File uploading with Shrine gem

RRUG #10 - 9.11.2017

Przemek Sienkowski

Ruby Developer

What is Shrine?

  • Alternative for (CarrierWave, Refile, Paperclip, ...)
  • Combine their advantages and functionalities
  • Shrine implements a plugin system
  • Flexibility - configurable differently depending on what types of files are being uploaded
  • Simplicity

Shrine advantages

  • build-in support for AWS S3
  • direct upload
  • backgrounding
  • validation helpers
  • determining MIME type
  • ActiveRecord and Sequel support
  • automatically back up stored files to an additional storage
  • copying attachment between two records
  • ...

Components parts

  • Storage - object responsible for managing files on a specific storage service
  • Plugin -  load the code only for features that you need
  • Uploader
  • Attacher

My experiences with Shrine

The goal was to achieve followed behaviours:

  1. Files should be uploaded on AWS S3 for staging and productions.
  2. Direct upload from the FE application to S3 should be possible.
  3. Upload from the URL should be possible with handling validation errors about incorrect/unreachable URL.
  4. Upload should be done in the background.

Gem installation & configuration

# Gemfile

gem 'shrine'
gem 'aws-sdk-s3'
# config/initializers/shrine.rb

require 'shrine'
require "shrine/storage/s3"
 
s3_options = {
  access_key_id:     Rails.application.secrets.s3_access_key_id,
  secret_access_key: Rails.application.secrets.s3_secret_access_key,
  region:            Rails.application.secrets.s3_region,
  bucket:            Rails.application.secrets.s3_bucket
}

Shrine.storages = {
  cache: Shrine::Storage::S3.new(prefix: "cache", **s3_options),
  store: Shrine::Storage::S3.new(prefix: "store", **s3_options)
}

Shrine.plugin :activerecord

What about test and development?

group :test do
  gem 'shrine-memory'
end
# config/initializers/shrine.rb
require 'shrine'
if Rails.env.development?
  require "shrine/storage/file_system"
  Shrine.storages = {
    cache: Shrine::Storage::FileSystem.new("public", prefix: "uploads/cache"),
    store: Shrine::Storage::FileSystem.new("public", prefix: "uploads/store")
  }
elsif Rails.env.test?
  require 'shrine/storage/memory'
  Shrine.storages = {
    cache: Shrine::Storage::Memory.new,
    store: Shrine::Storage::Memory.new
  }
else
  require "shrine/storage/s3"
  s3_options = {
    access_key_id:     Rails.application.secrets.s3_access_key_id,
    secret_access_key: Rails.application.secrets.s3_secret_access_key,
    region:            Rails.application.secrets.s3_region,
    bucket:            Rails.application.secrets.s3_bucket
  }

  Shrine.storages = {
    cache: Shrine::Storage::S3.new(prefix: "cache", **s3_options),
    store: Shrine::Storage::S3.new(prefix: "store", **s3_options)
  }
end

Shrine.plugin :activerecord

Linking the uploader

class AddFileDataToAttachments < ActiveRecord::Migration
  def change
    add_column :attachments, :file_data, :text
  end
end
# app/uploaders/attachment.rb
require 'shrine/plugins/determine_mime_type'

class AttachmentUploader < Shrine
  plugin :determine_mime_type
end
# app/models/attachment.rb

class Attachment < ApplicationRecord
  include AttachmentUploader.attachment(:file)
end

Flow of file uploading

  1. FE application sends request to presign URL, which will be used to upload file directly from the FE application to the S3.
  2. BE application responds with JSON, which contains data required to authenticating with S3 and uploading a file.
  3. FE uploads the file to temporary location by using data from the previous step.
  4. FE generates JSON with cached on the S3 file and sends it to the BE.
  5. BE updating a record in the database and move file between "cache" storage to "store".

Pre-signing endpoint

# config/initializers/shrine.rb

# ...

Shrine.plugin :presign_endpoint
# config/routes.rb

Rails.application.routes.draw do
  mount Shrine.presign_endpoint(:cache) => "/presign"
end

Pre-signing endpoint

{
    "url": "https://bucket-name.s3.eu-central-1.amazonaws.com",
    "fields": {
        "key": "cache/2084783353bf6e5fdfe3420b8bff3a8c.pdf",
        "policy": "eyJleHBpcmF0aW9uIjoiMjAxNy0xMC0xOVQwODoxMDowkaXRpb25...BaIn1dfQ==",
        "x-amz-credential": "AKIAJZNAKLVM1ADO124A/20171019/eu-central-1/s3/aws4_request",
        "x-amz-algorithm": "AWS4-HMAC-SHA256",
        "x-amz-date": "20171019T071000Z",
        "x-amz-signature": "19c31571fb1031d64bed4c31eecc2bf5fe5737855z4378a640326d6061114714"
    },
    "headers": {}
}

GET /presign?filename=file.pdf

It's enough to upload file directly on the S3.

