1 What is Active Storage?
Active Storage facilitates uploading files to a cloud storage service like Amazon S3, Google Cloud Storage, or Microsoft Azure Storage and attaching those files to Active Record objects. It comes with a local disk-based service for development and testing and supports mirroring files to subordinate services for backups and migrations.
Using Active Storage, an application can transform image uploads or generate image representations of non-image uploads like PDFs and videos, and extract metadata from arbitrary files.
1.1 Requirements
Various features of Active Storage depend on third-party software which Rails will not install, and must be installed separately:
- libvips v8.6+ or ImageMagick for image analysis and transformations
- ffmpeg v3.4+ for video previews and ffprobe for video/audio analysis
- poppler or muPDF for PDF previews
Image analysis and transformations also require the image_processing
gem. Uncomment it in your Gemfile
, or add it if necessary:
gem "image_processing", ">= 1.2"
Compared to libvips, ImageMagick is better known and more widely available. However, libvips can be up to 10x faster and consume 1/10 the memory. For JPEG files, this can be further improved by replacing libjpeg-dev
with libjpeg-turbo-dev
, which is 2-7x faster.
Before you install and use third-party software, make sure you understand the licensing implications of doing so. MuPDF, in particular, is licensed under AGPL and requires a commercial license for some use.
2 Setup
$ bin/rails active_storage:install
$ bin/rails db:migrate
This sets up configuration, and creates the three tables Active Storage uses:
active_storage_blobs
, active_storage_attachments
, and active_storage_variant_records
.
Table | Purpose |
---|---|
active_storage_blobs |
Stores data about uploaded files, such as filename and content type. |
active_storage_attachments |
A polymorphic join table that connects your models to blobs. If your model's class name changes, you will need to run a migration on this table to update the underlying record_type to your model's new class name. |
active_storage_variant_records |
If variant tracking is enabled, stores records for each variant that has been generated. |
If you are using UUIDs instead of integers as the primary key on your models, you should set Rails.application.config.generators { |g| g.orm :active_record, primary_key_type: :uuid }
in a config file.
Declare Active Storage services in config/storage.yml
. For each service your
application uses, provide a name and the requisite configuration. The example
below declares three services named local
, test
, and amazon
:
local:
service: Disk
root: <%= Rails.root.join("storage") %>
test:
service: Disk
root: <%= Rails.root.join("tmp/storage") %>
# Use bin/rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
amazon:
service: S3
access_key_id: <%= Rails.application.credentials.dig(:aws, :access_key_id) %>
secret_access_key: <%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
bucket: your_own_bucket-<%= Rails.env %>
region: "" # e.g. 'us-east-1'
Tell Active Storage which service to use by setting
Rails.application.config.active_storage.service
. Because each environment will
likely use a different service, it is recommended to do this on a
per-environment basis. To use the disk service from the previous example in the
development environment, you would add the following to
config/environments/development.rb
:
# Store files locally.
config.active_storage.service = :local
To use the S3 service in production, you add the following to
config/environments/production.rb
:
# Store files on Amazon S3.
config.active_storage.service = :amazon
To use the test service when testing, you add the following to
config/environments/test.rb
:
# Store uploaded files on the local file system in a temporary directory.
config.active_storage.service = :test
Configuration files that are environment-specific will take precedence:
in production, for example, the config/storage/production.yml
file (if existent)
will take precedence over the config/storage.yml
file.
It is recommended to use Rails.env
in the bucket names to further reduce the risk of accidentally destroying production data.
amazon:
service: S3
# ...
bucket: your_own_bucket-<%= Rails.env %>
google:
service: GCS
# ...
bucket: your_own_bucket-<%= Rails.env %>
azure:
service: AzureStorage
# ...
container: your_container_name-<%= Rails.env %>
Continue reading for more information on the built-in service adapters (e.g.
Disk
and S3
) and the configuration they require.
2.1 Disk Service
Declare a Disk service in config/storage.yml
:
local:
service: Disk
root: <%= Rails.root.join("storage") %>
2.2 S3 Service (Amazon S3 and S3-compatible APIs)
To connect to Amazon S3, declare an S3 service in config/storage.yml
:
# Use bin/rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
amazon:
service: S3
access_key_id: <%= Rails.application.credentials.dig(:aws, :access_key_id) %>
secret_access_key: <%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
region: "" # e.g. 'us-east-1'
bucket: your_own_bucket-<%= Rails.env %>
Optionally provide client and upload options:
# Use bin/rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
amazon:
service: S3
access_key_id: <%= Rails.application.credentials.dig(:aws, :access_key_id) %>
secret_access_key: <%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
region: "" # e.g. 'us-east-1'
bucket: your_own_bucket-<%= Rails.env %>
http_open_timeout: 0
http_read_timeout: 0
retry_limit: 0
upload:
server_side_encryption: "" # 'aws:kms' or 'AES256'
cache_control: "private, max-age=<%= 1.day.to_i %>"
Set sensible client HTTP timeouts and retry limits for your application. In certain failure scenarios, the default AWS client configuration may cause connections to be held for up to several minutes and lead to request queuing.
Add the aws-sdk-s3
gem to your Gemfile
:
gem "aws-sdk-s3", require: false
The core features of Active Storage require the following permissions: s3:ListBucket
, s3:PutObject
, s3:GetObject
, and s3:DeleteObject
. Public access additionally requires s3:PutObjectAcl
. If you have additional upload options configured such as setting ACLs then additional permissions may be required.
