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fix(autoscaling): every deployment resets capacity
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If `DesiredCapacity` is specified in the CloudFormation template, on every
deployment the capacity of the AutoScalingGroup is reset to that number,
even if the group had been scaled out at that point. The solution is to
leave DesiredCapacity empty, in which case it will remain untouched
during a deployment.

Previously, CDK would use some logic to always calculate a
DesiredCapacity for you, even if you left the `desiredCapacity` property
unset, leading to the undesirable behavior--which frankly represents
an availability risk.

Now, if you don't specify `desiredCapacity`, we won't set
`DesiredCapacity` either, avoiding the availability risk that we
introduced beforehand. In fact, if you *do* set `desiredCapacity`, we
will warn you that you probably shouldn't using a construct warning.

Fixes #5215, closes #5208.

BREAKING CHANGE: AutoScalingGroups without `desiredCapacity` are now
initially scaled to their minimum capacity (instead of their maximum
capaciety).
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@rix0rrr
rix0rrr committed Dec 20, 2019
1 parent 5a4874b commit da4ac95
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Showing 24 changed files with 157 additions and 247 deletions.
27 changes: 20 additions & 7 deletions packages/@aws-cdk/aws-autoscaling/lib/auto-scaling-group.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,10 @@ export interface CommonAutoScalingGroupProps {
/**
* Initial amount of instances in the fleet
*
* @default 1
* If this is set to a number, every deployment will reset the amount of
* instances to this number. It is recommended to leave this value blank.
*
* @default minCapacity, and leave unchanged during deployment
*/
readonly desiredCapacity?: number;

Expand Down Expand Up @@ -475,30 +478,40 @@ export class AutoScalingGroup extends AutoScalingGroupBase implements

launchConfig.node.addDependency(this.role);

const desiredCapacity =
(props.desiredCapacity !== undefined ? props.desiredCapacity :
(props.minCapacity !== undefined ? props.minCapacity :
(props.maxCapacity !== undefined ? props.maxCapacity : 1)));
// desiredCapacity just reflects what the user has supplied.
const desiredCapacity = props.desiredCapacity;
const minCapacity = props.minCapacity !== undefined ? props.minCapacity : 1;
const maxCapacity = props.maxCapacity !== undefined ? props.maxCapacity : desiredCapacity;
const maxCapacity = props.maxCapacity !== undefined ? props.maxCapacity :
desiredCapacity !== undefined ? desiredCapacity : Math.max(minCapacity, 1);

withResolved(minCapacity, maxCapacity, (min, max) => {
if (min > max) {
throw new Error(`minCapacity (${min}) should be <= maxCapacity (${max})`);
}
});
withResolved(desiredCapacity, minCapacity, (desired, min) => {
if (desired === undefined) { return; }
if (desired < min) {
throw new Error(`Should have minCapacity (${min}) <= desiredCapacity (${desired})`);
}
});
withResolved(desiredCapacity, maxCapacity, (desired, max) => {
if (desired === undefined) { return; }
if (max < desired) {
throw new Error(`Should have desiredCapacity (${desired}) <= maxCapacity (${max})`);
}
});

if (desiredCapacity !== undefined) {
this.node.addWarning(`desiredCapacity has been configured. Be aware this will reset the size of your AutoScalingGroup on every deployment.`);
}