What's with development?

# lib/attachments/storage/presigned_file_system.rb
require 'shrine/storage/file_system'

class Attachments::Storage::PresignedFileSystem < Shrine::Storage::FileSystem
  include Rails.application.routes.url_helpers
  PresignedPost = Struct.new(:url, :fields)

  def presign(*_args)
    url = URI::HTTP.build(
      host: Rails::Server.new.options[:Host],
      port: Rails::Server.new.options[:Port],
      path: api_v1_attachment_uploader_upload_endpoint_path + '/cache/upload'
    ).to_s
    PresignedPost.new(url, {})
  end
end
# config/initializers/shrine.rb

require 'shrine'

if Rails.env.development?
  Shrine.storages = {
    cache: Attachments::Storage::PresignedFileSystem.new("public", prefix: "uploads/cache"),
    store: Attachments::Storage::PresignedFileSystem.new("public", prefix: "uploads/store")
  }
elsif Rails.env.test?
  # ...
else
  # ...
end
# ...

What's with development?

{
    "url": "http://localhost:3000/attachments/cache/upload",
    "fields": {},
    "headers": {}
}

GET /presign?filename=file.pdf

What's with development?

# app/uploaders/attachment.rb

require 'shrine/plugins/upload_endpoint'

class AttachmentUploader < Shrine
  # ...
  plugin :upload_endpoint
end
# config/routes.rb

Rails.application.routes.draw do
  mount Shrine.presign_endpoint(:cache) => "/presign"
  if %w(development test).include?(Rails.env)
    mount AttachmentUploader.upload_endpoint(:cache) => "/attachments"
  end
end

File data

{
  "id": "2084783353bf6e5fdfe3420b8bff3a8c.pdf",
  "storage": "cache",
  "metadata": {
    "filename": "example.pdf",
    "size": 1024,
    "mime_type": "application/pdf"
  }
}
a = Attachment.new(file: file_data)
a.file
# => #<AttachmentUploader::UploadedFile:0x007f80db3f9590
#    @data={"id"=>"2084783353bf6e5fdfe3420b8bff3a8c.pdf", "storage"=>"cache",
#           "metadata"=>{"filename"=>"file.pdf", "size"=>1024, "mime_type"=>"application/pdf"}}>


a.save
a.reload.file
# => #<AttachmentUploader::UploadedFile:0x007f8f0d74dcd8
#    @data={"id"=>"504e412892b9e869136abe645e15e3c8.pdf", "storage"=>"store",
#           "metadata"=>{"filename"=>"file.pdf", "size"=>1024, "mime_type"=>"application/pdf"}}>

Cache cleaning

Backgrounding

# config/application.rb

# ...
class Application < Rails::Application
  config.active_job.queue_adapter = :sidekiq

  # ...
end
# config/initializers/shrine.rb

# ...
Shrine.plugin :backgrounding

Backgrounding

# app/jobs/promote_job.rb
class PromoteJob < ActiveJob::Base
  def perform(data)
    Shrine::Attacher.promote(data)
  end
end
# app/jobs/delete_job.rb
class DeleteJob < ActiveJob::Base
  def perform(data)
    Shrine::Attacher.delete(data)
  end
end
# app/uploaders/attachment.rb
class AttachmentUploader < Shrine
  # ...
  Attacher.promote { |data| PromoteJob.perform_later(data) }
  Attacher.delete { |data| DeleteJob.perform_later(data) }
end

Uploading from URL

# Gemfile
gem 'shrine-url'
{
  id: 'http://example.com/example.pdf',
  storage: 'cache',
  metadata: { ... }
}

`remote_url` plugin isn't proper choose

It provides additional storage class. The main idea of this gem is storing file data like below:

How choose storage dynamically?

Shrine.storages = {
 cache: Shrine::Storage::S3.new(prefix: "cache", **s3_options),
 store: Shrine::Storage::S3.new(prefix: "store", **s3_options)
}

We want to have possibilities to keep 2 object as cache storage implementation.

current storage configuration:

default_storage & dynamic_storage plugins

# app/uploaders/attachment.rb
class AttachmentUploader < Shrine
  # ...
  plugin :dynamic_storage
  storage /cache_(\w+)/ do |match|
    match[1] == 'url' ? Attachments::Storage::Url.new : Shrine.storages[:cache]
  end
  
  plugin :default_storage, cache: lambda { |record, _name|
    id = JSON.parse(record.file_data || {}.to_json)['id']
    id =~ URI::regexp(['http', 'https']) ? :cache_url : :cache
   }
end

default_storage & dynamic_storage plugins

# app/uploaders/attachment.rb
class AttachmentUploader < Shrine
  # ...
  plugin :dynamic_storage
  storage /cache_(\w+)/ do |match|
    match[1] == 'url' ? Attachments::Storage::Url.new : Shrine.storages[:cache]
  end
  
  plugin :default_storage, cache: lambda { |record, _name|
    id = JSON.parse(record.file_data || {}.to_json)['id']
    id =~ URI::regexp(['http', 'https']) ? :cache_url : :cache
   }
end

but it will not work :(

default_storage & dynamic_storage plugins

1.

