HTTP Event Storage Adapter

DRY Castore EventStorageAdapter implementation using a HTTP API.

This class is mainly useful when you already have the logic for events implemented and you want to expose your methods for a front-end to use them, eg.

📥 Installation

# npm
npm install @castore/event-storage-adapter-http

# yarn
yarn add @castore/event-storage-adapter-http

This package has @castore/core as peer dependency, so you will have to install it as well:

# npm
npm install @castore/core

# yarn
yarn add @castore/core

👩‍💻 Usage

import { HttpEventStorageAdapter } from '@castore/event-storage-adapter-http';
import { swagger } from './swagger.json'; // your swagger file


const pokemonHttpEventStorageAdapter = new HttpEventStorageAdapter({ swagger });

const pokemonEventStore = new EventStore({
  ...
  eventStorageAdapter: pokemonHttpEventStorageAdapter,
});

🤔 How it works

You need to expose 2 API endpoints that will be used by the adapter. They need to return the data correctly formatted:

• getEvents: (aggregateId: string) => { events: EventDetail[] }
• listAggregateIds: () => ListAggregateIdsOutput

See here for more details about the EventDetails type. For the ListAggregateIdsOutput type:

type ListAggregateIdsOutput = {
  aggregateIds: {
    aggregateId: string;
    initialEventTimestamp: string;
  }[];
  nextPageToken?: string;
};

Once your API is deployed, you can export is as an OpenAPI specification (swagger) and pass it to the adapter. Here is how export an API gateway as a swagger.

This adapter uses the swagger passed in input to generate requests to you API endpoints. For each method, it looks for the tags operationId in the swagger to generate the request.

The swagger should be typed like this, with at least the paths for the getEvents and listAggregateIds methods:

type Swagger = {
  openapi: string; // the OpenAPI version you are using. Ex: 3.0.1
  info: {
    title: string; // the title of your API
    version: string; // timestamps
  };
  servers: {
    url: string; // the base url of your API
    variables: {
      basePath: {
        default: string; // the default value can be ''
      };
    };
  }[];
  paths: {
    [path: string]: {
      [verb: string]: {
        operationId: string; // the operation id for the castore method (getEvents | listAggregateIds)
        responses: {
          [statusCode: string]: {
            description: string;
            content?: {
              [type: string]: {
                schema: {
                  $ref: string;
                };
              };
            };
          };
          default: {
            description: string;
          };
        };
        parameters?: {
          name: string;
          in: string; // 'path' | 'query' | 'header' | 'cookie'
          description: string;
          required: boolean;
          format: string;
        }[];
      };
    };
  };
};

📝 Examples

Example of swagger:

{
  "openapi": "3.0.1",
  "info": {
    "title": "event-store-api",
    "version": "2023-10-27 14:58:17UTC"
  },
  "servers": [
    {
      "url": "https://yourApiGatewayId.execute-api.eu-west-1.amazonaws.com/{basePath}",
      "variables": {
        "basePath": {
          "default": ""
        }
      }
    }
  ],
  "paths": {
    "/aggregateIds": {
      "get": {
        "responses": {
          "default": {
            "description": "Default response for GET /aggregateIds"
          }
        },
        "operationId": "listAggregateIds"
      }
    },
    "/events?aggregateId={aggregateId}": {
      "get": {
        "responses": {
          "default": {
            "description": "Default response for GET /events"
          }
        },
        "x-castore-operationId": "getEvents",
        // you can alternatively use the operationId field
        // "operationId": "getEvents",
        "parameters": [
          {
            "name": "aggregateId",
            "in": "path",
            "description": "aggregateId of the event-trace we want to retrieve",
            "required": true,
            "format": "int64"
          }
        ]
      }
    }
  }
}

Note that if you don't specify the x-castore-operationId or the operationId field, then the adapter will not be able to find the method to call.