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Funkwhale federation

Note

We aim to keep this document up-to-date to reflect the current state of federation. If you notice an issue, please open a thread on our forum.

Funkwhale is a federated platform. Funkwhale pods can share information between one another, and can also communicate with other Fediverse software. This article outlines which tools we use, our approach to federation, and how we implement standards.

Technologies and standards 

Funkwhale’s federation is built on top of the following technologies:

ActivityPub: Our federation protocol
HTTP Signatures: A library for authenticating messages sent over the federation
Webfinger: A protocol for discovering resources using readable names
ActivityStreams and ActivityStreams vocabulary: Our approach to structuring messages

We plan for support JSON-LD signatures in the future as an alternative to HTTP Signatures.

Our philosophy 

Funkwhale aims to align with the above specifications where possible to maintain compatibility with other ActivityPub-aware platforms. This documentation covers where we have departed from the specifications.

While we will always aim for compatibility with other services where it makes sense, Funkwhale to Funkwhale interaction is our focus. We use these standards to support activities and objects that fit in with our use cases, such as follows and likes.

Internal logic 

This section covers how we handle federation within the Funkwhale ecosystem.

Database schema 

We use ActivityPub entities as a guide when creating our models and database schemas. This ensures compatibility with other ActivityPub projects.

Funkwhale pods store received activities payloads in the database before attempting to process or deliver them. This enables us to debug federation issues, resend messages, or process historical activities that weren’t previously supported.

Funkwhale users are associated to an Actor. Remote and local actors are stord in the same database table. Any federated entities, such as uploads, are linked to the Actor rather than the user. We don’t distinguish between local and remote users on the database level.

Activity creation and delivery 

Any action carried out by a local actor should trigger an Activity. This is the equivalent to posting an activity to an object. Funkwhale creates an object with the activity payload and stores it in the Activity table. Funkwhale triggers 2 types of deliveries:

Local recipients: Funkwhale creates an InboxItem linked to the activity for each local recipient. Funkwhale then creates a feed of available inbox items for each local actor. Items in this feed have both a Read and Unread status to allow users to mark items as handled.
Remote recipients: Funkwhale collects the inboxes and shared inbox URLs of all remote recipients. Funkwhale then creates a Delivery object and linked to the initial activity and the inbox or shared inbox URL. The worker uses this Delivery object to post the activity to the correct inbox.

When a local inbox receives an activity from a remote actor, it ends up in their inbox for them to handle.

Funkwhale doesn’t support all activities. Our routing logic enables the software to handle supported activities and discard unsupported ones. When Funkwhale receives an activity it checks if there is a route to handle it. If there is, Funkwhale calls a dedicated handler.

For example: if Funkwhale receives an activity-create activity for an object-audio object, Funkwhale calls a handler to:

Persist the data in the local Upload table
Retrieve data associated with the audio

You can find the code for our routing logic here:

Service actor 

Funkwhale uses a dedicated service actor to send messages or authenticate fetches. This actor isn’t associated to a user.

You can query a pod’s nodeinfo endpoint to return the ID of the service actor in the metadata > actorId field. See the API explorer for more information about this endpoint.

Funkwhale considers a pod’s service actor to be an authoritative source for activities associated with all objects on its pod’s domain. If the service actor sends an activity linked to an object on its domain, remote pods will recognize its authority.

Supported activities 

Follow 

A follow enables actors to access and retrieve content from other actors as soon as it updates.

Internal logic

When Funkwhale receives a follow on a library object, it performs one of the following actions depending on the library’s visibility:

Automatically accept: If the library is public, Funkwhale automatically accepts the follow activity. Funkwhale sends a notification to the owner of the library and an Accept activity to the actor who sent the follow
Accept request: If the library isn’t public, Funkwhale sends a notification to the library owner. If the owner approves the request, Funkwhale sends an Accept activity to the actor who sent the follow

Funkwhale uses the library follow status to grant access to the actor who sent the follow request. If the library isn’t public and the owner doesn’t send an approval, the requesting actor can’t access the library’s content.

