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diff --git a/guides/source/active_storage_overview.md b/guides/source/active_storage_overview.md new file mode 100644 index 0000000000..d9f5aa8385 --- /dev/null +++ b/guides/source/active_storage_overview.md @@ -0,0 +1,565 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.** + +Active Storage Overview +======================= + +This guide covers how to attach files to your Active Record models. + +After reading this guide, you will know: + +* How to attach one or many files to a record. +* How to delete an attached file. +* How to link to an attached file. +* How to use variants to transform images. +* How to generate an image representation of a non-image file, such as a PDF or a video. +* How to send file uploads directly from browsers to a storage service, + bypassing your application servers. +* How to clean up files stored during testing. +* How to implement support for additional storage services. + +-------------------------------------------------------------------------------- + +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 with +[ImageMagick](https://www.imagemagick.org), generate image representations of +non-image uploads like PDFs and videos, and extract metadata from arbitrary +files. + +## Setup + +Active Storage uses two tables in your application’s database named +`active_storage_blobs` and `active_storage_attachments`. After upgrading your +application to Rails 5.2, run `rails active_storage:install` to generate a +migration that creates these tables. Use `rails db:migrate` to run the +migration. + +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`: + +```yaml +local: + service: Disk + root: <%= Rails.root.join("storage") %> + +test: + service: Disk + root: <%= Rails.root.join("tmp/storage") %> + +amazon: + service: S3 + access_key_id: "" + secret_access_key: "" +``` + +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`: + +```ruby +# Store files locally. +config.active_storage.service = :local +``` + +To use the Amazon S3 service in production, you add the following to +`config/environments/production.rb`: + +```ruby +# Store files on Amazon S3. +config.active_storage.service = :amazon +``` + +Continue reading for more information on the built-in service adapters (e.g. +`Disk` and `S3`) and the configuration they require. + +### Disk Service + +Declare a Disk service in `config/storage.yml`: + +```yaml +local: + service: Disk + root: <%= Rails.root.join("storage") %> +``` + +Optionally specify a host for generating URLs (the default is `http://localhost:3000`): + +```yaml +local: + service: Disk + root: <%= Rails.root.join("storage") %> + host: http://myapp.test +``` + +### Amazon S3 Service + +Declare an S3 service in `config/storage.yml`: + +```yaml +amazon: + service: S3 + access_key_id: "" + secret_access_key: "" + region: "" + bucket: "" +``` + +Add the [`aws-sdk-s3`](https://github.com/aws/aws-sdk-ruby) gem to your `Gemfile`: + +```ruby +gem "aws-sdk-s3", require: false +``` + +### Microsoft Azure Storage Service + +Declare an Azure Storage service in `config/storage.yml`: + +```yaml +azure: + service: AzureStorage + path: "" + storage_account_name: "" + storage_access_key: "" + container: "" +``` + +Add the [`azure-storage`](https://github.com/Azure/azure-storage-ruby) gem to your `Gemfile`: + +```ruby +gem "azure-storage", require: false +``` + +### Google Cloud Storage Service + +Declare a Google Cloud Storage service in `config/storage.yml`: + +```yaml +google: + service: GCS + credentials: <%= Rails.root.join("path/to/keyfile.json") %> + project: "" + bucket: "" +``` + +Optionally provide a Hash of credentials instead of a keyfile path: + +```yaml +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) %> + 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: "" +``` + +Add the [`google-cloud-storage`](https://github.com/GoogleCloudPlatform/google-cloud-ruby/tree/master/google-cloud-storage) gem to your `Gemfile`: + +```ruby +gem "google-cloud-storage", "~> 1.3", require: false +``` + +### Mirror Service + +You can keep multiple services in sync by defining a mirror service. When a file +is uploaded or deleted, it's done across all the mirrored services. Mirrored +services can be used to facilitate a migration between services in production. +You can start mirroring to the new service, copy existing files from the old +service to the new, then go all-in on the new service. Define each of the +services you'd like to use as described above and reference them from a mirrored +service. + +```yaml +s3_west_coast: + service: S3 + access_key_id: "" + secret_access_key: "" + region: "" + bucket: "" + +s3_east_coast: + service: S3 + access_key_id: "" + secret_access_key: "" + region: "" + bucket: "" + +production: + service: Mirror + primary: s3_east_coast + mirrors: + - s3_west_coast +``` + +NOTE: Files are served from the primary service. + +Attaching Files to Records +-------------------------- + +### `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 like this: + +```ruby +class User < ApplicationRecord + has_one_attached :avatar +end +``` + +You can create a user with an avatar: + +```ruby +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: + +```ruby +Current.user.avatar.attach(params[:avatar]) +``` + +Call `avatar.attached?