Event Queue Endpoint

Tempo MQTT Integration — Outbound Publishing

Overview

Tempo can publish platform events to an external MQTT broker that you (the partner) operate. Tempo acts purely as an MQTT client — it connects, publishes, and disconnects. You provide the broker, credentials, and subscribe to the topics you care about.

MQTT is one of three outbound transports Tempo supports (MQTT, RabbitMQ, REST); this document covers MQTT only.

Connection & Authentication

Aspect	Value
Role	Tempo is the publishing client; you host the broker
URL schemes	`mqtt`, `mqtts`, `tcp`, `tls`, `ws`, `wss`
TLS	Use `mqtts://host:8883` for TLS; `mqtt://host:1883` for plaintext
Authentication	Basic — username + password in the MQTT CONNECT packet
Connect timeout	10 seconds
Publish QoS	2 (exactly-once)
Connection model	Connect → publish one message → disconnect, per event
Credentials	Configured per endpoint; stored encrypted on our side and never logged

Topics we publish to

Each event publishes to a topic derived from the event's type and trigger:

{event_type}/{event_trigger}

…with spaces replaced by underscores and the whole string lowercased. For standard events this topic is automatically derived and is not free-form configurable.

Concrete topics

Domain	Topic
Batch run status	`batch/batch_run_status`
Procedure run state	`procedure_run/procedure_run_state`
Procedure step execution	`procedure_run/step_execution`
Material inventory movement	`material_inventory/material_inventory_movement`
Custom event (deprecated)	`custom_event/custom_event`
Exception sync	`exception/exception_sync`
Printing — material sublot	`printing/printing_material_sublot`
Printing — dispense	`printing/printing_dispense`
Printing — material output (primary)	`printing/printing_material_output_primary`
Printing — material output (by-product)	`printing/printing_material_output_bi_product`
Printing — material output (intermediate)	`printing/printing_material_output_intermediate`
Printing — equipment	`printing/printing_equipment`
Printing — create kit	`printing/printing_create_kit`
Printing — sample	`printing/printing_sample`
Printing — load array	`printing/printing_load_array`
Printing — create label	`printing/printing_create_label`

Which of these are active depends on the event configurations enabled for your integration — you only receive events for triggers that have been configured to publish to your endpoint.

Payload

The message body is the event's JSON object (UTF-8), specific to the event type (e.g. a batch-run-status object, an inventory-movement object). Only printing event types can have their payload modified.

Metadata is attached only when the event configuration has metadata-in-payload enabled. When enabled, it is merged into the message under a top-level Metadata key:

{
  "...event-specific fields...": "...",
  "Metadata": {
    "OrganizationID": "…",
    "OrganizationName": "…",
    "OrganizationURL": "…",
    "EventType": "Batch",
    "EventTrigger": "batch_run_status",
    "Subscriber": "<your endpoint name>",
    "CreatedBy": "<user email or 'System Auto Execution'>",
    "SourceEnvironment": "<environment>",
    "CreationDateTime": "2026-06-18T00:00:00.000Z"
  }
}

When metadata-in-payload is not enabled, the body is just the raw event object with no Metadata wrapper.

What you need to provide

Broker URL + port and scheme (TLS preferred: mqtts://…:8883)
MQTT username + password (basic auth)
Subscriptions on your broker for the topics above that correspond to the events you want
Confirmation of whether you want the Metadata block included in payloads

Caveats

Auth is basic only (username/password); no client-certificate / mutual-TLS auth in the current implementation.
Topics for standard events are fixed/auto-derived, not free-form.
Tempo publishes at QoS 2; broker durability, retained messages, and persistent sessions are the broker's (your) responsibility.
No ordering guarantee is provided across distinct events.