Checks

Funkwhale ensures the activity is being sent to the library’s owner before handling it.

Example

In this example, Alice sends a follow activity for a library object owned by Bob.

{
  "@context": [
      "https://www.w3.org/ns/activitystreams",
      "https://w3id.org/security/v1",
      {}
  ],
  "type": "Follow",
  "id": "https://music.rocks/federation/actors/Alice#follows/99fc40d7-9bc8-4c4a-add1-f637339e1ded",
  "actor": "https://music.rocks/federation/actors/Alice",
  "to": ["https://awesome.music/federation/actors/Bob"],
  "object": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6"
}

Accept 

The Accept activity sends a positive response, such as confirming a Follow activity.

Internal logic

When Funkwhale receives an Accept activity related to a Follow activity, it marks the Follow as accepted in the database. If the Follow activity relates to a Library object, the requester receives future activities associated with the library. This includes Create, Audio, and Delete activities. They can also browse and download the library’s audio files. See the section on Audio fetching on restricted libraries for more details.

Checks

Funkwhale ensures the activity is sent by the library’s owner before handling it.

Example

In this example, Bob accepts a follow request from Alice.

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
    {}
  ],
  "type": "Accept",
  "id": "https://music.rocks/federation/actors/Alice#follows/99fc40d7-9bc8-4c4a-add1-f637339e1ded/accept",
  "to": ["https://music.rocks/federation/actors/Alice"],
  "actor": "https://awesome.music/federation/actors/Bob",
  "object": {
    "id": "https://music.rocks/federation/actors/Alice#follows/99fc40d7-9bc8-4c4a-add1-f637339e1ded",
    "type": "Follow",
    "actor": "https://music.rocks/federation/actors/Alice",
    "object": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6",
  },
}

Undo 

Internal logic

When Funkwhale receives an Undo activity, it deletes the corresponding Follow from the database.

Checks

Funkwhale ensures the request actor is the same actor who sent the Follow activity before handling it.

Example

In this example, Alice notifies Bob that she’s undoing her follow.

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
    {}
  ],
  "type": "Undo",
  "id": "https://music.rocks/federation/actors/Alice#follows/99fc40d7-9bc8-4c4a-add1-f637339e1ded/accept",
  "to": ["https://awesome.music/federation/actors/Bob"],
  "actor": "https://music.rocks/federation/actors/Alice",
  "object": {
    "id": "https://music.rocks/federation/actors/Alice#follows/99fc40d7-9bc8-4c4a-add1-f637339e1ded",
    "type": "Follow",
    "actor": "https://music.rocks/federation/actors/Alice",
    "object": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6",
  },
}

Create 

Internal logic

Note

See the Audio object reference for details on the object’s structure.

When Funkwhale receives a Create activity with an Audio object, it persists a local upload in the database. It then associates the upload to related library and track information. If no track matches the audio metadata, Funkwhale creates on using the metadata attribute in the object.

Checks

Funkwhale ensures the activity actor and library owner are the same before handling the activity. If the associated library has no local followers, Funkwhale discards the activity.

Example

In this example, Bob creates new content in his library and sends a message to its followers.

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
    {}
  ],
  "to": [
    "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6/followers"
  ],
  "type": "Create",
  "actor": "https://awesome.music/federation/actors/Bob",
  "object": {}
}

Update 

Internal logic

Note

See the Track object reference and Library object reference for details on the object’s structure.

When Funkwhale receives an update associated with a Library or Track object, it attempts to update the corresponding object in its database.

Checks

Funkwhale performs different checks depending on the target of the update:

For Library objects, Funkwhale ensures the actor sending the message is the library owner
For Track objects, Funkwhale ensures the actor sending the message either:
- Matches the attributedTo property on the local copy of the object
- Is the service actor

Example

In this example, Bob updates his library and sends a message to its followers.

