hardillb / node-red-context-redis

A Node-RED Context store plugin backed by Redis

This is a work in progress.

Redis plugin

The Redis plugin holds context data in the Redis.

Pre-requisite

To run this you need a Redis server running. For details see the Redis site.

Install

1. Run the following command in your Node-RED user directory - typically ~/.node-red

   npm install git+https://github.com/node-red/node-red-context-redis

2. Add a configuration in settings.js:

contextStorage: {
    redis: {
        module: require("node-red-context-redis"),
        config: {
            // see below options
        }
    }
}

Options

This plugin exposes some options defined in node_redis as itself options. It needs following configuration options:

Options	Description
host	The IP address of the Redis server. Default: "127.0.0.1"
port	The port of the Redis server. Default: 6379
db	The Redis logical database to connect. Default: 0
prefix	If set, the string used to prefix all used keys.
password	If set, the plugin will run Redis AUTH command on connect. Note: the password will be sent as plaintext.
tls	An object containing options to pass to tls.connect to set up a TLS connection to the server.
retry_strategy	Specifies a function to reconnect if the connection to Redis is lost.
	default: undefined (Use the default retry strategy)

see https://github.com/NodeRedis/node_redis#options-object-properties

Data Model

Node-RED                      Redis
+-------------------+         +-------------------------------+
| global context    |         | logical database              |
| +---------------+ |         | +---------------------------+ |
| | +-----+-----+ | |         | | +-----------------+-----+ | |
| | | key |value| | | <-----> | | | global:key      |value| | |
| | +-----+-----+ | |         | | +-----------------+-----+ | |
| +---------------+ |         | |                           | |
|                   |         | |                           | |
| flow context      |         | |                           | |
| +---------------+ |         | |                           | |
| | +-----+-----+ | |         | | +-----------------+-----+ | |
| | | key |value| | | <-----> | | | <flow's id>:key |value| | |
| | +-----+-----+ | |         | | +-----------------+-----+ | |
| +---------------+ |         | |                           | |
|                   |         | |                           | |
| node context      |         | |                           | |
| +---------------+ |         | |                           | |
| | +-----+-----+ | |         | | +-----------------+-----+ | |
| | | key |value| | | <-----> | | | <node's id>:key |value| | |
| | +-----+-----+ | |         | | +-----------------+-----+ | |
| +---------------+ |         | +---------------------------+ |
+-------------------+         +-------------------------------+

• This plugin uses a Redis logical database for all context scope.
• This plugin prefixes all used keys with context scope in order to identify the scope of the key.
  • The keys of global context will be prefixed with global: . e.g. Set "foo" to hold "bar" in the global context -> Set "global:foo" to hold "bar" in the Redis logical database.
  • The keys of flow context will be prefixed with <id of the flow>: . e.g. Set "foo" to hold "bar" in the flow context whose id is 8588e4b8.784b38 -> Set "8588e4b8.784b38:foo" to hold "bar" in the Redis.
  • The keys of node context will be prefixed with <id of the node>: . e.g. Set "foo" to hold "bar" in the node context whose id is 80d8039e.2b82:8588e4b8.784b38 -> Set "80d8039e.2b82:8588e4b8.784b38:foo" to hold "bar" in the Redis.

Data Structure

• This plugin converts a value of context to JSON and stores it as string type to the Redis.
• After getting a value from the Redis, the plugin also converts the value to an object or a primitive value.

Node-RED                                 Redis
+------------------------------+         +---------------------------------------------+
| global context               |         | logical database                            |
| +--------------------------+ |         | +-----------------------------------------+ |
| | +--------+-------------+ | |         | | +---------------+---------------------+ | |
| | | str    | "foo"       | | | <-----> | | | global:str    | "\"foo\""           | | |
| | +--------+-------------+ | |         | | +---------------+---------------------+ | |
| | | num    | 1           | | | <-----> | | | global:num    | "1"                 | | |
| | +--------+-------------+ | |         | | +---------------+---------------------+ | |
| | | nstr   | "10"        | | | <-----> | | | global:nstr   | "\"10\""            | | |
| | +--------+-------------+ | |         | | +---------------+---------------------+ | |
| | | bool   | false       | | | <-----> | | | global:bool   | "false"             | | |
| | +--------+-------------+ | |         | | +---------------+---------------------+ | |
| | | arr    | ["a","b"]   | | | <-----> | | | global:arr    | "[\"a\",\"b\"]"     | | |
| | +--------+-------------+ | |         | | +---------------+---------------------+ | |
| | | obj    | {foo,"bar"} | | | <-----> | | | global:obj    | "{\"foo\",\"bar\"}" | | |
| | +--------+-------------+ | |         | | +---------------+---------------------+ | |
| +--------------------------+ |         | +-----------------------------------------+ |
+------------------------------+         +---------------------------------------------+

Other Redis client(e.g. redis-cli) can get the value stored by Node-RED like followings.

Node-RED

global.set("foo","bar","redis");
global.set("obj",{key:"value"},"redis");

redis-cli

redis> GET global:foo
"\"var\""
redis> GET global:obj
"{\"key\":\"value\"}"
redis>