nodejs-event-driven
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NodeJS agnostic event driven with EventEmitter support
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[](https://www.npmjs.com/package/nodejs-event-driven)
[](https://codecov.io/gh/openhoat/nodejs-event-driven)
## NodeJS Event Driven
Purpose: provide an agnostic event driven solution inspired by the simplicity of EventEmitter interface.
Features:
- In memory queue
- File system queue
- Redis queue
- RabbitMQ
- Kafka
### How it works
Simply instantiate an `EventBusService` and use it as an `EventEmitter` to publish or subscribe events.
Example:
```js
import { createEventBusService } from 'nodejs-event-driven'
const bus = createEventBusService({ type: 'memory' })
await bus.start()
bus.on('hello', (data) => {
console.log('data:', data)
})
bus.send('hello', 'world!')
```
### Getting started
- Install:
```shell
npm i -S nodejs-event-driven
```
- Create `index.js`:
```js
import { createEventBusService } from 'nodejs-event-driven'
import pino from 'pino'
/**
* @type {nodejs-event-driven.Logger}
*/
const logger = pino({
level: 'info',
transport: {
target: 'pino-pretty',
},
})
const run = async () => {
/**
* @type {EventBusServiceConfig}
*/
const config = {
type: 'memory',
logger,
}
const bus = createEventBusService(config)
try {
await bus.start()
await new Promise((resolve) => {
bus.once('foo', (data) => {
logger.info(`received event "foo": ${String(data)}.`)
resolve()
})
logger.info('sending event "foo"…')
bus.send('foo', 'bar')
logger.info('event "foo" sent.')
})
} finally {
await bus.stop()
}
}
void run()
```
- Execute:
```shell
node ./index.js
```
- Expected result:
```shell
[16:23:53.509] INFO (33149): sending event "foo"…
[16:23:53.509] INFO (33149): event "foo" sent.
[16:23:53.510] INFO (33149): received event "foo": bar.
```
### Configuration
Object used in `EventBusService` constructor to pass configuration.
Configuration properties:
- `type` (required): Type of event bus.
Supported values:
- `memory` (default): In memory, without persistence.
- `fs`: File system.
- `redis`: Redis queue.
- `rabbitmq`: RabbitMQ.
- `kafka`: Kafka.
- `logger` (default: no log): Any logger implementation implementing [Logger](https://raw.githubusercontent.com/openhoat/nodejs-event-driven/refs/heads/main/src/main/util/logger.ts) interface.
> All others properties depend on `type` value, matching the following specs:
#### `memory`
- `eventBusMemoryEmitDelay` (default: 0): Duration used to wait (in ms) before sending events.
#### `fs`
- `eventBusFsBaseDataDir` (default: `{tmp-dir}/fs-event-bus`): Base directory used to persist events file structure.
- `eventBusFsPollingDelayMs` (default: 0): Delay of events files polling.
#### `redis`
- `keyPrefix` (default: `events`): Key prefix used to store events in Redis.
- `url` (default: redis default): Redis host URL to connect with.
See [Redis documentation](https://github.com/redis/node-redis) for more information about other configuration properties:
- `database`: Redis database number.
- `name`: Client name.
- `password`: ACL password.
- `username`: ACL username.
#### `rabbitmq`
- `url` (default: rabbitmq default): RabbitMQ host URL to connect with.
#### `kafka`
- `brokers` (default: ['localhost:9092']): Brokers to connect to.
- `clientId` (default: 'app'): Client ID.
- `topicPrefix`: if set, used as a topic prefix (resulting topic becomes `${prefix}-$[topic}`).
### Prerequisite
- Install `redis` NPM dependency to be able to use Redis with `nodejs-event-driven`.
```shell
npm install redis
```
- Install `amqplib` NPM dependency to be able to use RabbitMQ with `nodejs-event-driven`.
```shell
npm install amqplib
```
- Install `kafkajs` NPM dependency to be able to use Kafka with `nodejs-event-driven`.
```shell
npm install kafkajs
```
> `redis`, `amqplib` and `kafkajs` are declared as optional dependencies in `nodejs-event-driven`.
Enjoy!