How to Avoid Terraform Apply from Forcefully Recreating Google Cloud Storage Object

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Introduction

This article provides instructions for how to avoid the following terraform apply runs to recreate the already-existing Google Cloud Storage (GCS) objects that were created in the previous apply run.

Problem

Users have updated their terraform codes and left the part of codes containing GCS object resources unchanged. When executing a plan run, the plan outputs report that the GCS objects are subject to be recreated. Users may also see the same even when no changes have been made to the codes and submit another planor apply run. The plan outputs always tell that the GCS objects will be recreated because a different hash is detected.

Solution

The way to prevent Terraform from recreating the GCS object is by adding detect_md5hash in the resource block. Here are the steps to generate the md5hash for a GCS object and add it to the resource.

• Run gsutil to calculate the md5hash value,

  gsutil hash -m sample_file.txt

  The command output will look like this,

  Hashes [base64] for sample_file.txt:
         Hash (md5): UXeljcZcihTckMads7890g==
  
  Operation completed over 1 objects/7.0 B.

• Copy the calculated hash value and add it to the resource block,

  resource "google_storage_bucket_object" "default" {
    name = "sample_file.txt"
    source = "./sample_file.txt"
    detect_md5hash = "UXeljcZcihTckMads7890g=="
    bucket = google_storage_bucket.static.id
  }

Outcome

On the first apply run, the GCS object will be created. The GCS object will not be recreated after submitting another apply run. 

Additional Information

• Calculate file hashes using gsutil hash