If you want to use environment variables, standard SDK configuration files, profiles,
IAM instance profiles or task roles, you can omit the access_key_id
, secret_access_key
,
and region
keys in the example above. The S3 Service supports all of the
authentication options described in the AWS SDK documentation.
To connect to an S3-compatible object storage API such as DigitalOcean Spaces, provide the endpoint
:
digitalocean:
service: S3
endpoint: https://nyc3.digitaloceanspaces.com
access_key_id: <%= Rails.application.credentials.dig(:digitalocean, :access_key_id) %>
secret_access_key: <%= Rails.application.credentials.dig(:digitalocean, :secret_access_key) %>
# ...and other options
There are many other options available. You can check them in AWS S3 Client documentation.
2.3 Microsoft Azure Storage Service
Declare an Azure Storage service in config/storage.yml
:
# Use bin/rails credentials:edit to set the Azure Storage secret (as azure_storage:storage_access_key)
azure:
service: AzureStorage
storage_account_name: your_account_name
storage_access_key: <%= Rails.application.credentials.dig(:azure_storage, :storage_access_key) %>
container: your_container_name-<%= Rails.env %>
Add the azure-storage-blob
gem to your Gemfile
:
gem "azure-storage-blob", "~> 2.0", require: false
2.4 Google Cloud Storage Service
Declare a Google Cloud Storage service in config/storage.yml
:
google:
service: GCS
credentials: <%= Rails.root.join("path/to/keyfile.json") %>
project: ""
bucket: your_own_bucket-<%= Rails.env %>
Optionally provide a Hash of credentials instead of a keyfile path:
# Use bin/rails credentials:edit to set the GCS secrets (as gcs:private_key_id|private_key)
google:
service: GCS
credentials:
type: "service_account"
project_id: ""
private_key_id: <%= Rails.application.credentials.dig(:gcs, :private_key_id) %>
private_key: <%= Rails.application.credentials.dig(:gcs, :private_key).dump %>
client_email: ""
client_id: ""
auth_uri: "https://accounts.google.com/o/oauth2/auth"
token_uri: "https://accounts.google.com/o/oauth2/token"
auth_provider_x509_cert_url: "https://www.googleapis.com/oauth2/v1/certs"
client_x509_cert_url: ""
project: ""
bucket: your_own_bucket-<%= Rails.env %>
Optionally provide a Cache-Control metadata to set on uploaded assets:
google:
service: GCS
...
cache_control: "public, max-age=3600"
Optionally use IAM instead of the credentials
when signing URLs. This is useful if you are authenticating your GKE applications with Workload Identity, see this Google Cloud blog post for more information.
google:
service: GCS
...
iam: true
Optionally use a specific GSA when signing URLs. When using IAM, the metadata server will be contacted to get the GSA email, but this metadata server is not always present (e.g. local tests) and you may wish to use a non-default GSA.
google:
service: GCS
...
iam: true
gsa_email: "foobar@baz.iam.gserviceaccount.com"
Add the google-cloud-storage
gem to your Gemfile
:
gem "google-cloud-storage", "~> 1.11", require: false
2.5 Mirror Service
You can keep multiple services in sync by defining a mirror service. A mirror service replicates uploads and deletes across two or more subordinate services.
A mirror service is intended to be used temporarily during a migration between services in production. You can start mirroring to a new service, copy pre-existing files from the old service to the new, then go all-in on the new service.
Mirroring is not atomic. It is possible for an upload to succeed on the primary service and fail on any of the subordinate services. Before going all-in on a new service, verify that all files have been copied.
Define each of the services you'd like to mirror as described above. Reference them by name when defining a mirror service:
# Use bin/rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
s3_west_coast:
service: S3
access_key_id: <%= Rails.application.credentials.dig(:aws, :access_key_id) %>
secret_access_key: <%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
region: "" # e.g. 'us-west-1'
bucket: your_own_bucket-<%= Rails.env %>
s3_east_coast:
service: S3
access_key_id: <%= Rails.application.credentials.dig(:aws, :access_key_id) %>
secret_access_key: <%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
region: "" # e.g. 'us-east-1'
bucket: your_own_bucket-<%= Rails.env %>
production:
service: Mirror
primary: s3_east_coast
mirrors:
- s3_west_coast
Although all secondary services receive uploads, downloads are always handled by the primary service.
Mirror services are compatible with direct uploads. New files are directly uploaded to the primary service. When a directly-uploaded file is attached to a record, a background job is enqueued to copy it to the secondary services.
2.6 Public access
By default, Active Storage assumes private access to services. This means generating signed, single-use URLs for blobs. If you'd rather make blobs publicly accessible, specify public: true
in your app's config/storage.yml
:
gcs: &gcs
service: GCS
project: ""
private_gcs:
<<: *gcs
credentials: <%= Rails.root.join("path/to/private_key.json") %>
bucket: your_own_bucket-<%= Rails.env %>
public_gcs:
<<: *gcs
credentials: <%= Rails.root.join("path/to/public_key.json") %>
bucket: your_own_bucket-<%= Rails.env %>
public: true
Make sure your buckets are properly configured for public access. See docs on how to enable public read permissions for Amazon S3, Google Cloud Storage, and Microsoft Azure storage services. Amazon S3 additionally requires that you have the s3:PutObjectAcl
permission.
When converting an existing application to use public: true
, make sure to update every individual file in the bucket to be publicly-readable before switching over.