` to determine whether a particular user has an avatar: + +```ruby +Current.user.avatar.attached? +``` + +### `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 like this: + +```ruby +class Message < ApplicationRecord + has_many_attached :images +end +``` + +You can create a message with images: + +```ruby +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: + +```ruby +@message.images.attach(params[:images]) +``` + +Call `images.attached?` to determine whether a particular message has any images: + +```ruby +@message.images.attached? +``` + +Removing Files +-------------- + +To remove an attachment from a model, call `purge` on the attachment. Removal +can be done in the background if your application is setup to use Active Job. +Purging deletes the blob and the file from the storage service. + +```ruby +# 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 +``` + +Linking to Files +---------------- + +Generate a permanent URL for the blob that points to the application. Upon +access, a redirect to the actual service endpoint is returned. This indirection +decouples the public 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 min. + +```ruby +url_for(user.avatar) +``` + +To create a download link, use the `rails_blob_{path|url}` helper. Using this +helper allows you to set the disposition. + +```ruby +rails_blob_path(user.avatar, disposition: "attachment") +``` + +Transforming Images +------------------- + +To create variation of the image, call `variant` on the Blob. +You can pass any [MiniMagick](https://github.com/minimagick/minimagick) +supported transformation to the method. + +To enable variants, add `mini_magick` to your `Gemfile`: + +```ruby +gem 'mini_magick' +``` + +When the browser hits the variant URL, Active Storage will lazy transform the +original blob into the format you specified and redirect to its new service +location. + +```erb +<%= image_tag user.avatar.variant(resize: "100x100") %> +``` + +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. + +```erb +<ul> + <% @message.files.each do |file| %> + <li> + <%= image_tag file.preview(resize: "100x100>") %> + </li> + <% end %> +</ul> +``` + +WARNING: Extracting previews requires third-party applications, `ffmpeg` for +video and `mutool` for PDFs. These libraries are not provided by Rails. You must +install them yourself to use the built-in previewers. Before you install and use +third-party software, make sure you understand the licensing implications of +doing so. + +Direct Uploads +-------------- + +Active Storage, with its included JavaScript library, supports uploading +directly from the client to the cloud. + +### Direct upload installation + +1. Include `activestorage.js` in your application's JavaScript bundle. + + Using the asset pipeline: + + ```js + //= require activestorage + + ``` + + Using the npm package: + + ```js + import * as ActiveStorage from "activestorage" + ActiveStorage.start() + ``` + +2. Annotate file inputs with the direct upload URL. + + ```ruby + <%= form.file_field :attachments, multiple: true, direct_upload: true %> + ``` +3. That's it! Uploads begin upon form submission. + +### 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. | + +### Example + +You can use these events to show the progress of an upload. + + + +To show the uploaded files in a form: + +```js +// 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">${file.name}</span> + </div> + `) +}) + +addEventListener("direct-upload:start", event => { + const { id } = event.detail + const element = document.getElementById(`direct-upload-${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: + +```css +/* 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; +} +``` + +Discarding Files Stored During 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. + +```ruby +class ApplicationSystemTestCase < ActionDispatch::SystemTestCase + driven_by :selenium, using: :chrome, screen_size: [1400, 1400] + + def remove_uploaded_files + FileUtils.rm_rf("#{Rails.root}/storage_test") + end + + def after_teardown + super + remove_uploaded_files + 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. + +You may also want to use a separate service definition for the test environment +so your tests don't delete the files you create during development. + +```ruby +# Use inline job processing to make things happen immediately +config.active_job.queue_adapter = :inline + +# Separate file storage in the test environment +config.active_storage.service = :local_test +``` + +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`](https://github.com/rails/rails/blob/master/activestorage/lib/active_storage/service.rb) +by implementing the methods necessary to upload and download files to the cloud. |