simerplaha/akka-typed-eventsourcing

An implementation of Eventsourcing with Akka-typed, Spray, Slick & Postgres.

Akka-typed-eventsourcing

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An implementation of Eventsourcing with Akka-typed, Spray, Slick & Postgres.

Summary

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1. A simple Spray REST API to submit commands to Akka-typed's ActorSystem.
2. Implements "Actor per request" pattern using typed actors.
3. Provides base implementations for AggregateManager and Aggregate.
4. Uses Akka-typed's Total behavior's lifecycle event 'PreStart' to replay all stored events which restores Actor's state.
5. Implements an example of CQRS's read side using Akka's EventBus (Check UserListener).
6. Maps stored JSON events to relevant Case classes.
7. Uses Slick-pg extension.
8. Uses Gson for JSON parsing.

Running

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1. Add your postgres database configuration in application.conf
2. Run Schema.scala's main method to create the database schema
3. Run Boot.scala to start application.

EVENTS table

PERSISTENT_ID	EVENT_JSON	EVENT_NAME	TAGS	CREATE_TIME
String	String	String	List[String]	Timestamp

APIs

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Command: CreateUser

Event - UserCreated

http://localhost:8080/createUser?username=John&name=Smith&password=123

{
    "username": "John",
    "name": "Smith",
    "password": "123",
    "deleted": false
}

Running the same URL again returns error message

{
    "message": "Username 'John' with name 'Smith' already exists."
}

Command: UpdateName

Event - UserNameUpdated

http://localhost:8080/updateName?username=John&name=Jhonny

{
    "username": "John",
    "name": "Jhonny",
    "password": "123",
    "deleted": false
}

Running the same URL again returns error message

{
    "message": "Name unchanged!",
    "state": {
        "username": "John",
        "name": "Jhonny",
        "password": "123",
        "deleted": false
    }
}

Command: ChangePassword

Event - UserPasswordChanged

http://localhost:8080/changePassword?username=John&password=PA$$W0RD

{
    "username": "John",
    "name": "Jhonny",
    "password": "PA$$W0RD",
    "deleted": false
}

Command: DeleteUser

Event - UserDeleted

http://localhost:8080/deleteUser?username=John

{
    "username": "John",
    "name": "Jhonny",
    "password": "PA$$W0RD",
    "deleted": true
}

Calling CreateUser on a delete users display this message: http://localhost:8080/createUser?username=John&name=Smith&password=123

{
    "message": "Not a valid request: 'Initialize' for current state: 'deleted'",
    "state": {
        "username": "John",
        "name": "Jhonny",
        "password": "PA$$W0RD",
        "deleted": true
    }
}

TODOs

• Test cases
• Stopping Actors after reaching certain threshold of in-memory Actors.
• Snapshotting
• Use Kafka as eventstore instead.