const { subnetIds, hasPublic } = props.vpc.selectSubnets(props.vpcSubnets);
const asgProps: CfnAutoScalingGroupProps = {
cooldown: props.cooldown !== undefined ? props.cooldown.toSeconds().toString() : undefined,
minSize: Tokenization.stringifyNumber(minCapacity),
maxSize: Tokenization.stringifyNumber(maxCapacity),
desiredCapacity: Tokenization.stringifyNumber(desiredCapacity),
desiredCapacity: desiredCapacity !== undefined ? Tokenization.stringifyNumber(desiredCapacity) : undefined,
launchConfigurationName: launchConfig.ref,
loadBalancerNames: Lazy.listValue({ produce: () => this.loadBalancerNames }, { omitEmpty: true }),
targetGroupArns: Lazy.listValue({ produce: () => this.targetGroupArns }, { omitEmpty: true }),
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1 change: 0 additions & 1 deletion packages/@aws-cdk/aws-autoscaling/test/integ.amazonlinux2.expected.json
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Expand Up @@ -451,7 +451,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "FleetLaunchConfig59F79D36"
},
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1 change: 0 additions & 1 deletion packages/@aws-cdk/aws-autoscaling/test/integ.asg-w-classic-loadbalancer.expected.json
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Expand Up @@ -631,7 +631,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "FleetLaunchConfig59F79D36"
},
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1 change: 0 additions & 1 deletion packages/@aws-cdk/aws-autoscaling/test/integ.asg-w-elbv2.expected.json
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Expand Up @@ -472,7 +472,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "FleetLaunchConfig59F79D36"
},
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1 change: 0 additions & 1 deletion packages/@aws-cdk/aws-autoscaling/test/integ.custom-scaling.expected.json
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Expand Up @@ -451,7 +451,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "FleetLaunchConfig59F79D36"
},
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1 change: 0 additions & 1 deletion packages/@aws-cdk/aws-autoscaling/test/integ.external-role.expected.json
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Expand Up @@ -604,7 +604,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "ASGLaunchConfigC00AF12B"
},
Expand Down
1 change: 0 additions & 1 deletion packages/@aws-cdk/aws-autoscaling/test/integ.spot-instances.expected.json
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Original file line number Diff line number Diff line change
Expand Up @@ -452,7 +452,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "FleetLaunchConfig59F79D36"
},
Expand Down
5 changes: 1 addition & 4 deletions packages/@aws-cdk/aws-autoscaling/test/test.auto-scaling-group.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -113,7 +113,6 @@ export = {
}
},
"Properties": {
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "MyFleetLaunchConfig5D7F9801"
},
Expand Down Expand Up @@ -252,7 +251,6 @@ export = {
expect(stack).to(haveResource("AWS::AutoScaling::AutoScalingGroup", {
MinSize: "10",
MaxSize: "10",
DesiredCapacity: "10",
}
));

Expand All @@ -275,8 +273,7 @@ export = {
// THEN
expect(stack).to(haveResource("AWS::AutoScaling::AutoScalingGroup", {
MinSize: "1",
MaxSize: "10",
DesiredCapacity: "10",
MaxSize: "10"
}
));

