npm package: @marek.libra/plugin-notifications-backend
Description: This Backstage backend plugin provides REST API endpoint for the notifications.
Latest version: 1.2.1-1

# Notifications

This Backstage backend plugin provides REST API endpoint for the notifications.

It's backed by a relational database, so far tested with PostgreSQL.

## Deploying as a dynamic plugin

The notifications backend plugin can be loaded either as a static or a dynamic plugin.

To install it as a dynamic plugin, please follow instructions here: https://github.com/janus-idp/backstage-showcase/blob/main/showcase-docs/dynamic-plugins.md#installing-a-dynamic-plugin-package-in-the-showcase

To install it as a static plugin, several steps are required as described below for both the legacy backend and the new backend system.

In any case, do not miss the info about configuration and especially about creating entities [in the Catalog as described below](#important-user-entities-in-catalog).

## Getting started

The plugin uses a relational database to persist messages, it has been tested with the SQLite and PostgreSQL.

Upon the backend's plugin start, the `backstage_plugin_notifications` database and its tables are created automatically.

### Optional: PostgreSQL setup

**To use the Backstage's default SQLite database, no specific configuration is needed.**

The following steps describe requirements for PostgreSQL:

- Install [PostgresSQL DB](https://www.postgresql.org/download/)
- Configure Postgres for tcp/ip
  Open Postgres conf file for editing:

```bash
sudo vi /var/lib/pgsql/data/pg_hba.conf
```

Add this line:

```bash
host   all             postgres       127.0.0.1/32                          password
```

- Start Postgres server:

```bash
sudo systemctl enable --now postgresql.service
```

#### Backstage configuration for PostgreSQL

If PostgreSQL is used, additional configuration in the `app-config.yaml` file or `app-config.local.yaml` file is needed. Example:

```yaml
backend:
  database:
    client: pg
    connection:
      host: 127.0.0.1
      port: 5432
      user: postgres
      password: your_secret
    knexConfig:
      pool:
        min: 3
        max: 12
        acquireTimeoutMillis: 60000
        idleTimeoutMillis: 60000
  cache:
    store: memory
```

## Deploy as a static plugin

### Add NPM dependency

```bash
cd packages/backend
yarn add @janus-idp/plugin-notifications-backend
```

### Add the backend-plugin for the legacy backend

Create a `packages/backend/src/plugins/notifications.ts` file with the following content:

```ts title="packages/backend/src/plugins/notifications.ts"
import { CatalogClient } from '@backstage/catalog-client';

import { Router } from 'express';

import { createRouter } from '@janus-idp/plugin-notifications-backend';

import { PluginEnvironment } from '../types';

export default async function createPlugin(
  env: PluginEnvironment,
): Promise<Router> {
  return await createRouter({
    identity: env.identity,
    logger: env.logger,
    permissions: env.permissions,
    tokenManager: env.tokenManager,
    database: env.database,
    discovery: env.discovery,
    config: env.config,
  });
}
```

In the `packages/backend/src/index.ts`, add the following:

```ts title="packages/backend/src/index.ts"
import notifications from './plugins/notifications';
...
// Existing code for reference:
const apiRouter = Router();
...
// New code:
const notificationsEnv = useHotMemoize(module, () =>
  createEnv('notifications'),
);
apiRouter.use('/notifications', await notifications(notificationsEnv));
```

### Installing the plugin for the new backend system

Add the following code to the `packages/backend/src/index.ts`:

```ts title="packages/backend/src/index.ts"
const backend = createBackend();

/* highlight-add-next-line */
backend.add(import('@janus-idp/backstage-plugin-notifications-backend/alpha'));

backend.start();
```

## Configuration

### Optional: Plugin configuration

If you have issues to create valid JWT tokens by an external caller, use following option to bypass the service-to-service configuration for them:

```yaml
notifications:
  # Workaround for issues with external caller JWT token creation.
  # When following config option is not provided and the request "authentication" header is missing, the request is ALLOWED by default
  # When following option is present, the request must contain either a valid JWT token or that provided shared secret in the "notifications-secret" header
  externalCallerSecret: your-secret-token-shared-with-external-services
```

We suggest using HTTPS to help prevent leaking the shared secret.

Example Request:

```bash
curl -X POST http://localhost:7007/api/notifications/notifications -H "Content-Type: application/json" -H "notifications-secret: your-secret-token-shared-with-external-services" -d '{"title":"my-title","origin":"my-origin","message":"message one","topic":"my-topic"}'

```

Notes:

- The `externalCallerSecret` is an workaround, exclusive use of JWT tokens will probably be required in the future.
- Sharing the same shared secret with the "auth.secret" option is not recommended.

## Authentication

Please refer to https://backstage.io/docs/auth/ to set-up authentication.

