MqttActor

Defined in: src/io/broker/MqttActor.ts:78

Typed, subclass-first MQTT 3.1.1 / 5.0 actor backed by the mqtt peer-dep — the MQTT counterpart to WebsocketClientActor. Extend it, declare subscriptions in the constructor, and handle inbound traffic in onMessage:

class MyClient extends MqttActor {
  constructor(opts: MqttOptions) {
    super(opts.withQos(1).withClientId('my-client'));
    this.subscribe('some/thing/#');
  }
  override onMessage(msg: MqttMessage): void {
    this.log.info(msg.payload.text());
    this.publish(msg.topic, 'pong');
  }
}

T types the inbound payload (msg.payload.entity(): T); TSelf types application messages other actors may tell this ref (defaults to never). It is still externally controllable: ref.tell(cmd) with a MqttCommand publishes / subscribes / unsubscribes; a subscribe command with no target routes to this actor’s own onMessage, with a target fans out to that actor.

Lifecycle events (inbound / connected / disconnected) are delivered through the mailbox, so onMessage and the hooks always run on the actor thread (single-threaded, per-connection order preserved).

Extends

• BrokerActor<MqttOptionsType, MqttActorMessage<T, TSelf>, MqttPublish>

Type Parameters

T

T = unknown

TSelf

TSelf = never

Constructors

Constructor

new MqttActor<T, TSelf>(options?): MqttActor<T, TSelf>

Defined in: src/io/broker/MqttActor.ts:93

Parameters

options?

MqttOptions = {}

Returns

MqttActor<T, TSelf>

Overrides

BrokerActor<MqttOptionsType, MqttActorMessage<T, TSelf>, MqttPublish>.constructor

Methods

displayName()

displayName(): string

Defined in: src/Actor.ts:192

Human-readable name for this actor in log lines and in the DevTools actor tree (#891). Defaults to the full path — which is already the log source, so an actor that doesn’t override this logs exactly as it did before.

override displayName(): string { return `User(${this.entityId})`; }

Purely cosmetic. The path stays the identity everywhere that routes, correlates or aggregates — metric labels, tracing attributes, dead letters, ActorRef.toString(), every wire identifier — so a display name is free to be ambiguous, unstable, or shared between actors.

Resolved on every record, not captured once. Two consequences: keep it cheap and side-effect free, and expect it to be called before preStart (hence the optional chain — the context is attached after construction). In exchange a name may be derived from state, and it updates when that state does. Throwing, or returning anything but a non-empty string, falls back to the path and warns once: a naming hook must not be able to take a log line down with it.

ActorOptions.withDisplayName(...) outranks this, for the same reason withSupervisorStrategy(...) outranks supervisorStrategy — the spawn site is the more specific statement. It has to: every Behaviors actor is a TypedActor that inherits this default, so a method that won would silently swallow the spawn-site value for exactly the actors that have no subclass to override. For a name that only becomes known at runtime, this.context.setDisplayName(...) outranks both.

Returns

string

Inherited from

BrokerActor.displayName

---

onMessage()

abstract onMessage(message): void | Promise<void>

Defined in: src/io/broker/MqttActor.ts:100

Handle one inbound message on this actor’s own subscriptions.

Parameters

message

MqttMessage<T>

Returns

void | Promise<void>

---

postRestart()

postRestart(_reason): void | Promise<void>

Defined in: src/Actor.ts:152

Called on the fresh instance after a restart. Default: call preStart().

Parameters

_reason

Error

Returns

void | Promise<void>

Inherited from

BrokerActor.postRestart

---

postStop()

postStop(): Promise<void>

Defined in: src/io/broker/BrokerActor.ts:486

Called after the actor has been terminated. Children are already stopped.

Returns

Promise<void>

Inherited from

BrokerActor.postStop

---

preRestart()

preRestart(_reason, _message?): void | Promise<void>

Defined in: src/Actor.ts:119

Called before a restart, on the instance about to be thrown away. The default calls postStop() and nothing else.

Override to release what the instance holds outside itself — a file handle, an open socket, a broker connection — or to do something other than drop the message that failed.

Stopping this actor’s children is not done here: the framework tears them down after this hook returns and waits for them before building the replacement, because postRestart re-runs preStart and a named child needs its name back. To keep the children instead, see Actor.stopChildrenOnRestart.

Parameters

_reason

Error

_message?

MqttActorMessage<T, TSelf>

Returns

void | Promise<void>

Inherited from

BrokerActor.preRestart

---

preStart()

preStart(): Promise<void>

Defined in: src/io/broker/MqttActor.ts:377

Called after construction and before the first message is processed.

Returns

Promise<void>

Overrides

BrokerActor.preStart

---

stopChildrenOnRestart()

stopChildrenOnRestart(): boolean

Defined in: src/Actor.ts:149

Whether a restart tears this actor’s children down before rebuilding it. Default: true.

A restart replaces the Actor instance while the cell — and therefore the child map — survives. Keeping the children was the old behaviour and it made an ordinary pattern impossible: postRestart re-runs preStart, so an actor that spawns a named child there hit Child name … is not unique on its first restart and never recovered (#634).

Override to false when the children are expensive to rebuild, hold state the parent cannot restore, or are supervised independently — a connection pool, say. They then outlive the restart exactly as before, and it is on you to make preStart idempotent — by adopting the survivor from the cell, this.child = this.context.child('name').toNullable() ?? this.context.spawn(Child, 'name'), or with context.spawnAnonymous. An instance field cannot do it: preStart runs on a fresh instance after every restart, so this.child ??= … is always unset and re-spawns into the name the surviving child still holds, which fails the spawn and restarts the actor again.

This is a separate hook rather than a preRestart override because the teardown has to be awaited: the new instance cannot be built until the old children are actually gone, and preRestart has no way to tell the cell that it started something worth waiting for.

Returns

boolean

Inherited from

BrokerActor.stopChildrenOnRestart

---

supervisorStrategy()

supervisorStrategy(): SupervisorStrategy

Defined in: src/Actor.ts:160

Supervisor strategy for this actor’s children. Defaults to restart, up to 10 times per minute, then stop.

Returns

SupervisorStrategy

Inherited from

BrokerActor.supervisorStrategy