Phantom Compute service changes caused by `source_code_hash` discrepancies
## Overview
Last week I noticed that the provider keeps reporting a pending change even though the Compute binary remains unchanged. No matter how many times you apply the change, the result is always identical:
```console
Terraform used the selected providers to generate the following execution
plan. Resource actions are indicated with the following symbols:
~ update in-place
Terraform will perform the following actions:
# module.compute.fastly_service_compute.foo will be updated in-place
~ resource "fastly_service_compute" "foo" {
~ active_version = 112 -> (known after apply)
~ cloned_version = 112 -> (known after apply)
~ package {
~ source_code_hash = "1c333507c41b9368bab1f27660af93adb0b08f916dc68abe06c08d0db1e114227fdc8556d0dae083fb833eb3a48a02ddfe5c3fee277cbc063661306d8842b708" -> "1f29ce557e72df67d5ad8afdf1843aab554fc9ab3a7296c94648d0307551265153df0880e03925a14563d7659135c5bf7489efb8a46cdbc18e6937e18ff5dfdb"
# (2 unchanged attributes hidden)
}
# (3 unchanged blocks hidden)
}
```
The API service receives only the binary (see [here](https://www.fastly.com/documentation/reference/api/services/package/#put-package)) and calculates both `files_hash` and `hashsum` (SHA512 of the binary) internally. However, the `files_hash` calculation (used for `source_code_hash` comparison later) apparently differs from the Terraform provider's calculation method:
https://github.com/fastly/terraform-provider-fastly/blob/6ede21c148d18089e04b3056160bae1ee2068786/fastly/data_source_package_hash.go#L151-L164
## Example
1. Starting point: the most recent version of my Compute service is 109
2. The binary I'm about to deploy looks as follows:
```console
$ sha512sum ../compute/src/pkg/foo.tar.gz
4a56a0b5deec7c3002606e3366f2b9215aff59443b8a406b388733eb61c5745098261b233a89bb42cdd2b0a605a545d1657174b5ba4046818729490ca2b58f46 ../compute/src/pkg/foo.tar.gz
```
3. I deployed the service using v8.5.0 of the provider, which created version 110 (irrelevant attributes removed):
```json
{
"created_at": "2025-12-01T12:26:47Z",
"id": "9elkprpciT1ZxuvOaNC9f0",
"metadata": {
"cloned_from": "https://github.com/fastly/compute-starter-kit-go-default",
"files_hash": "1c333507c41b9368bab1f27660af93adb0b08f916dc68abe06c08d0db1e114227fdc8556d0dae083fb833eb3a48a02ddfe5c3fee277cbc063661306d8842b708",
"hashsum": "4a56a0b5deec7c3002606e3366f2b9215aff59443b8a406b388733eb61c5745098261b233a89bb42cdd2b0a605a545d1657174b5ba4046818729490ca2b58f46",
"language": "go",
"name": "foo",
"size": 1823178
},
"updated_at": "2025-12-01T12:26:48Z",
"version": 110
}
```
4. I then used Terraform to deploy the identical binary again (the same phantom change appeared)
5. Terraform created and activated version 111
```json
{
"created_at": "2025-12-01T12:34:57Z",
"id": "qYUk3Y5fG5J2eVWSx0L0R2",
"metadata": {
"cloned_from": "https://github.com/fastly/compute-starter-kit-go-default",
"files_hash": "1c333507c41b9368bab1f27660af93adb0b08f916dc68abe06c08d0db1e114227fdc8556d0dae083fb833eb3a48a02ddfe5c3fee277cbc063661306d8842b708",
"hashsum": "4a56a0b5deec7c3002606e3366f2b9215aff59443b8a406b388733eb61c5745098261b233a89bb42cdd2b0a605a545d1657174b5ba4046818729490ca2b58f46",
"language": "go",
"name": "foo",
"size": 1823178
},
"updated_at": "2025-12-01T12:34:57Z",
"version": 111
}
```
8 条评论