Enum svc_agent::Source

pub enum Source<'a> {
    Broadcast(&'a AccountId, &'a str, &'a str),
    Multicast(Option<&'a AgentId>, Option<&'a str>),
    Unicast(Option<&'a AccountId>),
}

Message source.

This is an abstraction over MQTT topic pattern to determine the subscription topic to receive messages.

If you want to subscribe to a topic consider using Subscription builder or building RequestSubscription, ResponseSubscription or EventSubscription directly when you need something special.

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

MQTT topic variables:

• MY_ACCOUNT_ID – AccountId of the current agent that send the message.
• MY_VER – API version string of the current agent. For example: v1.
• ACCOUNT_ID – source AccountId (no specific agent).
• AGENT_ID – source AgentId.
• VER – source agent version.
• BROADCAST_URI source agent’s API specific path to some resource divided by /. For example: /rooms/ROOM_ID/events. Use + as single-level wildcard like /room/+/events to subscribe to events in all rooms and # as multi-level wildcard like /rooms/# to subscribe to all rooms and their nested resources.

Variants

Broadcast(&'a AccountId, &'a str, &'a str)

Receive a message along with other subscribers.

Typically used for receiving notification events from a service.

Value supplied are ACCOUNT_ID, VER and BROADCAST_URI.

Patterns

Type	Pattern	MQTT topic
event	any-from-app	apps/ACCOUNT_ID/api/VER/BROADCAST_URI

Tuple Fields of Broadcast

0: &'a AccountId1: &'a str2: &'a str

Multicast(Option<&'a AgentId>, Option<&'a str>)

Receive a message from any single of SharedGroup agents.

Typically used for receiving requests by services which may have multiple instances.

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

Optional values supplied are AGENT_ID and VER. If None is specified for either of the two then wildcard is being used to receive messages from any agent or its API version.

Patterns

Type	Pattern	MQTT topic
request	app-from-any	agents/+/api/+/out/MY_ACCOUNT_ID
request	app-from-any	agents/+/api/VER/out/MY_ACCOUNT_ID
request	app-from-any	agents/AGENT_ID/api/+/out/MY_ACCOUNT_ID
request	app-from-any	agents/AGENT_ID/api/VER/out/MY_ACCOUNT_ID

Tuple Fields of Multicast

0: Option<&'a AgentId>1: Option<&'a str>

Unicast(Option<&'a AccountId>)

Receive a message sent specifically to the current agent by its AGENT_ID.

Typically being used for receiving responses for requests. Also used for receiving a request by a specific instance of a stateful service.

Optional ACCOUNT_ID may be supplied to specify an AccountId to subscribe to. If None is specified then wildcard is being used to receive unicast messages from any account.

Patterns

Type	Pattern	MQTT topic
request	one-from-one	agents/MY_AGENT_ID/api/MY_VER/in/ACCOUNT_ID
request	one-from-any	agents/MY_AGENT_ID/api/MY_VER/in/+
response	one-from-one	agents/MY_AGENT_ID/api/MY_VER/in/ACCOUNT_ID
response	one-from-any	agents/MY_AGENT_ID/api/MY_VER/in/+

Tuple Fields of Unicast

0: Option<&'a AccountId>

Trait Implementations

impl<'a> Debug for Source<'a>

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

Formats the value using the given formatter.