Auto Scale does not suspend or restore servers. Newly created servers have different IP address.

Can I scale up servers in a particular order? For example, can I create a database server before creating a web server?

No. Auto Scale does not scale up servers or load balancers in a particular order.

What happens if I delete an Auto Scale server through Nova or through the Cloud Control Panel? 

Auto Scale currently does not track what happens to servers outside of the Auto Scale system. If a server is deleted outside of the system, Auto Scale considers that the server still exists. If you then try to delete the server through Auto Scale (for example, by scaling down), however, no problems should occur. A task for identifying and reacting to servers that have been deleted outside of Auto Scale is in the development backlog.

Does Auto Scale support First Generation Cloud Servers or images?

No, Auto Scale supports Next Generation Cloud Servers and Performance Cloud Servers.


Scaling Groups, Policies, and Configuration Questions

What is a scaling group?

A scaling group is a construct that contains the configuration for creating individual servers, has zero or more servers associated with it, and has one or more associated scaling policies that describe what actions to take when the policy is activated.

Can I create a scaling group with no servers in it?

Yes.

Do the servers that I'm going to automatically scale up have to be associated with a group? If so, why?

Yes. A scaling policy is associated with a specific group. All of the scaled-up servers are managed for health and monitoring in aggregate so they need to be a part of a group.

Can I add an existing server to an Auto Scale group?

No. Even if you add the autoscale-group-id metadata to the server, the Auto Scale back end service will not know the server belongs in the group. Auto Scale manages only servers created by Auto Scale.

Is there a limit to the number of servers I can have in a scaling group? 

There is no maximum number of servers in a scaling group.  However, a scaling group used with a cloud load balancer instance is limited to 50 servers per load balancer group and you may have overall Cloud Servers limits on the number of servers you are allowed to create without having your quota bumped up. If you reach cloud load balancer limits, Auto Scale will fail to add additional servers. If you are running up against limits with cloud load balancer instances, you should consider creating multiple scaling groups and a tree of load balancers to service requests or using RackConnect to use a higher capacity hardware load balancing solution. For more information on RackConnect, see How do I get started with RackConnect?

Can I have multiple load balancers in a scaling group?

If you need to scale beyond 25 servers with a cloud load balancer, we recommend creating multiple Auto Scale groups and creating a tree of load balancers.

Are monitoring rules for the entire scaling group or can I monitor specific servers in the scaling group? 

The checks and alarms are written and specified within the launch configuration and then submitted to the newly created entities. There are no specific rules for monitoring specific servers.

What are the different configuration parameters for scaling groups?

For information on the parameters used with the Auto Scale API, see the Auto Scale API Developer's Guide, Group Configurations and the Auto Scale API Developer's Guide, Launch Configuration.

For information on the parameters used with the Auto Scale Control Panel, see the Auto Scale User Guide, Creating Scaling Groups.

What are the different configuration parameters for scaling policies?

For information on the parameters used with the Auto Scale API, see the Auto Scale Developer's Guide, Create Policies.

For information on the parameters used with the Auto Scale Control Panel, see the

Auto Scale User Guide, Creating Policies.

Multiple scaling policies can be associated with the same scaling group. How is the "correct" policy selected when servers are generated?

The "handle" for each policy is defined by a construct called a webhook, which is a unique URL endpoint you call to invoke the policy execution.

How does Auto Scale moderate conflicting events?

Cooldown timers are built in to the scaling group and the individual scaling policies, so that you can prevent too many servers from being created or deleted too quickly.

What is the minimum amount of time you can set for a cooldown timer?

Zero seconds. We recommend having the group cooldown being around 5 minutes (300 seconds) by default.

What is the maximum limit you can set for a cooldown timer?

The maximum is 86400 seconds, equal to 24 hours.

Does Auto Scale drain connections on a node behind a load balancer as a service (LBaaS) before removing it from a pool?

No. The server is removed from the load balancer before the delete command is sent. At present, connections are not drained.

I got a 403 "Cannot execute policy - no change in servers" error when I tried to execute the policy. What does this mean?

One possibility is that you tried to scale up or down beyond the configured minimum or maximum value. As a result, no servers could be created or destroyed. The error message could also mean that you are trying to set the needed capacity equal to what Auto Scale thinks is already there.



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