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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 });