Lambda datasource that returns multiple functions and allows filters

[srkiNZ84]

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Description

At the moment, for AWS Lambda, there only appears to be a "aws_lambda_function" datasource that returns a single function and that you have to know the name of the function for:

https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/lambda_function

This issue is a proposal is for a new "aws_lambda_functions" datasource that returns zero or more lambda functions based on a filter, like the "aws_instances" datasource (https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/instances) but for Lambda functions.

Why?

I would like to use this datasource to feed it into a CloudWatch alarms resources and create an "alarm per function" to make it simpler to diagnose issues (in the current state, we have alarms which trigger if any lambda throws an error, which leaves the task of figuring out which Lambda it was to the unfortunate operator).

There are possible other use cases, basically any situation where you need a list of Lambda functions to create a "per function" resource as an example

New or Affected Resource(s)

• aws_lambda_functions (new datasource)

Potential Terraform Configuration

data "aws_lambda_functions" "test" {
  lambda_tags = {
    Environment = "Test"
  }

  filter {
    name   = "lambda.runtime"
    values = ["Python 3.7"]
  }
}

resource "aws_cloudwatch_metric_alarm" "lambda_error_alarm" {
  count                     = length(data.aws_lambda_functions.test.ids)
  alarm_name                = "${data.aws_lambda_functions.test.name[count.index]}-lambda-error"
  comparison_operator       = "GreaterThanOrEqualToThreshold"
  evaluation_periods        = "2"
  threshold                 = "5"
  period                    = "60"
  alarm_description         = "Alarm triggers when the number of Lambda invocation errors goes above 5 in a one minute period for two consecutive minutes"
  alarm_actions             = [aws_sns_topic.system_alarms.arn]
  metric_name               = "Errors"
  namespace                 = "AWS/Lambda"
  dimensions = {
        FunctionName = data.aws_lambda_functions.test.name[count.index]
  }
  statistic                 = "Sum"
  insufficient_data_actions = []
}

References

N/A

[DrFaust92]

While there is a "ListFunctions" operations thats supported by the SDK, there isnt a way to filter by tags.
Adding the custom logic to filter after fetching is usually a maintenance burden as the api may expose this functionality later and break the provider's behaviour.

i believe maintainers wouldn't be for adding this custom logic if a data source for multiple lambda functions is added but ill leave the final say to them. just giving my two cents here.

A possible better solution that doesnt require custom logic is to implement the tagging group data source (corresponding to this https://docs.aws.amazon.com/resourcegroupstagging/latest/APIReference/API_GetResources.html) that allows a generic solution for fetching resource by tag instead of service specific datasource.

[github-actions]

This functionality has been released in v4.47.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
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