Pull Information Using a Block of Data from an Existing Resource “aws_cloudwatch_event_rule”

We can retrieve information using a data block from an existing aws_cloudwatch_event_rule resource in Terraform. Terraform’s data block provides a way to query and read details about existing resources in your AWS environment without managing their lifecycle.

1. Understanding the Data Block

The data block allows you to fetch and use information about existing infrastructure components. We can utilize this feature to access details such as the ARN, schedule expression, event pattern, and more.

2. Defining Data Block

data "aws_cloudwatch_event_rule" "example" {
  name = "your-existing-rule-name"
}

Here, the name is the existing CloudWatch Event Rule you wish to query.

Attributes Available for use

1. arn
2. description
3. event_pattern
4. is_enabled
5. role_arn
6. schedule_expression

Example:

output "rule_arn" {
  value = data.aws_cloudwatch_event_rule.example.arn
}
output "is_enabled" {
 	 value = data.aws_cloudwatch_event_rule.example.is_enabled
}

Practical Use Case:

1. Integration with Dependent Resources: Referencing the Event Rule to create or configure dependent resources like event targets.
2. Verification: Validating the configuration of an existing rule through Terraform outputs.
3. Accessing Event Patterns: Using the event_pattern attribute for event-driven architecture workflows.

Example: Associating an Existing Rule with a Target

resource "aws_cloudwatch_event_target" "example" {
  rule = data.aws_cloudwatch_event_rule.example.name
  arn  = aws_lambda_function.example.arn
}