CQRS Manager for Distributed Reactive Systems (herein abbreviated CMDR) is one component in a distributed architecture that coordinates via a log (currenly Kafka). There are two primary topics for users of CMDR to be concerned with.
The name of the commands topic is configured in the CMDR processes as
COMMANDS_TOPIC.
Only CMDR shall write to the commands topic.
Only one command processor should handle each command type. The command processor is responsible to receive each command, determine whether the command is semantically valid (CMDR will only write syntactically valid commands to this topic), optionally write out to a data store, and then emit one or more events to the events topic.
TODO: schema management
A Command is provided to the CMDR HTTP API as a map in the following form (in a variety of acceptable media types, but the semantics are the same):
{:action :create-foo
:data {:a "map data payload"}}CMDR adds a UUID id field, so that when the command processor
receives it, its Kafka key is the UUID, and the Kafka value is a
Fressian map (serialization
format subject to change in future) in the following format:
{:id #uuid "ab675ea0-7f6d-11e6-bcdd-540e9df06c05"
:action :create-foo
:data {:a "map data payload"}}TODO: completing commands, and ?sync=true
The name of the commands topic is configured in the CMDR processes as
EVENTS_TOPIC.
CMDR doesn't write to the events topic, only application processes do.
When an command or event processor emits, or when an event processor receives, an event, it has a UUID Kafka key, and the Kafka value is a Fressian map (serialization format subject to change in future) in the following format:
{:id #uuid "075415a0-7f6e-11e6-bcdd-540e9df06c05"
:parent #uuid "ab675ea0-7f6d-11e6-bcdd-540e9df06c05"
:action :foo-created
:data {:a "map data payload"
:likely "with more keys generated upstream"}}TODO