This article defines the following common Auto Scale terms:

Agent

A monitoring daemon that resides on the server you are monitoring. The agent gathers metrics based on agent checks and pushes them to Rackspace Monitoring.

Agent token

An authentication token used to identify the agent when it communicates with Rackspace Monitoring.

Alarm

A mechanism that contains a set of rules that determine when a notification is triggered.

Authentication

The act or process of confirming the identity of a user or the truth of a claim. The authentication service confirms that the user who claims to be making an incoming request is actually the one making the request. The service does this by validating a set of claims that the user makes. These claims are initially in the form of a set of credentials. After initial confirmation based on credentials, the authentication service issues a token to the user. When making subsequent requests, the user can provide the token as evidence that the service has already authenticated the user’s identity.

Check

A definition that explicitly specifies how you want to monitor an entity.

Collector

Software that collects data from the monitoring zone. The collector maps directly to an individual computer or a virtual machine.

Convergence

The act of Auto Scale adding or removing enough servers to satisfy the needed capacity.

Convergence Delta

The change in the number of servers that the system makes when a scaling policy is executed. For example, if the convergence delta is 2, then the system adds two servers. If it is -10, the system removes ten servers.

Cooldown

See Group cooldown and Policy cooldown.

Entity

A resource that you want to monitor. Some examples are a server, a website, or a service.

Flavor

A resource configuration for a server. Each flavor is a unique combination of disk, memory, vCPUs, and network bandwidth.

Group cooldown

The length of time that must pass before a scaling group can be scaled up or down again. The cooldown prevents events from triggering a new policy execution before server builds initiated by a previous policy execution complete.

Health monitor

A configurable feature of each load balancer. A health monitor is used to determine whether a back-end node is usable for processing a request. The load balancing service currently supports active health monitoring.

Image

A collection of files for a specific operating system (OS) that you use to create or rebuild a server. Rackspace provides prebuilt images. You can also create custom images from servers that you have launched. Use custom images for data backups or as golden images for additional servers.

Launch configuration

A configuration that contains the necessary details for adding and removing servers from a scaling group in the Rackspace Auto Scale API. The launchConfiguration object specifies whether you are creating a server or a load balancer and the necessary details about the configuration.

Load balancer

A logical device that belongs to a cloud account. You can use a load balancer to distribute workloads between multiple back-end systems or services, based on the configuration criteria.

Node

A back-end device that provides a service on a specified IP and port.

Notification

An informational message that is sent to one or more addresses when an alarm is triggered.

Policy cooldown

The length of time that must pass before a policy can be executed again. The purpose is to allow for a fast scale-up and a slow-scale down of servers.

Scaling

The process of adding or reducing capacity in response to changes in workload.

Scaling group

A set of identical servers, and optionally a load balancer, that can scale up and down in response to load, as defined by the scaling policy and bound by the scaling-group configuration.

Scaling policy

A policy that specifies how much capacity (that is, cloud servers) to add or reduce. A schedule-based scaling policy also specifies when this should happen. An event-based scaling policy relies on alerts that trigger webhooks.

Session persistence

A feature of the load balancing service that attempts to force subsequent connections to a service to be redirected to the same node as long as the node is online.

Server

A computer that provides explicit services to the client software running on its system. A server is a virtual machine (VM) instance in the Cloud Servers environment. To create a server, you must specify a name, flavor reference, and image reference.

Server image

See Image.

Virtual IP

An Internet Protocol (IP) address that you configure on the load balancer. Clients use the virtual IP to connect to a load balanced service. Based on its configuration, the load balancer distributes incoming connections to back-end nodes.

Webhook

A URL that can activate a specific (scale-up or scale-down) policy for a scaling group without requiring authentication.