Connects to a redis instance. By default it stores a redis connection handle at server.notes.redis. See below to get a custom DB handle attached to another database.

The redis.ini file has the following sections (defaults shown):

; host=127.0.0.1
; port=6379

; host=127.0.0.1
; port=6379

Publish & Subscribe are DB agnostic and thus have no db setting. If host and port and not defined, they default to the same as [socket] settings.

; see https://github.com/redis/node-redis/blob/HEAD/docs/client-configuration.md
; database=0
; password=battery-horse-staple

Options specified in redis.ini[opts] are applied to the server config, the pubsub config, AND the configurations of any plugins that inherit this plugin. This is ideal if the redis server requires a password. Specify it once in [opts]. If other redis connections need a different value (such as a unique DB), they must specify it. For plugins, all options are stored in the plugins [redis] section of its config file.

Use redis in your plugin like so:

if (server.notes.redis) {
    server.notes.redis.hGetAll(...);
        // or any other redis command
}

In your plugin:

exports.results_init = function (next, connection) {
    this.redis_subscribe(connection, () => {
        connection.notes.redis.on('pmessage', (pattern, channel, message) => {
            this.do_something_with_message(message, ...)
        })
        next()
    })
}
// be nice to redis and disconnect
exports.hook_disconnect = function (next, connection) {
    this.redis_unsubscribe(connection)
}

This variation lets your plugin establish its own Redis connection, optionally with a redis db ID. All redis config options must be listed in your plugins config file in the [redis] section.

exports.register = function () {
    this.inherits('redis');

    this.cfg = this.config.get('my-plugin.ini');

    // populate plugin.cfg.redis with defaults from redis.ini
    this.merge_redis_ini();

    // cluster aware redis connection(s)
    this.register_hook('init_master', 'init_redis_plugin');
    this.register_hook('init_child',  'init_redis_plugin');
}

When a db ID is specified in the [redis] section of a redis inheriting plugin, log messages like these will be emitted when Haraka starts:

[INFO] [-] [redis] connected to redis://172.16.15.16:6379 v3.2.6
[INFO] [-] [limit] connected to redis://172.16.15.16:6379/1 v3.2.6
[INFO] [-] [karma] connected to redis://172.16.15.16:6379/2 v3.2.6
[INFO] [-] [known-senders] connected to redis://172.16.15.16:6379/3 v3.2.6

Notice the database ID numbers appended to each plugins redis connection message.