Scale down dynamo

[FractalJim]

Dynamo tables can also consume a lot of resource when not in use. Though you can use auto-scaling, you wont necessarily be scaling down to 1. So if hammertime reduced read and write capacity of tables to 1 outside business hours and set back to what it was (including autoscaling settings) when it restored this could save some money.

[ramesius]

Hi, thanks for the suggestion. Should be easy to implement, using these APIs:

• https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#tagResource-property
• https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#updateTable-property
• https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#listTables-property
• https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#listGlobalTables-property

We would need to identify any indexes on a table and scale those down too.

Dealing with tables that have autoscaling enabled might a bit tricky, we would have to query other AWS resources to find those I think, this also goes for indexes that might have auto-scaling.

[ramesius]

For auto-scaled tables, we would need to query this API:

• https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/ApplicationAutoScaling.html

Using a ServiceNamespace of 'dynamodb' should do the trick, but it looks like these resources do not support tagging for us to record previous values prior the hammertime run.

[FractalJim]

Could you not tag the tables themselves?

[ramesius]

Yeah we could definetly do that, good idea. 👍

[ramesius]

For tables without autoscaling it should be fairly simple to record previous values:

• hammertime:readunits
• hammertime:writeunits
  This would be the same for indexes that have no autoscaling.

For autoscaling I think we would need to store upto 6 values:

• hammertime:autoscale-minreadunits
• hammertime:autoscale-maxreadunits
• hammertime:autoscale-minwriteunits
• hammertime:autoscale-maxwriteunits
• hammertime:autoscale-readutilization
• hammertime:autoscale-writeutilization

Looks like we would also have to query this API to get the scalable targets https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/ApplicationAutoScaling.html#describeScalableTargets-property as well as this to update the Min and Max values https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/ApplicationAutoScaling.html#registerScalableTarget-property

[ramesius]

On second thought we might not have to store the read/write utilization values if we do not change them 🤔