Rails 6.1 allows per environment configuration support for Active Storage

Rails 6.1 allows environment-specific configuration files to set up Active Storage.

In development, the config/storage/development.yml file will take precedence over the config/storage.yml file. Similarly, in production, the config/storage/production.yml file will take precedence.

If an environment-specific configuration is not present, Rails will fall back to the configuration declared in config/storage.yml.

Why was it needed?

Before Rails 6.1, all storage services were defined in one file, each environment could set its preferred service in config.active_storage.service, and that service would be used for all attachments.

Now we can override the default application-wide storage service for any attachment, like this:

1class User < ApplicationModel
2  has_one_attached :avatar, service: :amazon_s3
3end
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And we can declare a custom amazon_s3 service in the config/storage.yml file:

1amazon_s3:
2  service: S3
3  bucket: "..."
4  access_key_id: "..."
5  secret_access_key: "..."
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But we are still using the same service for storing avatars in both production and development environments.

To use a separate service per environment, Rails allows the creation of configuration files for each.

How do we do that?

Let's change the service to something more generic in the User model:

1class User < ApplicationModel
2  has_one_attached :avatar, service: :store_avatars
3end
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And add some environment configurations:

For production we'll add config/storage/production.yml:

1store_avatars:
2  service: S3
3  bucket: "..."
4  access_key_id: "..."
5  secret_access_key: "..."
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And for development we'll add config/storage/development.yml:

1store_avatars:
2  service: Disk
3  root: <%= Rails.root.join("storage") %>
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This will ensure that Rails will store the avatars differently per environment.

Check out the pull request to learn more.