Akka Serverless components include stateful Entities and stateless Actions. You define the service interface and—for Entities—the domain data model, in
.proto files as gRPC descriptors. Separating the service interface and data model in different files allows you to evolve them independently.
The gRPC definitions describe the external interface, messages, and events. From the
.proto files, the gRPC CLI,
protoc, generates the code framework for remote procedure calls, data access, and serialization.
Stateful services can implement Value Entity or Event Sourced Entity components and stateless services implement Actions. Typically, a stateful service should only have one Entity type, but can also include Actions.
Actions are stateless functions that can be triggered by gRPC or HTTP calls. They can also subscribe to published events, and they can send commands to other services based on the events they receive.
For stateful services, you implement Value Entities or Event Sourced Entities that contain your business logic. At runtime, command messages will invoke operations on Entities. A command may only act on one Entity at a time. If you would like to update multiple Entities from a single command, you can use forwarding and effects.
Services can interact asynchronously with other services and with external systems. Event Sourced Entities emit events to a journal, to which other services can subscribe. By configuring your own publish/subscribe (pub/sub) mechanism, any service can publish their own events and subscribe to events published by other services or external systems.
Find more details and examples for developing:
You can test and debug your services by running them locally before deploying to Akka Serverless.