3 Attaching Files to Records
3.1 has_one_attached
The has_one_attached
macro sets up a one-to-one mapping between records and
files. Each record can have one file attached to it.
For example, suppose your application has a User
model. If you want each user to
have an avatar, define the User
model as follows:
class User < ApplicationRecord
has_one_attached :avatar
end
or if you are using Rails 6.0+, you can run a model generator command like this:
$ bin/rails generate model User avatar:attachment
You can create a user with an avatar:
<%= form.file_field :avatar %>
class SignupController < ApplicationController
def create
user = User.create!(user_params)
session[:user_id] = user.id
redirect_to root_path
end
private
def user_params
params.require(:user).permit(:email_address, :password, :avatar)
end
end
Call avatar.attach
to attach an avatar to an existing user:
user.avatar.attach(params[:avatar])
Call avatar.attached?
to determine whether a particular user has an avatar:
user.avatar.attached?
In some cases you might want to override a default service for a specific attachment.
You can configure specific services per attachment using the service
option with the name of your service:
class User < ApplicationRecord
has_one_attached :avatar, service: :google
end
You can configure specific variants per attachment by calling the variant
method on yielded attachable object:
class User < ApplicationRecord
has_one_attached :avatar do |attachable|
attachable.variant :thumb, resize_to_limit: [100, 100]
end
end
Call avatar.variant(:thumb)
to get a thumb variant of an avatar:
<%= image_tag user.avatar.variant(:thumb) %>
You can use specific variants for previews as well:
class User < ApplicationRecord
has_one_attached :video do |attachable|
attachable.variant :thumb, resize_to_limit: [100, 100]
end
end
<%= image_tag user.video.preview(:thumb) %>
If you know in advance that your variants will be accessed, you can specify that Rails should generate them ahead of time:
class User < ApplicationRecord
has_one_attached :video do |attachable|
attachable.variant :thumb, resize_to_limit: [100, 100], preprocessed: true
end
end
Rails will enqueue a job to generate the variant after the attachment is attached to the record.
Since Active Storage relies on polymorphic associations, and polymorphic associations rely on storing class names in the database, that data must remain synchronized with the class name used by the Ruby code. When renaming classes that use has_one_attached
, make sure to also update the class names in the active_storage_attachments.record_type
polymorphic type column of the corresponding rows.
3.2 has_many_attached
The has_many_attached
macro sets up a one-to-many relationship between records
and files. Each record can have many files attached to it.
For example, suppose your application has a Message
model. If you want each
message to have many images, define the Message
model as follows:
class Message < ApplicationRecord
has_many_attached :images
end
or if you are using Rails 6.0+, you can run a model generator command like this:
$ bin/rails generate model Message images:attachments
You can create a message with images:
class MessagesController < ApplicationController
def create
message = Message.create!(message_params)
redirect_to message
end
private
def message_params
params.require(:message).permit(:title, :content, images: [])
end
end
Call images.attach
to add new images to an existing message:
@message.images.attach(params[:images])
Call images.attached?
to determine whether a particular message has any images:
@message.images.attached?
Overriding the default service is done the same way as has_one_attached
, by using the service
option:
class Message < ApplicationRecord
has_many_attached :images, service: :s3
end
Configuring specific variants is done the same way as has_one_attached
, by calling the variant
method on the yielded attachable object:
class Message < ApplicationRecord
has_many_attached :images do |attachable|
attachable.variant :thumb, resize_to_limit: [100, 100]
end
end
Since Active Storage relies on polymorphic associations, and polymorphic associations rely on storing class names in the database, that data must remain synchronized with the class name used by the Ruby code. When renaming classes that use has_many_attached
, make sure to also update the class names in the active_storage_attachments.record_type
polymorphic type column of the corresponding rows.
3.3 Attaching File/IO Objects
Sometimes you need to attach a file that doesn’t arrive via an HTTP request. For example, you may want to attach a file you generated on disk or downloaded from a user-submitted URL. You may also want to attach a fixture file in a model test. To do that, provide a Hash containing at least an open IO object and a filename:
@message.images.attach(io: File.open('/path/to/file'), filename: 'file.pdf')
When possible, provide a content type as well. Active Storage attempts to determine a file’s content type from its data. It falls back to the content type you provide if it can’t do that.
@message.images.attach(io: File.open('/path/to/file'), filename: 'file.pdf', content_type: 'application/pdf')
You can bypass the content type inference from the data by passing in
identify: false
along with the content_type
.
@message.images.attach(
io: File.open('/path/to/file'),
filename: 'file.pdf',
content_type: 'application/pdf',
identify: false
)
If you don’t provide a content type and Active Storage can’t determine the file’s content type automatically, it defaults to application/octet-stream.
There is an additional parameter key
that can be used to specify folders/sub-folders
in your S3 Bucket. AWS S3 otherwise uses a random key to name your files. This
approach is helpful if you want to organize your S3 Bucket files better.
@message.images.attach(
io: File.open('/path/to/file'),
filename: 'file.pdf',
content_type: 'application/pdf',
key: "#{Rails.env}/blog_content/intuitive_filename.pdf",
identify: false
)
This way the file will get saved in the folder [S3_BUCKET]/development/blog_content/
when you test this from your development environment. Note that if you use the key
parameter, you have to ensure the key to be unique for the upload to go through. It is
recommended to append the filename with a unique random key, something like:
def s3_file_key
"#{Rails.env}/blog_content/intuitive_filename-#{SecureRandom.uuid}.pdf"
end
@message.images.attach(
io: File.open('/path/to/file'),
filename: 'file.pdf',
content_type: 'application/pdf',
key: s3_file_key,
identify: false
)
3.4 Replacing vs Adding Attachments
By default in Rails, attaching files to a has_many_attached
association will replace
any existing attachments.