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
    {}
  ],
  "to": [
    "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6/followers"
  ],
  "type": "Update",
  "actor": "https://awesome.music/federation/actors/Bob",
  "object": {}
}

Delete 

Internal logic

When Funkwhale receives a Delete activity, it deletes the associated object from the database.

Checks

Funkwhale ensures the actor initiating the activity is the owner of the associated object before handling it.

Example

Library

In this example, Bob deletes a library and notifies its followers.

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
    {}
  ],
  "type": "Delete",
  "to": [
    "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6/followers"
  ],
  "actor": "https://awesome.music/federation/actors/Bob",
  "object": {
    "type": "Library",
    "id": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6"
  }
}

Audio

In this example, Bob deletes three audio objects in a library and notifies the library’s followers.

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
    {}
  ],
  "type": "Delete",
  "to": [
    "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6/followers"
  ],
  "actor": "https://awesome.music/federation/actors/Bob",
  "object": {
    "type": "Audio",
    "id": [
      "https://awesome.music/federation/music/uploads/19420073-3572-48a9-8c6c-b385ee1b7905",
      "https://awesome.music/federation/music/uploads/11d99680-23c6-4f72-997a-073b980ab204",
      "https://awesome.music/federation/music/uploads/1efadc1c-a704-4b8a-a71a-b288b1d1f423"
    ]
  }
}

Supported objects 

Artist 

An Artist is a custom object used to store musical artist and podcast creator information.

Properties

Property	Data type	Description
`type`*	String	The object type (`Artist`)
`id`*	String (URI)	A URI that identifies the artist over federation
`name`*	String	The artist’s name
`published`*	Datetime	The date on which the artist was published over the federation
`musicbrainzId`	String (UUID)	The Musicbrainz artist ID

Example

{
  "type": "Artist",
  "id": "https://awesome.music/federation/music/artists/73c32807-a199-4682-8068-e967f734a320",
  "name": "Metallica",
  "published": "2018-04-08T12:19:05.920415+00:00",
  "musicbrainzId": "65f4f0c5-ef9e-490c-aee3-909e7ae6b2ab"
}

Album 

An Album is a custom object used to store album and podcast series information.

Properties

Property	Data type	Description
`type`*	String	The object type (`Album`)
`id`*	String (URI)	A URI that identifies the album over federation
`name`*	String	The album’s title
`artists`	Array of strings	A list of `Artist` objects associated with the albums
`published`*	Datetime	The date on which the artist was published over the federation
`released`	Datetime	The date on which the album was released
`musicbrainzId`	String (UUID)	The Musicbrainz release ID
`cover`	`Link` object	A `Link` object representing the album cover

Example

{
  "type": "Album",
  "id": "https://awesome.music/federation/music/albums/69d488b5-fdf6-4803-b47c-9bb7098ea57e",
  "name": "Ride the Lightning",
  "released": "1984-01-01",
  "published": "2018-10-02T19:49:17.412546+00:00",
  "musicbrainzId": "589ff96d-0be8-3f82-bdd2-299592e51b40",
  "cover": {
    "href": "https://awesome.music/media/albums/covers/2018/10/02/b69d398b5-fdf6-4803-b47c-9bb7098ea57e.jpg",
    "type": "Link",
    "mediaType": "image/jpeg"
  },
  "artists": [
    {}
  ]
}

Track 

A Track is a custom object used to store track information.

