In the context of messaging systems, messages and events are related but not necessarily the same.
They represent different types of data that can be exchanged between components or services within a distributed system. The distinction between the two are:
- Refer to discrete units of data.
- Often structured and can carry information such as commands, requests, responses, or data payloads.
- Usually directed at specific recipients, and are often used for point-to-point communication.
- Are notifications or occurrences that represent something of interest within a system (e.g: something happened).
- Typically broadcast to multiple subscribers (listeners or consumers).
- Often unstructured and may not carry detailed data payloads. They are more about signaling that an important incident or state change has happened.
- Commonly used for publish-subscribe (pub/sub) or event-driven architectures.
They both serve as a means of communication within distributed systems. Messages are generally used for directed communication with specific content, while events are used for broadcasting notifications about something noteworthy happening within the system, often to multiple interested parties.
In a lot of cases, the two terms are used interchangeably, as the frontier between the two is not clearly defined, or is not considered important.