Remote DiskService through SFTP, for ActiveStorage.

Add this line to your application's Gemfile:

gem 'activestorage-sftp'

And then execute:

$ bundle

Or install it yourself as:

$ gem install activestorage-sftp

Each application server saves blobs to file server through SFTP:

# config/storage.yml
sftp:
  service: SFTP
  user: user
  root: /var/www/proj/shared/storage
  host: file.intranet
  public_host: https://file.internet
  password: <%= ENV['PASSWORD'] %> # optional

File server serves blobs using DiskService:

# config/storage.yml
local:
  service: Disk
  root: <%= Rails.root.join("storage") %>

Or use it as backup for your primary service:

# config/storage.yml
mirrored:
  service: Mirror
  primary: local #/S3/AzureStorage/GCS
  mirrors:
    - sftp
sftp:
  service: SFTP
  user: user
  root: /etc/backup/proj
  host: secure.backup

By default the generated URLs will include parameters for content_disposition, expiration hints etc. A generated blobs URL might thus look like:

https://publichost/PATH/rails/active_storage/disk/hash-hash/name.JPG?content_type=image%2Fjpeg&disposition=inline%3B+filename%3D

If you prefer simple URLs like

https://publichost/PATH/hash

you can set a configuration option:

# config/storage.yml
sftp:
  simple_public_urls: true # defaults to false

The default way of verifying that a blob does exist is to login to the sftp server and stat() the relevant file. This is done e.g. before re-transforming and uploading an image variant. While other "caching" solutions exist to speed up that process, a simple and efficient way of verifying the existence of a file is to query the relevant server with an HTTP HEAD request. Depending on the setup this might not always be a viable way, so it can be switched on with a configuration option.

# config/storage.yml
sftp:
  verify_via_http_get: true # defaults to false

Bug reports and pull requests are welcome on GitHub at https://github.com/treenewbee/activestorage-sftp.

The gem is available as open source under the terms of the MIT License.