@ssense/redis-pubsub

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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 });