To keep existing attachments, you can use hidden form fields with the signed_id
of each attached file:
<% @message.images.each do |image| %>
<%= form.hidden_field :images, multiple: true, value: image.signed_id %>
<% end %>
<%= form.file_field :images, multiple: true %>
This has the advantage of making it possible to remove existing attachments selectively, e.g. by using JavaScript to remove individual hidden fields.
3.5 Form Validation
Attachments aren't sent to the storage service until a successful save
on the
associated record. This means that if a form submission fails validation, any new
attachment(s) will be lost and must be uploaded again. Since direct uploads
are stored before the form is submitted, they can be used to retain uploads when validation fails:
<%= form.hidden_field :avatar, value: @user.avatar.signed_id if @user.avatar.attached? %>
<%= form.file_field :avatar, direct_upload: true %>
4 Removing Files
To remove an attachment from a model, call purge
on the
attachment. If your application is set up to use Active Job, removal can be done
in the background instead by calling purge_later
.
Purging deletes the blob and the file from the storage service.
# Synchronously destroy the avatar and actual resource files.
user.avatar.purge
# Destroy the associated models and actual resource files async, via Active Job.
user.avatar.purge_later
5 Serving Files
Active Storage supports two ways to serve files: redirecting and proxying.
All Active Storage controllers are publicly accessible by default. The generated URLs are hard to guess, but permanent by design. If your files require a higher level of protection consider implementing Authenticated Controllers.
5.1 Redirect Mode
To generate a permanent URL for a blob, you can pass the blob to the
url_for
view helper. This generates a
URL with the blob's signed_id
that is routed to the blob's RedirectController
url_for(user.avatar)
# => https://www.example.com/rails/active_storage/blobs/redirect/:signed_id/my-avatar.png
The RedirectController
redirects to the actual service endpoint. This
indirection decouples the service URL from the actual one, and allows, for
example, mirroring attachments in different services for high-availability. The
redirection has an HTTP expiration of 5 minutes.
To create a download link, use the rails_blob_{path|url}
helper. Using this
helper allows you to set the disposition.
rails_blob_path(user.avatar, disposition: "attachment")
To prevent XSS attacks, Active Storage forces the Content-Disposition header to "attachment" for some kind of files. To change this behavior see the available configuration options in Configuring Rails Applications.
If you need to create a link from outside of controller/view context (Background
jobs, Cronjobs, etc.), you can access the rails_blob_path
like this:
Rails.application.routes.url_helpers.rails_blob_path(user.avatar, only_path: true)
5.2 Proxy Mode
Optionally, files can be proxied instead. This means that your application servers will download file data from the storage service in response to requests. This can be useful for serving files from a CDN.
You can configure Active Storage to use proxying by default:
# config/initializers/active_storage.rb
Rails.application.config.active_storage.resolve_model_to_route = :rails_storage_proxy
Or if you want to explicitly proxy specific attachments there are URL helpers you can use in the form of rails_storage_proxy_path
and rails_storage_proxy_url
.
<%= image_tag rails_storage_proxy_path(@user.avatar) %>
5.2.1 Putting a CDN in Front of Active Storage
Additionally, in order to use a CDN for Active Storage attachments, you will need to generate URLs with proxy mode so that they are served by your app and the CDN will cache the attachment without any extra configuration. This works out of the box because the default Active Storage proxy controller sets an HTTP header indicating to the CDN to cache the response.
You should also make sure that the generated URLs use the CDN host instead of your app host. There are multiple ways to achieve this, but in general it involves tweaking your config/routes.rb
file so that you can generate the proper URLs for the attachments and their variations. As an example, you could add this:
# config/routes.rb
direct :cdn_image do |model, options|
expires_in = options.delete(:expires_in) { ActiveStorage.urls_expire_in }
if model.respond_to?(:signed_id)
route_for(
:rails_service_blob_proxy,
model.signed_id(expires_in: expires_in),
model.filename,
options.merge(host: ENV['CDN_HOST'])
)
else
signed_blob_id = model.blob.signed_id(expires_in: expires_in)
variation_key = model.variation.key
filename = model.blob.filename
route_for(
:rails_blob_representation_proxy,
signed_blob_id,
variation_key,
filename,
options.merge(host: ENV['CDN_HOST'])
)
end
end
and then generate routes like this:
<%= cdn_image_url(user.avatar.variant(resize_to_limit: [128, 128])) %>
5.3 Authenticated Controllers
All Active Storage controllers are publicly accessible by default. The generated
URLs use a plain signed_id
, making them hard to
guess but permanent. Anyone that knows the blob URL will be able to access it,
even if a before_action
in your ApplicationController
would otherwise
require a login. If your files require a higher level of protection, you can
implement your own authenticated controllers, based on the
ActiveStorage::Blobs::RedirectController
,
ActiveStorage::Blobs::ProxyController
,
ActiveStorage::Representations::RedirectController
and
ActiveStorage::Representations::ProxyController
To only allow an account to access their own logo you could do the following:
# config/routes.rb
resource :account do
resource :logo
end
# app/controllers/logos_controller.rb
class LogosController < ApplicationController
# Through ApplicationController:
# include Authenticate, SetCurrentAccount
def show
redirect_to Current.account.logo.url
end
end
<%= image_tag account_logo_path %>
And then you should disable the Active Storage default routes with:
config.active_storage.draw_routes = false
to prevent files being accessed with the publicly accessible URLs.