Properties

Property	Data type	Description
`type`*	String	The object type (`Track`)
`id`*	String (URI)	A URI that identifies the track over federation
`name`*	String	The track title
`position`*	Integer	The position of the track in the album
`published`*	Datetime	The date on which the track was published over the federation
`musicbrainzId`	String (UUID)	The Musicbrainz recording ID
`album`	`Album` object	The album that contains the track
`artists`	Array of `Artist` objects	A list of artists associated to the track. This can differ from the album artists

Example

{
  "type": "Track",
  "id": "https://awesome.music/federation/music/tracks/82ece296-6397-4e26-be90-bac5f9990240",
  "name": "For Whom the Bell Tolls",
  "position": 3,
  "published": "2018-10-02T19:49:35.822537+00:00",
  "musicbrainzId": "771ab043-8821-44f9-b8e0-2733c3126c6d",
  "artists": [
    {}
  ],
  "album": {}
}

Library 

Note

Crawling library pages requires authentication and an approved follow unless the library is public.

A Library is a custom object used to store music collection information. It inherits its behavior and properties from ActivityPub’s Actor and Collection objects.

Properties

Property	Data type	Description
`type`*	String	The object type (`Library`)
`id`*	String (URI)	A URI that identifies the library over federation
`name`*	String	The library’s name
`followers`*	String (URI)	The ID of the library’s followers collection
`totalItems`*	Integer	The number of `Audio` objects in the library
`first`*	String (URI)	The URL of the library’s first page
`last`*	String (URI)	The URL of the library’s last page
`summary`	String	The library’s description

Example

{
  "type": "Library",
  "id": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6",
  "attributedTo": "https://awesome.music/federation/actors/Alice",
  "name": "My awesome library",
  "followers": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6/followers",
  "summary": "This library is for restricted use only",
  "totalItems": 4234,
  "first": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6?page=1",
  "last": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6?page=56",
}

Audio 

Note

Accessing audio files requires authentication and an approved follow for the containing library unless the library is public.

An Audio object is a custom object used to store upload information. It extends the ActivityStreams Audio object with custom attributes.

Properties

Property	Data type	Description
`type`*	String	The object type (`Audio`)
`id`*	String (URI)	A URI that identifies the audio over federation
`name`*	String	A readable title for the order. Funkwhale concatenates the track name, album title, and artist name
`size`*	Integer	The size of the audio in bytes
`bitrate`*	Integer	The bitrate of the audio in bytes/s
`duration`*	Integer	The duration of the audio in seconds
`library`*	String (URI)	The ID of the audio’s containing `Library` object
`published`*	Datetime	The date on which the audio was published over the federation
`updated`*	Datetime	The date on which the audio was last updated over the federation
`url`*	`Link` object	A `Link` object object containing the download location of the audio file
`track`	`Track` object	The track associated with the audio file

Example

{
  "type": "Audio",
  "id": "https://awesome.music/federation/music/uploads/88f0bc20-d7fd-461d-a641-dd9ac485e096",
  "name": "For Whom the Bell Tolls - Ride the Lightning - Metallica",
  "size": 8656581,
  "bitrate": 320000,
  "duration": 213,
  "library": "https://awesome.music/federation/music/libraries/dc702491-f6ce-441b-9da0-cecbed08bcc6",
  "updated": "2018-10-02T19:49:35.646372+00:00",
  "published": "2018-10-02T19:49:35.646359+00:00",
  "track": {},
  "url": {
    "href": "https://awesome.music/api/v1/listen/82ece296-6397-4e26-be90-bac5f9990240/?upload=88f0bc20-d7fd-461d-a641-dd9ac485e096",
    "type": "Link",
    "mediaType": "audio/mpeg"
  }
}

Audio fetching on restricted libraries 

Library objects and [Audio objects] are subject to the following access rules:

Library

Public libraries can be accessed by actors without restriction
Restricted libraries can only be accessed if the HTTP request is signed by an actor who has an associated approved Follow activity

Audio

Audio items in public libraries can be accessed by actors without restriction
Audio items in restricted libraries can only be accessed if the HTTP request is signed by an actor who has an associated approved Follow activity

Custom properties 

attributedTo 

Funkwhale uses the attributedTo property to denote the actor responsible for an object. If an object has an attributedTo attributed, the associated actor can perform activities to it, including Update and Delete.

Funkwhale also attributes all objects on a domain with the domain’s Service actor