EventStoreDB

Run the db

$ docker-compose up

Admin UI

Hotswap code changes

$ cd EventSourcing
$ dotnet watch run

API

Commands

Create a new todo list

$ curl --request POST \
  --url https://localhost:5001/api/todolist \
  --header 'Content-Type: application/json' \
  --data '{
	"id": "cc3e7c41-9c82-4747-ab6d-8c284447e99a"
}'

// response
{
  "id": "19c3bcfa-58f8-4d4c-8c7c-495be0e2946c",
  "revision": 0,
  "response": null
}

Add Item to TodoList

To add items to the list the most recent revision number needs to be included in the command, this ensures that the list has not been modified since the last read by this client. (Almost like optimistic locking)

$ curl --request POST \
  --url https://localhost:5001/api/TodoList/cc3e7c41-9c82-4747-ab6d-8c284447e99a/items \
  --header 'Content-Type: application/json' \
  --data '{
	"itemId": "9b709490-76e5-4949-b0ca-967a2064fc6e",
	"description": "task 1",
	"expectedRevision": 0
}'

// response

{
  "id": "9b709490-76e5-4949-b0ca-967a2064fc6e",
  "revision": 1,
  "response": null
}

Queries

Query models are built using 2 different mechanisms, subscriptions and projections. With subscriptions the application listens to events and the creates/updates the query model and stores it outside of eventStoreDb (e.g Relational DB or memory). Projections on the other hand are registered inside of eventStoreDb. The projections typically run continuously and are updated as new events are appended to target streams. The results of projections are stored in a stream on eventStoreDb. Projections execute on the eventStoreDb, not on the client.

List all todo lists (Using subscription query model)

$ curl --request GET \
  --url https://localhost:5001/api/todolist \
  --header 'Content-Type: application/json'
  
 // response 

[
  {
    "id": "88bce914-bfc0-499a-9f12-7beba879f25c",
    "numberOfTasks": 0,
    "revision": 0
  },
  {
    "id": "6ff10606-78df-4db2-b50e-11e4eb94cebd",
    "numberOfTasks": 3,
    "revision": 3
  },
  {
    "id": "f1f3ffa8-dac9-46fe-9f77-1eae45f9ece5",
    "numberOfTasks": 0,
    "revision": 0
  }
]

List all todo lists (Using projection query model)

$ curl --request GET \
  --url 'https://localhost:5001/api/todolist?using=projection' \
  --header 'Content-Type: application/json'

Get a specific TodoList (Using subscription query model)

$ curl --request GET \
  --url https://localhost:5001/api/todolist/6ff10606-78df-4db2-b50e-11e4eb94cebd \
  --header 'Content-Type: application/json'

// response

{
  "id": "6ff10606-78df-4db2-b50e-11e4eb94cebd",
  "tasks": [
    {
      "taskId": "fae0f902-fc43-4f17-aec1-8ddc03b8bc48",
      "description": "task 1"
    },
    {
      "taskId": "66f6f33d-ef82-4cec-9558-eec8fc40e11f",
      "description": "task 2"
    },
    {
      "taskId": "66e7e1ee-f84d-44b4-af18-99c89af38353",
      "description": "task 3"
    }
  ],
  "revision": 3
}

Get a specific TodoList (Using projection query model)

$ curl --request GET \
  --url 'https://localhost:5001/api/todolist/ee5fbd4e-e79a-42cb-a07a-12177da7d23a?using=projection' \
  --header 'Content-Type: application/json'

References

• https://github.com/evgeniy-khist/eventstoredb-event-sourcing