6 Downloading Files
Sometimes you need to process a blob after it’s uploaded—for example, to convert
it to a different format. Use the attachment's download
method to read a blob’s
binary data into memory:
binary = user.avatar.download
You might want to download a blob to a file on disk so an external program (e.g.
a virus scanner or media transcoder) can operate on it. Use the attachment's
open
method to download a blob to a tempfile on disk:
message.video.open do |file|
system '/path/to/virus/scanner', file.path
# ...
end
It's important to know that the file is not yet available in the after_create
callback but in the after_create_commit
only.
7 Analyzing Files
Active Storage analyzes files once they've been uploaded by queuing a job in Active Job. Analyzed files will store additional information in the metadata hash, including analyzed: true
. You can check whether a blob has been analyzed by calling analyzed?
on it.
Image analysis provides width
and height
attributes. Video analysis provides these, as well as duration
, angle
, display_aspect_ratio
, and video
and audio
booleans to indicate the presence of those channels. Audio analysis provides duration
and bit_rate
attributes.
8 Displaying Images, Videos, and PDFs
Active Storage supports representing a variety of files. You can call
representation
on an attachment to display an image variant, or a
preview of a video or PDF. Before calling representation
, check if the
attachment can be represented by calling representable?
. Some file formats
can't be previewed by Active Storage out of the box (e.g. Word documents); if
representable?
returns false you may want to link to
the file instead.
<ul>
<% @message.files.each do |file| %>
<li>
<% if file.representable? %>
<%= image_tag file.representation(resize_to_limit: [100, 100]) %>
<% else %>
<%= link_to rails_blob_path(file, disposition: "attachment") do %>
<%= image_tag "placeholder.png", alt: "Download file" %>
<% end %>
<% end %>
</li>
<% end %>
</ul>
Internally, representation
calls variant
for images, and preview
for
previewable files. You can also call these methods directly.
8.1 Lazy vs Immediate Loading
By default, Active Storage will process representations lazily. This code:
image_tag file.representation(resize_to_limit: [100, 100])
Will generate an <img>
tag with the src
pointing to the
ActiveStorage::Representations::RedirectController
. The browser will
make a request to that controller, which will perform the following:
- Process file and upload the processed file if necessary.
- Return a
302
redirect to the file either to- the remote service (e.g., S3).
- or
ActiveStorage::Blobs::ProxyController
which will return the file contents if proxy mode is enabled.
Loading the file lazily allows features like single use URLs to work without slowing down your initial page loads.
This works fine for most cases.
If you want to generate URLs for images immediately, you can call .processed.url
:
image_tag file.representation(resize_to_limit: [100, 100]).processed.url
The Active Storage variant tracker improves performance of this, by storing a
record in the database if the requested representation has been processed before.
Thus, the above code will only make an API call to the remote service (e.g. S3)
once, and once a variant is stored, will use that. The variant tracker runs
automatically, but can be disabled through config.active_storage.track_variants
.
If you're rendering lots of images on a page, the above example could result
in N+1 queries loading all the variant records. To avoid these N+1 queries,
use the named scopes on ActiveStorage::Attachment
.
message.images.with_all_variant_records.each do |file|
image_tag file.representation(resize_to_limit: [100, 100]).processed.url
end
8.2 Transforming Images
Transforming images allows you to display the image at your choice of dimensions.
To create a variation of an image, call variant
on the attachment. You
can pass any transformation supported by the variant processor to the method.
When the browser hits the variant URL, Active Storage will lazily transform
the original blob into the specified format and redirect to its new service
location.
<%= image_tag user.avatar.variant(resize_to_limit: [100, 100]) %>
If a variant is requested, Active Storage will automatically apply transformations depending on the image's format:
Content types that are variable (as dictated by
config.active_storage.variable_content_types
) and not considered web images (as dictated byconfig.active_storage.web_image_content_types
), will be converted to PNG.If
quality
is not specified, the variant processor's default quality for the format will be used.
Active Storage can use either Vips or MiniMagick as the variant processor.
The default depends on your config.load_defaults
target version, and the
processor can be changed by setting config.active_storage.variant_processor
.
The parameters available are defined by the image_processing
gem and depend on the
variant processor that you are using, but both support the following parameters:
Parameter | Example | Description |
---|---|---|
resize_to_limit |
resize_to_limit: [100, 100] |
Downsizes the image to fit within the specified dimensions while retaining the original aspect ratio. Will only resize the image if it's larger than the specified dimensions. |
resize_to_fit |
resize_to_fit: [100, 100] |
Resizes the image to fit within the specified dimensions while retaining the original aspect ratio. Will downsize the image if it's larger than the specified dimensions or upsize if it's smaller. |
resize_to_fill |
resize_to_fill: [100, 100] |
Resizes the image to fill the specified dimensions while retaining the original aspect ratio. If necessary, will crop the image in the larger dimension. |
resize_and_pad |
resize_and_pad: [100, 100] |
Resizes the image to fit within the specified dimensions while retaining the original aspect ratio. If necessary, will pad the remaining area with transparent color if source image has alpha channel, black otherwise. |
crop |
crop: [20, 50, 300, 300] |
Extracts an area from an image. The first two arguments are the left and top edges of area to extract, while the last two arguments are the width and height of the area to extract. |
rotate |
rotate: 90 |
Rotates the image by the specified angle. |
image_processing
has all parameters available in it's own documentation
for both the
Vips and
MiniMagick
processors.