The Notifications flows are based on the identity of the user.

All `targetUsers`, `targetGroups`` or signed-in users receiving notifications must have corresponding entities created in the Catalog.
Refer to https://backstage.io/docs/auth/identity-resolver for details.

For the purpose of development, there is a `users.yaml` file listing example data to create a Guest user entity.

## Authorization

Every service endpoint is guarded by a permission check, enabled by default.

It is up to particular deployment to provide corresponding permission policies based on https://backstage.io/docs/permissions/writing-a-policy. To register your permission policies, refer to https://backstage.io/docs/permissions/getting-started#integrating-the-permission-framework-with-your-backstage-instance.

### Service-to-service and External Calls

The notifications-backend is expected to be called by frontend plugins (including the Notifications frontend plugin), other backend plugins or external services.

To configure those two flows, refer to:

- https://backstage.io/docs/auth/service-to-service-auth.
- https://backstage.io/docs/auth/service-to-service-auth#usage-in-external-callers

### Important: User entities in Catalog

_The notifications require target users or groups (as receivers) to be listed in the Catalog._

As an example how to do it, add following to the config:

```yaml
catalog:
  import:
    entityFilename: catalog-info.yaml
    pullRequestBranchName: backstage-integration
  rules:
    # *** Here is a new change:
    - allow: [Component, System, API, Resource, Location, User, Group]
  locations:
    # Local example data, file locations are relative to the backend process, typically `packages/backend`
    - type: file
      # *** Here is a new change, refers to a file stored in the root of the Backstage:
      target: ../../users.yaml
```

The example list of users is stored in the `plugins/notifications-backend/users.yaml` and can be copied to the root of the Backstage for development purposes.

## REST API

See `src/openapi.yaml` for full OpenAPI spec.

### Posting a notification

A notification without target users or groups is considered a system notification. That means it is intended for all users (listed among Updates in the UI).

Request (User message and then system message):

```bash
curl -X POST http://localhost:7007/api/notifications/notifications -H "Content-Type: application/json" -d '{"title": "My message title", "message": "I have nothing to say", "origin": "my-origin", "topic":"my topic", "targetUsers": ["default/guest"], "actions": [{"title": "my-title", "url": "http://foo.bar"}, {"title": "another action", "url": "https://foo.foo.bar"}]}'
```

Optionally add `-H "Authorization: Bearer eyJh.....` with a valid JWT token if the service-to-service authorization is enabled (see above).

Response:

```json
{ "msgid": "2daac6ff-3aaa-420d-b755-d94e54248310" }
```

### Get notifications

Page number starts at '1'. Page number '0' along with page size '0' means no paging.
User parameter is mandatory because it is needed for message status and filtering (read/unread).

Query parameters:

- `pageSize`. 0 means no paging.
- `pageNumber`. first page is 1. 0 means no paging.
- `orderBy`.
- `orderByDirec`. asc/desc
- `containsText`. filter title and message containing this text (case insensitive)
- `createdAfter`. fetch notifications created after this point in time
- `messageScope`. all/user/system. fetch notifications intended for specific user or system notifications or both
- `read`. true/false (read/unread)

Request:

```bash
curl 'http://localhost:7007/api/notifications/notifications?read=false&pageNumber=0&pageSize=0'
```

Response:

```json
[
  {
    "id": "2daac6ff-3aaa-420d-b755-d94e54248310",
    "created": "2023-10-30T13:48:34.931Z",
    "isSystem": false,
    "readByUser": false,
    "origin": "my-origin",
    "title": "My title",
    "message": "I have nothing to tell",
    "topic": "my-topic",
    "actions": []
  }
]
```

### Get count of notifications

User parameter is mandatory because it is needed for filtering (read/unread).

**Important: Logged-in user:**

The query requires a signed-in user whose entity is listed in the Catalog.
With this condition is met, the HTTP `Authorization` header contains a JWT token with the user's identity.

Optionally add `-H "Authorization: Bearer eyJh.....` with a valid JWT token to the `curl` commands bellow.

Query parameters:

- `containsText`. filter title and message containing this text (case insensitive)
- `createdAfter`. fetch notifications created after this point in time
- `messageScope`. all/user/system. fetch notifications intended for specific user or system notifications or both
- `read`. true/false (read/unread)

Request:

```bash
curl http://localhost:7007/api/notifications/notifications/count
```

Response:

```json
{ "count": "1" }
```

### Set notification as read/unread

Request:

```bash
curl -X PUT 'http://localhost:7007/api/notifications/notifications/read?messageID=48bbf896-4b7c-4b68-a446-246b6a801000&read=true'
```

Response: A HTTP Status Code

## Building a client for the API

We supply an Open API spec YAML file at `src/openapi.yaml`.