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ADR-004: Realtime Data Channels

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Abstract

The fundamental communication component across all Sonr nodes is the channel. By utilizing data and transport agnostic realtime streams between nodes, we effectively have realtime structured data transmission at any point in the world.

Primer

The Sonr channel implementation requires prior knowledge of the following definitions before implementation.

multiaddr

Multiaddr's are self describing addresses that operate on any network protocol. They provide human-readable and efficient machine-readable representations. The multiaddr spec by protocol labs provides further details about the mechanism.

pub-sub

The Sonr implementation follows the standard publish/subscribe model present with the modern web, with the caveat that it operates on a peer-to-peer node. In particular, Sonr utilizes the gossip-sub implementation specification to manage sending messages between peers on the network.

Service endpoint

A Service endpoint describes a url which is associated to the did.

Topic

A Topic is a series of contexts which are denoted by '/' these contexts are heigharical and facilitate routing of data.

Temporary Channel

A temporary channel is a channel that exists between two Peers on the Sonr network. This channel exists for as long as the application which defines it keeps the channel active. Once the channel is deactivated it is destroyed. Messages passed between the two Peers are not persistent in this mode. Temporary Channels communicate on specified topics and utilize the Exchange model within Sonr.

Persistent Channel

A persistent channel is a channel which mirrors the implementation of a Temporary Channel but has more functionality.

  • A Schema is defined for the data sent between two Peers
  • On creation, a new Bucket is created for the channel
  • Data published on the channel is also stored in the Channel's bucket

Objective

  • An Open transport agnostic communication mechanism
  • Accessibility for users to listen to channels based on application
  • A mechanism for developers to create channels for their individual development needs
  • Structured Object reperesentation as the payload body between messages, as specified in ADR-002

Addressing & Identifiying Topics

In Sonr, the name of a channel follows the multiaddr specification for individual protocols that operate for a specific application. When resolving a DIDDocument of a particular application, developers are also provided a list of channels present for the application under its Service endpoint property.

Topics

Topics in the Sonr channel mechanism are defined as Developer created persistent stream endpoints where users can join and are always ensured to return pre-defined structured data, as per ADR-002.

Topic Name Representation

/sonr/channels/[applicationName]/[version]/[topicName]

Example Topic Identifier

/sonr/channels/beam/v1/SonrGroupChat

Protocols

Protocols in the Sonr channel mechanism are defined as having pre-packaged spec-compliant functionality, accessible to both users to interact and developers to leverage. For example one of the provided core protocols by the Sonr Team is our Libp2p Matrix Integration.

Client Side Interaction (Ephemeral Channels)

Description

The Client side, or Motor implementation of Channels utilizes the Sonr exchange protocol. Exchange protocol is in charge of routing messages between Peers. The methods defined in the below section wrap the Exchange protcol in order to implement described functionality.

Relationship between Channel instance and Topics

Each channel Object created is for a single topic each topic is then associated with that channel for both publishing and listening on topics.

Methods

The following methods are provided by Sonr's client-side Motor package, to be leveraged by frontends powered by the Sonr ecosystem.

Listen()

topicName : string

When a channel has succesfully been routed and verified, the client is returned a Channel definition this facilitates communication on the specified topic when other Peers that are also Listening on the given Topic

Publish()

topicName : string

body : buffer

Calling a post method to the endpoint results in the client posting a message to the underlying PubSub topic. The message will successfully publish to the channel if the provided body message correctly maps to the DID and object reference involved with the channel.

Channels on chain (Persistent Channel Definitions)

Description

Persistent channels have the same behavior of Ephemeral changes. When said channel is created the following record is stored on chain.

Models

who is model

HowIs {
// Did is the DID of the channel
Did: string
// Document is the DID Document of the registered name and account encoded as JSON
Creator: string
// ChannelDoc is the structure of the channel encoded as JSON
Channel: ChannelDoc
// Timestamp is the time of the last update of the DID Document
Timestamp int64
// Is Active is the status of the DID Document
IsActive bool
}
// options is a collection of options for the beam.
options {
ttl: time.Duration
capacity: int
}

Channel X modle interface definition Definition

// Channel is a pubsub based Key-Value store for Libp2p nodes.
Channel {
// Did returns the DID of the channel.
Did() string

// Read returns a list of all peers subscribed to the channel topic.
Read() []peer.ID

// Publish publishes the given message to the channel topic.
Publish(obj *ot.ObjectDoc) error

// Listen subscribes to the beam topic and returns a channel that will
// receive events.
Listen(opChan chan *ChannelMessage)

// Close closes the channel.
Close() error
}

Document Schema and applications

A Schema is defined when the Persistant channel is created. Creation of said channel will create a Transaction on chain. only persistant channels use this mechanism.

CreateChannel

Parameters

Creator : string

Label : string

Description : string

RegisteredObject : ObjectDoc

Creates a new Channel definition for an application. The method requires the DID of the application or user, a label for human-readable representation, description for the functionality of the channel, and a registered object for defining what structured data is returned by the channel.

When the channel is created, the created object is set to Listening as side effect.

Response

{
type : "tx/MsgCreateChannel",
body: {
"code": 200,
"did": "did:snr:abc123",
"channel": {
"label": "test",
"description": "A example channel",
"registeredObject": [...] // See ADR-002
}
}
}

UpdateChannel

Parameters

Creator : string

Label : string (optional)

Description : string (optional)

RegisteredObject : sonrio.sonr.object.ObjectDoc (optional)

Updates a Channel's information, all data is optional for update. However, the entire object document must be updated as that is considered a single property in this model.

Response

{
type : "tx/MsgUpdateChannel",
body: {
"code": 200,
"did": "did:snr:abc123",
"channel": {
"label": "test",
"description": "A example channel",
"registeredObject": [...] // See ADR-002
}
}
}

DeactivateChannel

creator: : DID of the creator of the channel.

label : A human readable label to assign to the channel.

Utilized by developers to effectively eliminate any existing structured channel representation for a given application. A record will be created on change flagging the isActive property to false. Denoting the channel is no longer active.

Response

{
type : "tx/MsgDeleteChannel",
body: {
"code": 200,
"did": "did:snr:abc123",
}
}

Sequence Diagrams


References