Some parameters, including those listed above, accept additional processor
specific options which can be passed as key: value
pairs inside a hash:
<!-- Vips supports configuring `crop` for many of its transformations -->
<%= image_tag user.avatar.variant(resize_to_fill: [100, 100, { crop: :centre }]) %>
If migrating an existing application between MiniMagick and Vips, processor specific options will need to be updated:
<!-- MiniMagick -->
<%= image_tag user.avatar.variant(resize_to_limit: [100, 100], format: :jpeg, sampling_factor: "4:2:0", strip: true, interlace: "JPEG", colorspace: "sRGB", quality: 80) %>
<!-- Vips -->
<%= image_tag user.avatar.variant(resize_to_limit: [100, 100], format: :jpeg, saver: { subsample_mode: "on", strip: true, interlace: true, quality: 80 }) %>
8.3 Previewing Files
Some non-image files can be previewed: that is, they can be presented as images.
For example, a video file can be previewed by extracting its first frame. Out of
the box, Active Storage supports previewing videos and PDF documents. To create
a link to a lazily-generated preview, use the attachment's preview
method:
<%= image_tag message.video.preview(resize_to_limit: [100, 100]) %>
To add support for another format, add your own previewer. See the
ActiveStorage::Preview
documentation for more information.
9 Direct Uploads
Active Storage, with its included JavaScript library, supports uploading directly from the client to the cloud.
9.1 Usage
Include
activestorage.js
in your application's JavaScript bundle.Using the asset pipeline:
//= require activestorage
Using the npm package:
import * as ActiveStorage from "@rails/activestorage" ActiveStorage.start()
Add
direct_upload: true
to your file field:<%= form.file_field :attachments, multiple: true, direct_upload: true %>
Or, if you aren't using a
FormBuilder
, add the data attribute directly:<input type="file" data-direct-upload-url="<%= rails_direct_uploads_url %>" />
Configure CORS on third-party storage services to allow direct upload requests.
That's it! Uploads begin upon form submission.
9.2 Cross-Origin Resource Sharing (CORS) Configuration
To make direct uploads to a third-party service work, you’ll need to configure the service to allow cross-origin requests from your app. Consult the CORS documentation for your service:
Take care to allow:
- All origins from which your app is accessed
- The
PUT
request method - The following headers:
Content-Type
Content-MD5
Content-Disposition
(except for Azure Storage)x-ms-blob-content-disposition
(for Azure Storage only)x-ms-blob-type
(for Azure Storage only)Cache-Control
(for GCS, only ifcache_control
is set)
No CORS configuration is required for the Disk service since it shares your app’s origin.
9.2.1 Example: S3 CORS Configuration
[
{
"AllowedHeaders": [
"Content-Type",
"Content-MD5",
"Content-Disposition"
],
"AllowedMethods": [
"PUT"
],
"AllowedOrigins": [
"https://www.example.com"
],
"MaxAgeSeconds": 3600
}
]
9.2.2 Example: Google Cloud Storage CORS Configuration
[
{
"origin": ["https://www.example.com"],
"method": ["PUT"],
"responseHeader": ["Content-Type", "Content-MD5", "Content-Disposition"],
"maxAgeSeconds": 3600
}
]
9.2.3 Example: Azure Storage CORS Configuration
<Cors>
<CorsRule>
<AllowedOrigins>https://www.example.com</AllowedOrigins>
<AllowedMethods>PUT</AllowedMethods>
<AllowedHeaders>Content-Type, Content-MD5, x-ms-blob-content-disposition, x-ms-blob-type</AllowedHeaders>
<MaxAgeInSeconds>3600</MaxAgeInSeconds>
</CorsRule>
</Cors>
9.3 Direct Upload JavaScript Events
Event name | Event target | Event data (event.detail ) |
Description |
---|---|---|---|
direct-uploads:start |
<form> |
None | A form containing files for direct upload fields was submitted. |
direct-upload:initialize |
<input> |
{id, file} |
Dispatched for every file after form submission. |
direct-upload:start |
<input> |
{id, file} |
A direct upload is starting. |
direct-upload:before-blob-request |
<input> |
{id, file, xhr} |
Before making a request to your application for direct upload metadata. |
direct-upload:before-storage-request |
<input> |
{id, file, xhr} |
Before making a request to store a file. |
direct-upload:progress |
<input> |
{id, file, progress} |
As requests to store files progress. |
direct-upload:error |
<input> |
{id, file, error} |
An error occurred. An alert will display unless this event is canceled. |
direct-upload:end |
<input> |
{id, file} |
A direct upload has ended. |
direct-uploads:end |
<form> |
None | All direct uploads have ended. |
9.4 Example
You can use these events to show the progress of an upload.