Expand Down
1 change: 0 additions & 1 deletion packages/@aws-cdk/aws-autoscaling/test/test.scheduled-action.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,6 @@ export = {
Properties: {
MaxSize: "1",
MinSize: "1",
DesiredCapacity: "1",
LaunchConfigurationName: { Ref: "ASGLaunchConfigC00AF12B" },
Tags: [
{
Expand Down
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-codedeploy/test/server/integ.deployment-group.expected.json
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Expand Up @@ -683,7 +683,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "ASGLaunchConfigC00AF12B"
},
Expand Down Expand Up @@ -885,4 +884,4 @@
"Default": "/aws/service/ami-amazon-linux-latest/amzn-ami-hvm-x86_64-gp2"
}
}
}
}
3 changes: 1 addition & 2 deletions ...-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service.expected.json
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Expand Up @@ -519,7 +519,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "ClusterDefaultAutoScalingGroupLaunchConfig81EA5466"
},
Expand Down Expand Up @@ -1152,4 +1151,4 @@
}
}
}
}
}
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-ecs-patterns/test/ec2/integ.scheduled-ecs-task.lit.expected.json
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Expand Up @@ -339,7 +339,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -856,4 +855,4 @@
"Default": "/aws/service/ecs/optimized-ami/amazon-linux-2/recommended/image_id"
}
}
}
}
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-ecs/test/ec2/integ.app-mesh-proxy-config.expected.json
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Expand Up @@ -498,7 +498,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -939,4 +938,4 @@
"Default": "/aws/service/ecs/optimized-ami/amazon-linux-2/recommended/image_id"
}
}
}
}
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-ecs/test/ec2/integ.clb-host-nw.expected.json
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Expand Up @@ -519,7 +519,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -987,4 +986,4 @@
}
}
}
}
}
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-ecs/test/ec2/integ.lb-awsvpc-nw.expected.json
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Expand Up @@ -498,7 +498,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -1053,4 +1052,4 @@
}
}
}
}
}
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-ecs/test/ec2/integ.lb-bridge-nw.expected.json
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Expand Up @@ -519,7 +519,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -1017,4 +1016,4 @@
}
}
}
}
}
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-ecs/test/ec2/integ.sd-awsvpc-nw.expected.json
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Expand Up @@ -498,7 +498,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -963,4 +962,4 @@
"Default": "/aws/service/ecs/optimized-ami/amazon-linux-2/recommended/image_id"
}
}
}
}
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-ecs/test/ec2/integ.sd-bridge-nw.expected.json
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Original file line number Diff line number Diff line change
Expand Up @@ -498,7 +498,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -928,4 +927,4 @@
"Default": "/aws/service/ecs/optimized-ami/amazon-linux-2/recommended/image_id"
}
}
}
}
2 changes: 1 addition & 1 deletion packages/@aws-cdk/aws-ecs/test/ec2/integ.spot-drain.expected.json
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Expand Up @@ -1323,4 +1323,4 @@
"Default": "/aws/service/ecs/optimized-ami/amazon-linux-2/recommended/image_id"
}
}
}
}
4 changes: 0 additions & 4 deletions packages/@aws-cdk/aws-ecs/test/test.ecs-cluster.ts
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Expand Up @@ -67,7 +67,6 @@ export = {
expect(stack).to(haveResource("AWS::AutoScaling::AutoScalingGroup", {
MaxSize: "1",
MinSize: "1",
DesiredCapacity: "1",
LaunchConfigurationName: {
Ref: "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -213,7 +212,6 @@ export = {
expect(stack).to(haveResource("AWS::AutoScaling::AutoScalingGroup", {
MaxSize: "1",
MinSize: "1",
DesiredCapacity: "1",
LaunchConfigurationName: {
Ref: "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -514,7 +512,6 @@ export = {
expect(stack).to(haveResource("AWS::AutoScaling::AutoScalingGroup", {
MaxSize: "1",
MinSize: "1",
DesiredCapacity: "1",
LaunchConfigurationName: {
Ref: "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -1273,7 +1270,6 @@ export = {
expect(stack).to(haveResource("AWS::AutoScaling::AutoScalingGroup", {
MaxSize: "1",
MinSize: "1",
DesiredCapacity: "1",
LaunchConfigurationName: {
Ref: "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-eks/test/integ.eks-spot.expected.json
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Expand Up @@ -1310,7 +1310,6 @@
"Properties": {
"MaxSize": "10",
"MinSize": "1",
"DesiredCapacity": "10",
"LaunchConfigurationName": {
"Ref": "myClusterspotLaunchConfig6681F311"
},
Expand Down Expand Up @@ -1449,4 +1448,4 @@
"Default": "/aws/service/eks/optimized-ami/1.14/amazon-linux-2/recommended/image_id"
}
}
}
}
3 changes: 1 addition & 2 deletions packages/@aws-cdk/aws-events-targets/test/ecs/integ.event-ec2-task.lit.expected.json
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Expand Up @@ -339,7 +339,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "EcsClusterDefaultAutoScalingGroupLaunchConfigB7E376C1"
},
Expand Down Expand Up @@ -1125,4 +1124,4 @@
"Description": "Artifact hash for asset \"ea7034d81c091be1158bcd85b4958dc86ec6672c345be27607d68fdfcf26b1c1\""
}
}
}
}
1 change: 0 additions & 1 deletion packages/@aws-cdk/aws-stepfunctions-tasks/test/integ.ec2-task.expected.json
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Expand Up @@ -141,7 +141,6 @@
"Properties": {
"MaxSize": "1",
"MinSize": "1",
"DesiredCapacity": "1",
"LaunchConfigurationName": {
"Ref": "FargateClusterDefaultAutoScalingGroupLaunchConfig57306899"
},
Expand Down
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