The envelope adds a series of message headers, including: MassTransit encapsulates every sent or published message in a message envelope (described by the Envelope Wrapper pattern). OrderSubmitted, OrderAccepted, OrderRejected, OrderShipped.Events are published (using Publish) via either ConsumeContext (within a message consumer), IPublishEndpoint (within a container scope), or IBus (standalone).Įvents should be expressed in a noun-verb (past tense) sequence, indicating that something happened. For example:Īn event signifies that something has happened. For low- to medium-volume message loads this isn't a major concern, but for larger high-volume loads it may be preferable to send (using Send) commands directly to the queue to reduce latency and cost.Ĭommands should be expressed in a verb-noun sequence, following the tell style. However, both Azure Service Bus and Amazon SQS have a more complicated routing structure and because of that structure, additional charges may be incurred since messages need to be forwarded from topics to queues. When using RabbitMQ, there is no additional overhead using this approach. By maintaining the one-to-one relationship of a command to a consumer, commands may by published and they will be automatically routed to the consumer. If you have a command, such as SubmitOrder, then you should have only one consumer that implements IConsumer or one saga state machine with the Event configured.
CommandsĪ command tells a service to do something, and typically a command should only be consumed by a single consumer. When choosing a name for a message, the type of message should dictate the tense of the message. There are two main message types, events and commands. Don't create an exchange or topic unless it is directly consumed or publishedĭon't create a middleware filter for the message type
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