Preemptible instances in E-MapReduce (EMR) are suitable for scenarios where there are no requirements on the execution of big data jobs, but the cost of computing resources is a major concern. With the auto scaling feature, you can purchase preemptible instances to increase the computing resources of clusters.

Enable auto scaling

To enable auto scaling and configure scaling rules, follow these steps:
  1. Log on to the Alibaba Cloud E-MapReduce console.
  2. Click the Cluster Management tab.
  3. Find the target cluster and click Details in the Actions column.
  4. In the left-side navigation pane of the Cluster Overview page that appears, click Auto Scaling.
  5. On the Auto Scaling page that appears, click Enable Auto Scaling in the upper-right corner.
  6. Configure scaling rules. For more information, see Configure auto scaling rules by time.
  7. In the Scaling Settings section, select Spot Instance for Billing Method.

Configure preemptible instances

Note A preemptible instance is more cost-effective than a pay-as-you-go instance, but Alibaba Cloud may release your preemptible instances at any time based on changes in the supply and demand of resources or market exchange values.
Scaling Settings section
To configure preemptible instances, follow these steps:
  1. Specify vCPU and Memory.
  2. Select instance types. EMR automatically selects all the instance types that meet specifications. You can select up to three instance types to ensure that you can purchase preemptible instances as often as you require.
  3. Specify Maximum Cost Per Instance Type for each instance type and click OK. The selected instance types appear in the Selected column. If you want to change the price of a selected instance type, select the instance type in the Available list and modify Maximum Cost Per Instance Type (which is calculated on an hourly basis). Your instance starts to run if your bid is higher than the current market price. The system charges you the market price for the final instance types you use.
  4. Adjust the data disk size based on your needs. The system disk is used to deploy the operating system and basic EMR services. You do not need to adjust the disk size.
  5. Click Save. The final configuration price is calculated as follows: Maximum instance bid + Price of the system disk + Total price of data disks.

For more information about preemptible instances, see Instance FAQ.