Conditionally enabling an event schedule in AWS sam template file

Question

This is my (shortened) template.yml file:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: CF template for foobar

Parameters:
  EnvType:
    Type: String
    Description: The environment to deploy to.
    AllowedValues:
      - dev1
      - qc1
      - uat1
    Default: dev1

  VeryImportantFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: src/very_important/
      Handler: app.very_important
      Runtime: python3.8
      {unrelated policies and environment variables}
      Events:
        VeryImportantSchedule:
          Type: Schedule
          Properties:
            Schedule: 'rate(2 hours)'
            Enabled: True

What I am trying to do is only enable that schedule when the EnvType parameter is set to qc1. The problem is, I can't get either the Equals condition or the If condition to work. I have tried all of the following:

Enabled: !Equals [!Ref EnvType, qc1]
Enabled: !Equals [!Ref EnvType, "qc1"]

and

Conditions:
  IsQcEnv: !Equals [!Ref EnvType, qc1]
  {and}
  IsQcEnv: !Equals [!Ref EnvType, "qc1"]

....
....
....
      Events:
        VeryImportantSchedule:
          Type: Schedule
          Properties:
            Schedule: 'rate(2 hours)'
            Enabled: !If [IsQcEnv, True, False]

In between testing all four of those cases, I deleted my entire stack rather than trying to update them, as a comment in this post suggested. I also triple checked that the parameter being passed in is not qc1, and also just set the Enabled flag to False to make sure that it would actually disable the schedule, which it did. At this point I'm stumped, does anyone have any idea of what I'm doing wrong or what I could try?

Why it does not work? Any error messages? Parring erros? Syntax errors? Stack rollbacks? — Marcin
– Marcin, Commented Apr 15, 2021 at 23:57
@Marcin: I had the same problem. AWS does not complain, but the schedule is always enabled. — binford
– binford, Commented Jun 12, 2021 at 10:46

binford · Accepted Answer · 2021-06-12 10:45:05Z

5

I had the same problem. Apparently the Enabled property does not work well with !If or !Equals. I fixed it with a hack in the Schedule property:

 Events:
   InvocationLevel:
     Type: Schedule
     Properties:
        Schedule: !If [IsQcEnv, "rate(2 hours)", "cron(0 0 31 2 ? *)"]

If the envType is not qc1, the cron expression will be used. This expression will execute your function on February 31st. Which means it will never execute.

I found this solution with help from those answers:

https://stackoverflow.com/a/65214717/517173

https://stackoverflow.com/a/13938155/517173

answered Jun 12, 2021 at 10:45

binford

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1 Comment

ConorBaumgart Over a year ago

My team and I just got around to trying this and it works! Thanks so much :)

rbu · Accepted Answer · 2025-11-05 11:45:54Z

0

This looks like another instance of an infamous SAM bug where intrinsic functions do not work for some properties, but only in AWS:Serverless resources. A known workaround is to include the AWS::LanguageExtensions transform before Serverless like this:

Transform:
  - AWS::LanguageExtensions
  - AWS::Serverless-2016-10-31

answered Nov 5 at 11:45

rbu

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Comments

Алексей Ковальчук · Accepted Answer · 2025-11-21 10:20:36Z

0

There is option to use state: https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/sam-property-function-schedule.html#sam-function-schedule-state

It disables the rule.

answered yesterday

Алексей Ковальчук

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