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How to ignore changes in Terraform

Jul 23, 2021 · 1 min read · Post a comment
How to ignore changes in Terraform

Terraform is the most popular Infrastructure as Code tool mostly used for spinning up and managing infrastructure on the public cloud giants AWS, Azure, GCP and DigitalOcean. But, sometimes it doesn’t work the way we plan, and resources could be lost if not being careful. And, if you have worked before with Terraform, you’ve most likely dealt with that one annoying resource attribute that doesn’t change but it props at every terraform apply. The reasons could be intended or unintender (bugs). Let’s see an example of how can we get rid of that annoying resource attribute.

Prerequisites

  • Terraform

Example

Let’s say we have an AWS elasticsearch module. If we don’t want to add some logs initially to the cluster, we need to update the log_publishing_options attribute to disabled.

resource "aws_elasticsearch_domain" "this" {
. . . 
    log_publishing_options {
        enabled                  = false
        log_type                 = var.cloudwatch_log_type
        cloudwatch_log_group_arn = var.cloudwatch_log_group_arn
    }
}

Now, if we run terraform plan and/or terraform apply, we’ll get the following output every time:

- log_publishing_options {
          - enabled  = false -> null
          - log_type = "INDEX_SLOW_LOGS" -> null
        }

The solution

The lifecycle block comes to the rescue:

resource "aws_elasticsearch_domain" "this" {
. . . 
    lifecycle {
        ignore_changes = [log_publishing_options]
    }
}

Now, thanks to the ignore_changes feature, we can basically ignore any resource attribute that cause us trouble.

Conclusion

There is an open issue regarding the log_publishing_option which can be found on Github.
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