Enum svc_agent::Destination

pub enum Destination {
    Broadcast(String),
    Multicast(AccountId, String),
    Unicast(AgentId, String),
}

Message destination.

This is an abstraction over MQTT topic pattern to determine outgoing message’s publish topic.

Understanding message routing is the key thing to use svc-agent. Make sure that you understand the patterns below and their counterparts described in Source.

MQTT topic variables:

• MY_ACCOUNT_ID – AccountId of the current agent that sends the message.
• MY_VER – API version string of the current agent. For example: v1.
• MY_BROADCAST_URI– current agent’s API specific path to some resource divided by /. For example: /rooms/ROOM_ID/events. If you will want to change its structure in the future you must also bump VER(ME).
• ACCOUNT_ID – destination AccountId (no specific agent).
• AGENT_ID – destination AgentId.
• VER – destination agent version.

Variants

Broadcast(String)

Publish a message to each of the topic subscribers.

Typically being used for publishing notification events from a service.

The string supplied is MY_BROADCAST_URI.

Patterns

Type	Pattern	MQTT topic
event	app-to-any	apps/MY_ACCOUNT_ID/api/MY_VER/MY_BROADCAST_URI

Multicast(AccountId, String)

Publish a message to any single of SharedGroup agents.

Typically being used for sending requests to services which may have multiple instances.

AccountId is being supplied since we don’t care which specific instance will process the message.

Patterns

Type	Pattern	MQTT topic
request	one-to_app	agents/MY_AGENT_ID/api/MY_VER/out/ACCOUNT_ID

Unicast(AgentId, String)

Publish a message to the specific instance with known AGENT_ID.

Typically being used for responding to requests. Also used for making a request to a specific instance of a stateful service.

Values supplied are AGENT_ID and VER.

Patterns

Type	Pattern	MQTT topic
request	one-to-one	agents/AGENT_ID/api/VER/in/MY_ACCOUNT_ID
response	one-to_one	agents/AGENT_ID/api/VER/in/MY_ACCOUNT_ID

Trait Implementations

impl Debug for Destination

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.