{
  id: 'http://example.com/example.pdf',
  storage: 'cache_url',
  metadata: { ... }
}

2.

# app/uploaders/attachment.rb
class AttachmentUploader < Shrine
  # ...
  
  def uploaded?(uploaded_file)
    uploaded_file.storage_key.match(storage_key.to_s) ||
      storage_key.to_s.match(uploaded_file.storage_key)
  end
end

After that the file uploading to local system storage worked properly, but issue for Shrine on GH has ben reported.

New way to selecting storages dynamically

{
  id: 'http://example.com/example.pdf',
  storage: 'cache_url',
  metadata: { ... }
}
cache_type = JSON.parse(file_data)['storage'])
attachment.file_attacher(cache: cache_type)
attachment.file = file_data
# config/initializers/shrine.rb
# ...

Shrine.storages[:cache_url] = Shrine::Storage::Url.new

Both of ways doesn't work for S3 storage

# lib/attachments/storage/s3_with_remoteable.rb
require "shrine/storage/s3"

class Attachments::Storage::S3WithRemoteable < Shrine::Storage::S3
  def put(io, id, **options)
    return super unless io.is_a?(AttachmentUploader::UploadedFile) &&
                        defined?(Shrine::Storage::Url) &&
                        io.storage.is_a?(Shrine::Storage::Url)
    io.open do |body|
      object(id).put(body: body, **options)
    end
  end
end
# config/initializers/shrine.rb
if Rails.env.development?
  # ...
elsif Rails.env.test?
  # ...
else
  s3_options = { ... }
  Shrine.storages = {
    cache: Attachments::Storage::S3WithRemoteable.new(prefix: "cache", **s3_options),
    store: Attachments::Storage::S3WithRemoteable.new(prefix: "store", **s3_options)
   }
end

Unfortunately the storage class for S3 does not support copying from the URL

Assigning remote file

# app/model/attachment.rb
# ...

def file_remote_url=(value)
  return if value.nil?
  remote_file = Attachments::RemoteFile.new(value, file_attacher)
  self.file = remote_file.file_data.to_json
end

def file=(value)
 set_file_cache_dynamically(value)
 super
end

def set_file_cache_dynamically(file_data)
  file_attacher(cache: JSON.parse(file_data)['storage'])
rescue JSON::ParserError => _e
  file_attacher(cache: 'cache')
end

Validation of URL correctness and reachability

# lib/attachments/storage/url.rb
require "shrine/storage/url"

class Attachments::Storage::Url < Shrine::Storage::Url
class IncorrectUrlError < StandardError; end
  def fetch_metadata(id)
    raise IncorrectUrlError unless id =~ URI::regexp(['http', 'https'])
    request(:head, id)
  rescue SocketError, URI::InvalidURIError => e
    raise IncorrectUrlError.new(e)
  end
end
# config/initializers/shrine.rb
# ...

Shrine.storages[:cache_url] = Attachments::Storage::Url.new

Fetching metadata

# lib/attachments/remote_file.rb
class Attachments::RemoteFile
  STORAGE_NAME = :cache_url
  Metadata = Struct.new(:filename, :size, :mime_type) do
    def initialize(filename = nil, size = 0, mime_type = nil)
      super
    end
  end
      
  attr_reader :url, :attacher, :incorrect_url
      
  def initialize(url, attacher)
    @url = url
    @attacher = attacher
    @incorrect_url = false
  end
      
  def file_name
    path = URI.parse(url).path
    File.basename(path)
  end
      
  def file_data
    {
      id: url,
      storage: STORAGE_NAME,
      metadata: metadata
    }
  end
      
  def correct_url?
    !incorrect_url
  end
   
  private

  def metadata
    @metadata ||= fetch_metadata
  end
      
  def fetch_metadata
    unless head_response.is_a? Net::HTTPSuccess
      report_incorrect_url!
    end
    Metadata.new(
      file_name,
      head_response.content_length,
      head_response.content_type
    ).to_h
  rescue Attachments::Storage::Url::IncorrectUrlError =>_e
    report_incorrect_url!
    Metadata.new.to_h
  end
      
  def uploader_class
    @attacher.store.class
  end
      
  def storage
    @storage ||= uploader_class.find_storage(STORAGE_NAME)
  end
      
  def head_response
    @head_response ||= storage.fetch_metadata(url)
  end
      
  def report_incorrect_url!
    @incorrect_url = true
  end
end

Thanks

File uploading with Shrine gem

By Przemek Sienkowski

File uploading with Shrine gem

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