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Market Scoring and Managing Interruptions

This article explains how Elastigroup manages the replacement of instances in spot markets with predicted interruptions to ensure that your workloads remain available, as well as how Elastigroup handles the process of ranking (scoring) spot instance markets.

How Interruption Management Works​

  1. Elastigroup detects an unstable spot market, based on patterns in past interruptions and real-time market analytics.
  2. If other spot markets are available, a new instance is launched in the least expensive market and the old instance is drained and terminated.
  3. If other spot markets aren't available, Elastigroup activates the Fallback to On-Demand process in which an On-Demand instance is launched and the old instance is drained and terminated.

Spot Instance Replacement​

The flow chart below shows an overview of how the spot instance replacement takes place. The process repeats continuously.

Fix Strategy​

Elastigroup performs the following fix strategy processes based on your revert to Spot setting:

Revert to Spot​

Whenever the Spot Instance Replacement flow (described above) requires a fallback to an on-demand instance, the Fix Strategy flow is triggered. Elastigroup continuously monitors Spot markets to identify available markets for the workloads that are running on on-demand instances. When a Spot market becomes available, a new Spot instance is launched, and the old on-demand instance is drained and terminated. The revert to Spot can be disabled or configured as a time window using the Maintenance Window option.

Revert to RI/SP​

The Elastigroup replacement process checks if there are any vacant reservations or savings plan every hour. It replaces any Spot instances with the applicable RI/SP instance types provided and utilizes the RI or the Commitments flag that is enabled for the group.

Revert to Preferred Spot​

If Elastigroup has preferred Spot instance types and the group runs more applicable instances in non-preferred markets due to market stability or pricing issues, then as soon as the preferred markets become available the replacement process will replace the non-preferred instances with the preferred Spot instance types.

Spot Market Scoring​

Spot markets are defined as the supply and demand for a specific instance type, at a specific spot price in a specific availability zone, for a specific product (for example, Linux or Windows). Spot markets are ranked by Elastigroup based on real-time and historical data on availability and cost, enabling Elastigroup to predict interruptions to instances in a market up to an hour in advance during peak business hours. This advance notification on upcoming interruptions is what triggers the spot instance replacement and ensures the continuous availability of your workloads.