(aws-lambda): Alias.scaleOnSchedule() doesn't make clear which Schedule to use

[garysassano]

Describe the bug

Ambiguous Schedule import causing inconsistent behavior

There seems to be an issue with the Schedule import used in scaleOnSchedule. Depending on which AWS CDK library the Schedule class is imported from, the code exhibits different behavior:

• import { Schedule } from "aws-cdk-lib/aws-applicationautoscaling": Works
• import { Schedule } from "aws-cdk-lib/aws-events": Works
• import { Schedule } from "aws-cdk-lib/aws-autoscaling": Fails

Expected Behavior

The Schedule import should be unambiguous, and the code should function consistently regardless of which AWS CDK library it is imported from.

Current Behavior

You may import the wrong Schedule without noticing until deployment.

Reproduction Steps

Use the following code snippet:

const scalableFunction = new NodejsFunction(this, "ScalableFunction", {
  functionName: "scalable-function",
  entry: join(__dirname, "..", "functions", "scalable", "index.ts"),
  runtime: Runtime.NODEJS_20_X,
  architecture: Architecture.ARM_64,
  memorySize: 1024,
  timeout: Duration.minutes(5),
  loggingFormat: LoggingFormat.JSON,
});

const scalableFunctionAlias = new Alias(this, "ScalableFunctionAlias", {
  aliasName: "live",
  version: scalableFunction.currentVersion,
});

scalableFunctionAlias
  .addAutoScaling({
    minCapacity: 1,
    maxCapacity: 10,
  })
  .scaleOnSchedule("ScaleUpInMorning", {
    schedule: Schedule.cron({ hour: "3", minute: "30" }), // Change the import to test different scenarios
    minCapacity: 5,
  });

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.145.0

Framework Version

No response

Node.js Version

20.13.1

OS

Ubuntu 22.04.3 LTS

Language

TypeScript

Language Version

No response

Other information

No response

[garysassano]

Weirdly enough, it looks like the only module that didn't work for me is present as a docs example HERE.

[khushail]

Hi @garysassano , thanks for reporting this. I agree that it should behave same irrespective of which import is used.

However upon verification, I noticed that the generated cron() schedule should be synthesized to this
which deploys successfully -

"Schedule": "cron(30 3 * * ? *)",

which is uniformly implemented in aws-events and aws-applicationautoscaling as seen here -

aws-cdk/packages/aws-cdk-lib/aws-events/lib/schedule.ts

Line 62 in 7f5ce4b

public readonly expressionString: string = `cron(${minute} ${hour} ${day} ${month} ${weekDay} ${year})`;

aws-cdk/packages/aws-cdk-lib/aws-applicationautoscaling/lib/schedule.ts

Line 63 in 7f5ce4b

public readonly expressionString: string = `cron(${minute} ${hour} ${day} ${month} ${weekDay} ${year})`;

but the return expression in case of aws-autoscaling is different -

aws-cdk/packages/aws-cdk-lib/aws-autoscaling/lib/schedule.ts

Line 33 in 7f5ce4b

public readonly expressionString: string = `${minute} ${hour} ${day} ${month} ${weekDay}`;

which generates this expression in Synthesized template

"Schedule": "30 3 * * *"

which fails eventually during deployment.