# MqttBridge API

EventBridge implementation for MQTT 5 brokers.

---
Canonical: /handbook/api/classes/_purista_mqttbridge.MqttBridge/
Source: mqttbridge/src/MqttEventBridge.ts
Format: Markdown for agents
---

EventBridge implementation for MQTT 5 brokers.

Package: `@purista/mqttbridge`

## Signature

```typescript
class MqttBridge
```

## Examples

```typescript
import { MqttBridge } from '@purista/mqttbridge'

// create and init our eventbridge
const eventBridge = new MqttBridge()
await eventBridge.start()
```

## Members

### Constructors

- `new constructor(config?: { allowRetries: boolean; defaultCommandTimeout: number; defaultMessageExpiryInterval: number; defaultSessionExpiryInterval: number; emptyTopicPartString: string; instanceId: string; ... })` — Creates an MQTT bridge with defaults merged into MQTT client options.

### Properties

- `capabilities: EventBridgeCapabilities` — Runtime capability matrix used for strict startup validation.
- `client: MqttClient | undefined` — MQTT client instance, available after start.
- `config: Complete<EventBridgeConfig<ConfigType>>`
- `defaultCommandTimeout: number` — The default time until when a command invocation automatically returns a time out error
- `inFlightExecutions: InFlightExecutionTracker`
- `instanceId: string` — Stable runtime instance id used to distinguish bridge processes.
- `logger: Logger`
- `metricsRecorder: PuristaMetricsRecorder`
- `name: string` — Human-readable bridge name used in logs, traces, and metrics.
- `pendingInvocations: PendingInvocationRegistry<unknown>` — Pending command invocations waiting for MQTT correlation responses.
- `traceProvider: NodeTracerProvider`

### Methods

- `destroy(): Promise<void>` — Rejects pending invocations, waits for in-flight handlers, and closes the
MQTT client.
- `emitMessage<T>(message: Omit<EBMessage, "id" | "timestamp" | "correlationId">, contentType: string, contentEncoding: string): Promise<Readonly<EBMessage>>` — Publishes a PURISTA event/message as a JSON MQTT payload.
- `getInFlightExecutionCount(): number` — Number of currently running handlers across all work kinds.
- `getInFlightExecutionCounts(): InFlightExecutionCounts` — Number of currently running handlers grouped by work kind.
- `getPausedSubscriptionConsumers(): PausedSubscriptionConsumersByRegistrationKey` — Returns paused subscription consumer states keyed by adapter registration key.
- `getTracer(): Tracer` — Returns open telemetry tracer of this service
- `invoke<T>(input: Omit<Command, "id" | "messageType" | "timestamp" | "correlationId">, commandTimeout: number): Promise<T>` — Invokes a command over MQTT and waits for a correlated response message.
- `isHealthy(): Promise<boolean>` — Indicates whether the MQTT client is connected.
- `isReady(): Promise<boolean>` — Indicates whether the MQTT client is connected.
- `openStream<Chunk, Final>(_input: Omit<StreamOpenRequest, "id" | "messageType" | "timestamp" | "correlationId">, _ttl?: number): Promise<StreamHandle<Chunk, Final>>` — Open a stream invocation.
- `registerCommand(address: EBMessageAddress, cb: (message: { contentEncoding: string; contentType: string; correlationId: string; eventName: string; id: string; messageType: Command; ... }) => Promise<{ contentEncoding: "utf-8"; contentType: "application/json"; correlationId: string; eventName: string; id: string; isHandledError: boolean; ... } | { contentEncoding: string; contentType: string; correlationId: string; eventName: string; id: string; messageType: CommandSuccessResponse; ... }>, metadata: CommandDefinitionMetadataBase, eventBridgeConfig: DefinitionEventBridgeConfig): Promise<string>` — Registers a command handler on the shared MQTT command topic.
- `registerStream(_address: EBMessageAddress, _cb: (message: StreamMessage) => Promise<void>, _metadata: StreamDefinitionMetadataBase, _eventBridgeConfig: DefinitionEventBridgeConfig): Promise<string>` — Register a service stream handler for a service target.
- `registerSubscription(subscription: Subscription, cb: (message: EBMessage) => Promise<Omit<{ contentEncoding: unknown; contentType: unknown; correlationId: unknown; eventName: unknown; id: unknown; messageType: unknown; ... }, unknown | unknown> | undefined>): Promise<string>` — Registers a subscription handler on a topic derived from the subscription
filter.
- `resumeSubscriptionConsumer(_registrationKey: string): Promise<void>` — Resumes a paused subscription consumer by registration key.
- `runInFlight<T>(fn: () => Promise<T>, kind?: "command" | "subscription" | "stream" | "generic"): Promise<T>`
- `start(): Promise<void>` — Connects to the MQTT broker and subscribes to this instance's command
response topic.
- `startActiveSpan<F>(name: string, opts: SpanOptions, context: Context | undefined, fn: (span: Span) => Promise<F>): Promise<F>` — Start a child span for opentelemetry tracking
- `unregisterCommand(address: EBMessageAddress): Promise<void>` — Unsubscribes a command handler topic and removes it from the local router.
- `unregisterStream(_address: EBMessageAddress): Promise<void>` — Unregister a service stream
- `unregisterSubscription(address: EBMessageAddress): Promise<void>` — Unsubscribes and removes a registered subscription handler.
- `waitForInFlightDrain(timeoutMs?: number): Promise<boolean>`
- `wrapInSpan<F>(name: string, opts: SpanOptions, fn: (span: Span) => Promise<F>, context?: Context): Promise<F>` — Start span for opentelemetry tracking on same level.
The created span will not become the "active" span within opentelemetry!