2.0.1 • Published 1 year ago
@ssense/redis-pubsub v2.0.1
Redis Pub/Sub
class RedisPubSub
RedisPubSub allows to quickly set up a client which supports the Redis pub/sub protocol. (see examples here)
Methods
| Method | Returns | Description |
|---|---|---|
constructor(connection: RedisPubSubConnectionOptions) | RedisPubSub | Creates a new instance of RedisPubSub |
on(event: string, listener: (message: PubSubMessage) => void) | RedisPubSub | Registers to a Redis topic, adding a listener called when a pub/sub event is received |
on(event: 'error', listener: (err: Error) => void) | RedisPubSub | Adds a listener called when an error occurs in the underlying RedisPubSub |
emit(topic: string, message: any) | Promise<void> | Sends a message on Redis pub/sub for a given topic |
Details
constructor(connection: RedisPubSubConnectionOptions)
Creates a new instance of RedisPubSub
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| connection | RedisPubSubConnectionOptions | Yes | The parameters used to connect to the Redis pub/sub server |
RedisPubSubConnectionOptions properties
| Name | Type | Required | Description |
|---|---|---|---|
| host | string | Yes | Redis server hostname or IP address |
| port | number | No | Redis server port (default: 6379) |
| password | string | No | Password for Redis server if any (default: undefined) |
| tlsEnabled | boolean | No | Enable TLS connection (default: false) |
| compressionEnabled | boolean | No | Enable compression (default: false) |
| password | string | No | Password for Redis server if any (default: undefined) |
| mode | 'read'|'write' | No | Used to save resources, by avoiding extra connections to Redis if your application only needs to read or write to the pub/sub system.Do not set to get a bi-directional connection (read & write, which is the default).Use read to use a read-only connection (if used, the emit method will be deactivated).Use write to use a write only connection (if used, the on method will be deactivated, except for the error event). |
on(event: string, listener: (message: PubSubMessage) => void)
Registers to a Redis topic, adding a listener called when a pub/sub event is received
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| event | string | Yes | Redis topic name, you can listen to multiple topics at once using a pattern, eg: *:Created |
| listener | Function | Yes | Function which will be called when a message is received, will be provided a PubSubMessage object |
PubSubMessage properties
| Name | Type | Required | Description |
|---|---|---|---|
| topic | string | Yes | Redis topic on which the message has been sent |
| data | any | Yes | Message data (any object) |
Return value
| Type | Description |
|---|---|
RedisPubSub | The current RedisPubSub instance |
on(event: 'error', listener: (err: Error) => void)
Adds a listener called when an error occurs in the underlying RedisPubSub
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| event | 'error' | Yes | The 'error' string |
| listener | Function | Yes | Function which will be called on RedisPubSub error, will be provided an Error object |
Return value
| Type | Description |
|---|---|
RedisPubSub | The current RedisPubSub instance |
emit(topic: string, message: any)
Sends a message on Redis pub/sub for a given topic
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| topic | string | Yes | Valid topic name (eg: 'Product:Product:Created') |
| message | any | Yes | Content of the message to send, can be any object (needs to be JSON.stringifiable) |
Examples
import { RedisPubSub } from '@ssense/redis-pubsub';
// Instantiate the client with the minimum required parameters
const client = new RedisPubSub({ host: 'localhost' });
// Register to a simple topic
client.on('Product:Product:Created', (message) => {
console.log(message);
// Will display: {topic: 'Product:Product:Created', data: {id: 123456789}}
});
// Register using a pattern, to listen to multiple topics at once
client.on('*:Created', (message) => {
console.log(message);
// Will display: {topic: 'Product:Product:Created', data: {id: 123456789}}
});
// Register to a special "error" topic, called if an internal error occurs in the RedisPubSub class
client.on('error', (err: Error) => {
// Manage the error
console.error('An error occurred', err);
});
// Send a message on a specific topic, which will trigger the two listeners above
client.emit('Product:Product:Created', { id: 123456789 });
// Send a message on another topic, which will only trigger the second listener above
client.emit('Product:Brand:Created', { id: 123456789 });