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Align EventBridge schedules with Pacific Time #1

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69a2441
Align schedules with Pacific Time timezone support
darindeters Oct 15, 2025
f58fd6b
Clarify schedule documentation
darindeters Oct 15, 2025
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5 changes: 3 additions & 2 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ This AWS CloudFormation stack resizes EC2 instances on a schedule to optimize co
## 🔧 How It Works

- A Lambda function runs twice per day via EventBridge rules:
- **7 PM Pacific** — Scales down tagged instances to a smaller type (e.g. `t3.medium`)
- **7 PM Pacific (Mon–Fri only)** — Scales down tagged instances to a smaller type (e.g. `t3.medium`)
- **4 AM Pacific (Mon–Fri only)** — Scales them back up to the original size
- Instances are rebooted once per resize operation (stop → modify → start)
- This works even if you're using Compute Savings Plans
Expand Down Expand Up @@ -44,7 +44,8 @@ To deploy with AWS Console:
## 📝 Customization

- **Resize Target:** The off-hours instance type defaults to `t3.medium`. You can change this in the Lambda code.
- **Schedule:** Default schedule is hardcoded for Pacific Time. You can update the EventBridge cron rules if needed.
- **Schedule:** Default EventBridge cron rules are pinned to 4 AM and 7 PM Pacific (with automatic DST handling via `ScheduleExpressionTimezone: America/Los_Angeles`). Update the `LambdaScheduleUpTime`/`LambdaScheduleDownTime` parameters if you need different windows.
- **Redeployment:** Deploy or update the CloudFormation stack after changing schedule parameters so the EventBridge rules pick up the new cron expressions and timezone.
- **Logging:** CloudWatch Log Group is created with 14-day retention. Logs show success and error messages per instance.

## 🧪 Testing
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6 changes: 4 additions & 2 deletions ec2-dynamic-scheduler.yaml
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Expand Up @@ -7,10 +7,10 @@ Parameters:
Default: DynamicEC2Scheduler
LambdaScheduleUpTime:
Type: String
Default: "cron(0 11 ? * MON-FRI *)"
Default: "cron(0 4 ? * MON-FRI *)"
LambdaScheduleDownTime:
Type: String
Default: "cron(0 2 ? * MON-FRI *)"
Default: "cron(0 19 ? * MON-FRI *)"

Resources:

Expand Down Expand Up @@ -172,6 +172,7 @@ Resources:
Name: EC2ScalerScheduleDown
Description: Triggers Lambda to scale down EC2 instances at 7 PM Pacific, Monday through Friday
ScheduleExpression: !Ref LambdaScheduleDownTime
ScheduleExpressionTimezone: America/Los_Angeles
State: ENABLED
Targets:
- Arn: !GetAtt EC2ScalerFunction.Arn
Expand All @@ -185,6 +186,7 @@ Resources:
Name: EC2ScalerScheduleUp
Description: Triggers Lambda to scale up EC2 instances at 4 AM Pacific, Monday through Friday
ScheduleExpression: !Ref LambdaScheduleUpTime
ScheduleExpressionTimezone: America/Los_Angeles
State: ENABLED
Targets:
- Arn: !GetAtt EC2ScalerFunction.Arn
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