New in 0.19

The Context Store API provides a pluggable way to configure where context data is stored.

By default, Node-RED uses a memory-based implementation of this API. It also provides a file-based implementation.

To create a custom Context Store, a module should create that implements the Store Module API.

The contextStorage property in settings.js can be used to configure context storage.

It is an object with one or more named context store configurations.

{% highlight javascript %} contextStorage: { default: { module:"memory", config: { customOption: 'value' } } } {% endhighlight %}

Each context store configuration consists of two parts; a module property and a config property.

The module property identifies the context store plugin to use. It can either be the name of built-in module (currently either memory or localfilesystem), or it should be a module that has been loaded using require.

{% highlight javascript %} contextStorage: { default: { module:"memory", }, custom: { module:require("my-custom-store") } } {% endhighlight %}

The config property is an object that is passed to the module to provide an custom options.

A custom plugin's module must export a single constructor function. This function is called when a new instance of the plugin is required. The function is passed the value of the config property for the given instance. This allows the runtime to have multiple instances of the same store plugin, each with its own configuration.

{% highlight javascript %}

var ContextStore = function(config) { this.config = config; }

ContextStore.prototype.open = function() { ... }

module.exports = function(config){ return new ContextStore(config); };

{% endhighlight %}

The object returned by the constructor function must implement all of the functions detailed here.