To show the uploaded files in a form:
// direct_uploads.js
addEventListener("direct-upload:initialize", event => {
const { target, detail } = event
const { id, file } = detail
target.insertAdjacentHTML("beforebegin", `
<div id="direct-upload-${id}" class="direct-upload direct-upload--pending">
<div id="direct-upload-progress-${id}" class="direct-upload__progress" style="width: 0%"></div>
<span class="direct-upload__filename"></span>
</div>
`)
target.previousElementSibling.querySelector(`.direct-upload__filename`).textContent = file.name
})
addEventListener("direct-upload:start", event => {
const { id } = event.detail
const element = document.getElementById(`direct-upload-${id}`)
element.classList.remove("direct-upload--pending")
})
addEventListener("direct-upload:progress", event => {
const { id, progress } = event.detail
const progressElement = document.getElementById(`direct-upload-progress-${id}`)
progressElement.style.width = `${progress}%`
})
addEventListener("direct-upload:error", event => {
event.preventDefault()
const { id, error } = event.detail
const element = document.getElementById(`direct-upload-${id}`)
element.classList.add("direct-upload--error")
element.setAttribute("title", error)
})
addEventListener("direct-upload:end", event => {
const { id } = event.detail
const element = document.getElementById(`direct-upload-${id}`)
element.classList.add("direct-upload--complete")
})
Add styles:
/* direct_uploads.css */
.direct-upload {
display: inline-block;
position: relative;
padding: 2px 4px;
margin: 0 3px 3px 0;
border: 1px solid rgba(0, 0, 0, 0.3);
border-radius: 3px;
font-size: 11px;
line-height: 13px;
}
.direct-upload--pending {
opacity: 0.6;
}
.direct-upload__progress {
position: absolute;
top: 0;
left: 0;
bottom: 0;
opacity: 0.2;
background: #0076ff;
transition: width 120ms ease-out, opacity 60ms 60ms ease-in;
transform: translate3d(0, 0, 0);
}
.direct-upload--complete .direct-upload__progress {
opacity: 0.4;
}
.direct-upload--error {
border-color: red;
}
input[type=file][data-direct-upload-url][disabled] {
display: none;
}
9.5 Custom drag and drop solutions
You can use the DirectUpload
class for this purpose. Upon receiving a file from your library
of choice, instantiate a DirectUpload and call its create method. Create takes
a callback to invoke when the upload completes.
import { DirectUpload } from "@rails/activestorage"
const input = document.querySelector('input[type=file]')
// Bind to file drop - use the ondrop on a parent element or use a
// library like Dropzone
const onDrop = (event) => {
event.preventDefault()
const files = event.dataTransfer.files;
Array.from(files).forEach(file => uploadFile(file))
}
// Bind to normal file selection
input.addEventListener('change', (event) => {
Array.from(input.files).forEach(file => uploadFile(file))
// you might clear the selected files from the input
input.value = null
})
const uploadFile = (file) => {
// your form needs the file_field direct_upload: true, which
// provides data-direct-upload-url
const url = input.dataset.directUploadUrl
const upload = new DirectUpload(file, url)
upload.create((error, blob) => {
if (error) {
// Handle the error
} else {
// Add an appropriately-named hidden input to the form with a
// value of blob.signed_id so that the blob ids will be
// transmitted in the normal upload flow
const hiddenField = document.createElement('input')
hiddenField.setAttribute("type", "hidden");
hiddenField.setAttribute("value", blob.signed_id);
hiddenField.name = input.name
document.querySelector('form').appendChild(hiddenField)
}
})
}
9.6 Track the progress of the file upload
When using the DirectUpload
constructor, it is possible to include a third parameter.
This will allow the DirectUpload
object to invoke the directUploadWillStoreFileWithXHR
method during the upload process.
You can then attach your own progress handler to the XHR to suit your needs.
import { DirectUpload } from "@rails/activestorage"
class Uploader {
constructor(file, url) {
this.upload = new DirectUpload(file, url, this)
}
uploadFile(file) {
this.upload.create((error, blob) => {
if (error) {
// Handle the error
} else {
// Add an appropriately-named hidden input to the form
// with a value of blob.signed_id
}
})
}
directUploadWillStoreFileWithXHR(request) {
request.upload.addEventListener("progress",
event => this.directUploadDidProgress(event))
}
directUploadDidProgress(event) {
// Use event.loaded and event.total to update the progress bar
}
}
9.7 Integrating with Libraries or Frameworks
Once you receive a file from the library you have selected, you need to create
a DirectUpload
instance and use its "create" method to initiate the upload process,
adding any required additional headers as necessary. The "create" method also requires
a callback function to be provided that will be triggered once the upload has finished.
import { DirectUpload } from "@rails/activestorage"
class Uploader {
constructor(file, url, token) {
const headers = { 'Authentication': `Bearer ${token}` }
// INFO: Sending headers is an optional parameter. If you choose not to send headers,
// authentication will be performed using cookies or session data.
this.upload = new DirectUpload(file, url, this, headers)
}
uploadFile(file) {
this.upload.create((error, blob) => {
if (error) {
// Handle the error
} else {
// Use the with blob.signed_id as a file reference in next request
}
})
}
directUploadWillStoreFileWithXHR(request) {
request.upload.addEventListener("progress",
event => this.directUploadDidProgress(event))
}
directUploadDidProgress(event) {
// Use event.loaded and event.total to update the progress bar
}
}
To implement customized authentication, a new controller must be created on the Rails application, similar to the following:
class DirectUploadsController < ActiveStorage::DirectUploadsController
skip_forgery_protection
before_action :authenticate!
def authenticate!
@token = request.headers['Authorization']&.split&.last
head :unauthorized unless valid_token?(@token)
end
end
Using Direct Uploads can sometimes result in a file that uploads, but never attaches to a record. Consider purging unattached uploads.
