Fix Terraform EventBridge Rule - ResourceAlreadyExistsException

Quick Answer

An EventBridge rule with the same name already exists on the event bus. Import it into Terraform, use environment-prefixed names, or delete the orphaned rule.

The Error

Error: creating EventBridge Rule (my-schedule-rule):
  ResourceAlreadyExistsException: Rule my-schedule-rule already exists on EventBus default.

What Causes This Error

1. Rule created manually via Console, CLI, or another IaC tool
2. Another Terraform workspace manages the same rule name
3. Failed previous apply — rule was created but not recorded in state
4. Same rule name on different event bus — rule names are unique per event bus

How to Fix It

Solution 1: Import the Existing Rule

# Check if the rule exists
aws events describe-rule --name my-schedule-rule
 
# Import — format: event_bus_name/rule_name
terraform import aws_cloudwatch_event_rule.schedule default/my-schedule-rule
 
# For custom event bus
terraform import aws_cloudwatch_event_rule.schedule my-bus/my-schedule-rule

Solution 2: Use Unique Names

resource "aws_cloudwatch_event_rule" "schedule" {
  name                = "${var.project}-${var.environment}-daily-cleanup"
  description         = "Trigger daily cleanup Lambda"
  schedule_expression = "cron(0 2 * * ? *)"
  event_bus_name      = "default"
}
 
resource "aws_cloudwatch_event_target" "lambda" {
  rule = aws_cloudwatch_event_rule.schedule.name
  arn  = aws_lambda_function.cleanup.arn
}

Solution 3: Use Custom Event Bus

Isolate rules per application with custom event buses:

resource "aws_cloudwatch_event_bus" "app" {
  name = "${var.project}-${var.environment}"
}
 
resource "aws_cloudwatch_event_rule" "process_orders" {
  name           = "process-orders"
  event_bus_name = aws_cloudwatch_event_bus.app.name
 
  event_pattern = jsonencode({
    source      = ["com.myapp.orders"]
    detail-type = ["OrderCreated"]
  })
}

Troubleshooting Checklist

1. ✅ Does the rule exist? (aws events describe-rule --name NAME)
2. ✅ Which event bus is it on? (default or custom)
3. ✅ Should you import or delete it?
4. ✅ Are you using unique names per environment?

Prevention Tips

• Prefix rule names with project and environment
• Use custom event buses to isolate applications
• Tag rules with ManagedBy = "terraform"
• Import existing rules before trying to recreate

Related Articles

• All Troubleshooting Articles
• Terraform Glossary

Conclusion

EventBridge rule names must be unique per event bus. Import existing rules, use environment-prefixed names, or isolate applications with custom event buses to prevent naming conflicts.