Set the minInstancesInServiceParameters property
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This is to allow testing of guardian/riff-raff#1383 whilst the `riff-raff.yaml` generator from GuCDK hasn't been updated.
akash1810
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minInstancesInServiceParameters property
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What does this change?
This is to allow testing of guardian/riff-raff#1383 whilst the
riff-raff.yamlgenerator from GuCDK hasn't been updated.This
riff-raff.yamlis a stripped down version of the generated one, only uploading the application artifact to S3, and deploying the application CloudFormation stack.How to test?
This branch can test multiple scenarios.
Note
All scenarios match previously observed behaviour regarding number of in service instances.
"Normal" capacity (i.e.
desired = min)With the ASG operating at normal capacity, the deployment was also normal.
The deployment log also shows the value of the
MinInstancesInServiceForcdkplaygroundCFN parameter was, expectedly, set to match the desired capacity (1).Partially scaled (i.e.
min < desired < max)Before a deployment was started, the
scale-outscript was executed a few times, causing the ASG to havemin=1,desired=5,max=10.The deployment was normal and the deployment log shows the value of the
MinInstancesInServiceForcdkplaygroundCFN parameter was, expectedly, set to match the current desired capacity (5):The metrics show the ALB's healthy host count never dropped below 5. That is, there was no degradation in service availability.
Fully scaled (i.e.
desired = max)Before a deployment was started, the
scale-outscript was executed a few times, causing the ASG to havemin=1,desired=10,max=10.The deployment was predictably slow as it operated as a "one out, one in" update. The deployment log shows the value of the
MinInstancesInServiceForcdkplaygroundCFN parameter was, expectedly, set to 7 (75% of max, rounded down):The metrics show the ALB's healthy host count dropped to 7, as expected. Whilst this results in a drop in availability, it is an unusual scenario as scaling to max is indicative of incorrect capacity planning. That is, the max should be higher.