10 Testing
Use file_fixture_upload
to test uploading a file in an integration or controller test.
Rails handles files like any other parameter.
class SignupController < ActionDispatch::IntegrationTest
test "can sign up" do
post signup_path, params: {
name: "David",
avatar: file_fixture_upload("david.png", "image/png")
}
user = User.order(:created_at).last
assert user.avatar.attached?
end
end
10.1 Discarding Files Created During Tests
10.1.1 System Tests
System tests clean up test data by rolling back a transaction. Because destroy
is never called on an object, the attached files are never cleaned up. If you
want to clear the files, you can do it in an after_teardown
callback. Doing it
here ensures that all connections created during the test are complete and
you won't receive an error from Active Storage saying it can't find a file.
class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
# ...
def after_teardown
super
FileUtils.rm_rf(ActiveStorage::Blob.service.root)
end
# ...
end
If you're using parallel tests and the DiskService
, you should configure each process to use its own
folder for Active Storage. This way, the teardown
callback will only delete files from the relevant process'
tests.
class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
# ...
parallelize_setup do |i|
ActiveStorage::Blob.service.root = "#{ActiveStorage::Blob.service.root}-#{i}"
end
# ...
end
If your system tests verify the deletion of a model with attachments and you're using Active Job, set your test environment to use the inline queue adapter so the purge job is executed immediately rather at an unknown time in the future.
# Use inline job processing to make things happen immediately
config.active_job.queue_adapter = :inline
10.1.2 Integration Tests
Similarly to System Tests, files uploaded during Integration Tests will not be
automatically cleaned up. If you want to clear the files, you can do it in an
teardown
callback.
class ActionDispatch::IntegrationTest
def after_teardown
super
FileUtils.rm_rf(ActiveStorage::Blob.service.root)
end
end
If you're using parallel tests and the Disk service, you should configure each process to use its own
folder for Active Storage. This way, the teardown
callback will only delete files from the relevant process'
tests.
class ActionDispatch::IntegrationTest
parallelize_setup do |i|
ActiveStorage::Blob.service.root = "#{ActiveStorage::Blob.service.root}-#{i}"
end
end
10.2 Adding Attachments to Fixtures
You can add attachments to your existing fixtures. First, you'll want to create a separate storage service:
# config/storage.yml
test_fixtures:
service: Disk
root: <%= Rails.root.join("tmp/storage_fixtures") %>
This tells Active Storage where to "upload" fixture files to, so it should be a temporary directory. By making it
a different directory to your regular test
service, you can separate fixture files from files uploaded during a
test.
Next, create fixture files for the Active Storage classes:
# active_storage/attachments.yml
david_avatar:
name: avatar
record: david (User)
blob: david_avatar_blob
# active_storage/blobs.yml
david_avatar_blob: <%= ActiveStorage::FixtureSet.blob filename: "david.png", service_name: "test_fixtures" %>
Then put a file in your fixtures directory (the default path is test/fixtures/files
) with the corresponding filename.
See the ActiveStorage::FixtureSet
docs for more information.
Once everything is set up, you'll be able to access attachments in your tests:
class UserTest < ActiveSupport::TestCase
def test_avatar
avatar = users(:david).avatar
assert avatar.attached?
assert_not_nil avatar.download
assert_equal 1000, avatar.byte_size
end
end
10.2.1 Cleaning up Fixtures
While files uploaded in tests are cleaned up at the end of each test, you only need to clean up fixture files once: when all your tests complete.
If you're using parallel tests, call parallelize_teardown
:
class ActiveSupport::TestCase
# ...
parallelize_teardown do |i|
FileUtils.rm_rf(ActiveStorage::Blob.services.fetch(:test_fixtures).root)
end
# ...
end
If you're not running parallel tests, use Minitest.after_run
or the equivalent for your test
framework (e.g. after(:suite)
for RSpec):
# test_helper.rb
Minitest.after_run do
FileUtils.rm_rf(ActiveStorage::Blob.services.fetch(:test_fixtures).root)
end
10.3 Configuring services
You can add config/storage/test.yml
to configure services to be used in test environment
This is useful when the service
option is used.
class User < ApplicationRecord
has_one_attached :avatar, service: :s3
end
Without config/storage/test.yml
, the s3
service configured in config/storage.yml
is used - even when running tests.
The default configuration would be used and files would be uploaded to the service provider configured in config/storage.yml
.
In this case, you can add config/storage/test.yml
and use Disk service for s3
service to prevent sending requests.
test:
service: Disk
root: <%= Rails.root.join("tmp/storage") %>
s3:
service: Disk
root: <%= Rails.root.join("tmp/storage") %>
11 Implementing Support for Other Cloud Services
If you need to support a cloud service other than these, you will need to
implement the Service. Each service extends
ActiveStorage::Service
by implementing the methods necessary to upload and download files to the cloud.
12 Purging Unattached Uploads
There are cases where a file is uploaded but never attached to a record. This can happen when using Direct Uploads. You can query for unattached records using the unattached scope. Below is an example using a custom rake task.
namespace :active_storage do
desc "Purges unattached Active Storage blobs. Run regularly."
task purge_unattached: :environment do
ActiveStorage::Blob.unattached.where(created_at: ..2.days.ago).find_each(&:purge_later)
end
end
The query generated by ActiveStorage::Blob.unattached
can be slow and potentially disruptive on applications with larger databases.
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