The communication.xml file is used to define message queue topics and link publishers with subscribers. This is required when setting up asynchronous handling for events such as order processing.
B (queue_topology.xml): Defines queue and exchange structure.
C (queue_consumer.xml): Defines consumers for queues but does not declare topics.
A is correct: communication.xml is the right file for defining topics.
Reference:
Adobe Commerce DevDocs - communication.xml reference
In Adobe Commerce's Message Queue Framework (MQF), several XML configuration files are used, each with a specific purpose:
communication.xml # Defines message queue topics and the messages they carry.
Topics represent logical channels that connect publishers and consumers.
Example: An order placement event may publish a message to a topic like order.processing.
queue_topology.xml # Defines the relationship between topics and queues.
Maps a topic to one or more queues.
Specifies routing and exchange bindings.
queue_consumer.xml # Defines consumers that process messages from queues.
Each consumer is a PHP class responsible for handling a message pulled from a queue.
Since the question specifically asks about setting up a topic (not the routing or consumer), the correct configuration file is communication.xml.
Official Documentation Extracts:
"The communication.xml file defines the messages and topics in the message queue framework."- Adobe Commerce DevDocs: Message queues configuration
"Use queue_topology.xml to bind topics to queues and define exchanges."- Message Queues: Topology configuration
"Consumers are defined in queue_consumer.xml. A consumer listens to a queue and processes incoming messages."- Message Queues: Consumer configuration