gitlab-org--gitlab-foss/doc/development/file_storage.md

File Storage in GitLab

We use the CarrierWave gem to handle file upload, store and retrieval.

There are many places where file uploading is used, according to contexts:

• System
  • Instance Logo (logo visible in sign in/sign up pages)
  • Header Logo (one displayed in the navigation bar)
• Group
  • Group avatars
• User
  • User avatars
  • User snippet attachments
• Project
  • Project avatars
  • Issues/MR/Notes Markdown attachments
  • Issues/MR/Notes Legacy Markdown attachments
  • CI Artifacts (archive, metadata, trace)
  • LFS Objects

Disk storage

GitLab started saving everything on local disk. While directory location changed from previous versions, they are still not 100% standardized. You can see them below:

Description	In DB?	Relative path (from CarrierWave.root)	Uploader class	model_type
Instance logo	yes	uploads/-/system/appearance/logo/:id/:filename	AttachmentUploader	Appearance
Header logo	yes	uploads/-/system/appearance/header_logo/:id/:filename	AttachmentUploader	Appearance
Group avatars	yes	uploads/-/system/group/avatar/:id/:filename	AvatarUploader	Group
User avatars	yes	uploads/-/system/user/avatar/:id/:filename	AvatarUploader	User
User snippet attachments	yes	uploads/-/system/personal_snippet/:id/:random_hex/:filename	PersonalFileUploader	Snippet
Project avatars	yes	uploads/-/system/project/avatar/:id/:filename	AvatarUploader	Project
Issues/MR/Notes Markdown attachments	yes	uploads/:project_path_with_namespace/:random_hex/:filename	FileUploader	Project
Issues/MR/Notes Legacy Markdown attachments	no	uploads/-/system/note/attachment/:id/:filename	AttachmentUploader	Note
CI Artifacts (CE)	yes	shared/artifacts/:disk_hash[0..1]/:disk_hash[2..3]/:disk_hash/:year_:month_:date/:job_id/:job_artifact_id (:disk_hash is SHA256 digest of project_id)	JobArtifactUploader	Ci::JobArtifact
LFS Objects (CE)	yes	shared/lfs-objects/:hex/:hex/:object_hash	LfsObjectUploader	LfsObject

CI Artifacts and LFS Objects behave differently in CE and EE. In CE they inherit the GitlabUploader while in EE they inherit the ObjectStorage and store files in and S3 API compatible object store.

In the case of Issues/MR/Notes Markdown attachments, there is a different approach using the Hashed Storage layout, instead of basing the path into a mutable variable :project_path_with_namespace, it's possible to use the hash of the project ID instead, if project migrates to the new approach (introduced in 10.2).

Path segments

Files are stored at multiple locations and use different path schemes. All the GitlabUploader derived classes should comply with this path segment schema:

|   GitlabUploader
| ----------------------- + ------------------------- + --------------------------------- + -------------------------------- |
| `<gitlab_root>/public/` | `uploads/-/system/`       | `user/avatar/:id/`                | `:filename`                      |
| ----------------------- + ------------------------- + --------------------------------- + -------------------------------- |
| `CarrierWave.root`      | `GitlabUploader.base_dir` | `GitlabUploader#dynamic_segment`  | `CarrierWave::Uploader#filename` |
|                         | `CarrierWave::Uploader#store_dir`                             |                                  | 

|   FileUploader
| ----------------------- + ------------------------- + --------------------------------- + -------------------------------- |
| `<gitlab_root>/shared/` | `artifacts/`              | `:year_:month/:id`                | `:filename`                      |
| `<gitlab_root>/shared/` | `snippets/`               | `:secret/`                        | `:filename`                      |
| ----------------------- + ------------------------- + --------------------------------- + -------------------------------- |
| `CarrierWave.root`      | `GitlabUploader.base_dir` | `GitlabUploader#dynamic_segment`  | `CarrierWave::Uploader#filename` |
|                         | `CarrierWave::Uploader#store_dir`                             |                                  | 
|                         |                           | `FileUploader#upload_path                                            |

|   ObjectStore::Concern (store = remote)
| ----------------------- + ------------------------- + ----------------------------------- + -------------------------------- |
| `<bucket_name>`         | <ignored>                 | `user/avatar/:id/`                  | `:filename`                      |
| ----------------------- + ------------------------- + ----------------------------------- + -------------------------------- |
| `#fog_dir`              | `GitlabUploader.base_dir` | `GitlabUploader#dynamic_segment`    | `CarrierWave::Uploader#filename` |
|                         |                           | `ObjectStorage::Concern#store_dir`  |                                  | 
|                         |                           | `ObjectStorage::Concern#upload_path                                    |

The RecordsUploads::Concern concern will create an Upload entry for every file stored by a GitlabUploader persisting the dynamic parts of the path using GitlabUploader#dynamic_path. You may then use the Upload#build_uploader method to manipulate the file.

Object Storage

By including the ObjectStorage::Concern in the GitlabUploader derived class, you may enable the object storage for this uploader. To enable the object storage in your uploader, you need to either 1) include RecordsUpload::Concern and prepend ObjectStorage::Extension::RecordsUploads or 2) mount the uploader and create a new field named <mount>_store.

The CarrierWave::Uploader#store_dir is overriden to

• GitlabUploader.base_dir + GitlabUploader.dynamic_segment when the store is LOCAL
• GitlabUploader.dynamic_segment when the store is REMOTE (the bucket name is used to namespace)

Using ObjectStorage::Extension::RecordsUploads

Note: this concern will automatically include RecordsUploads::Concern if not already included.

The ObjectStorage::Concern uploader will search for the matching Upload to select the correct object store. The Upload is mapped using #store_dirs + identifier for each store (LOCAL/REMOTE).

class SongUploader < GitlabUploader
  include RecordsUploads::Concern
  include ObjectStorage::Concern
  prepend ObjectStorage::Extension::RecordsUploads

  ...
end

class Thing < ActiveRecord::Base
  mount :theme, SongUploader # we have a great theme song!

  ...
end

Using a mounted uploader

The ObjectStorage::Concern will query the model.<mount>_store attribute to select the correct object store. This column must be present in the model schema.

class SongUploader < GitlabUploader
  include ObjectStorage::Concern

  ...
end

class Thing < ActiveRecord::Base
  attr_reader :theme_store # this is an ActiveRecord attribute
  mount :theme, SongUploader # we have a great theme song!

  def theme_store
    super || ObjectStorage::Store::LOCAL
  end

  ...
end