Context Store API

New in 0.19

A Context Storage plugin is a node.js module that exposes a function on its module.exports that can be used to create new instances of the plugin. The object returned by the function must have the following functions:

Function	Description
ContextStore.open()	Open the storage ready for use
ContextStore.close()	Close the storage
ContextStore.get(scope, key, callback)	Get values from the store
ContextStore.set(scope, key, value, callback)	Set values in the store
ContextStore.keys(scope, callback)	Get a list of all keys in the store
ContextStore.delete(scope)	Delete all keys for a given scope
ContextStore.clean(activeNodes)	Clean the context store

ContextStore.open()

Open the storage ready for use. This is called before any store values are accessed.

Returns a Promise that resolves when the store is ready for access.

ContextStore.close()

Called when the runtime is stopped so no further key values will be accessed.

Returns a Promise that resolves with the store is closed.

ContextStore.get(scope, key, [callback])

Argument	Description
scope	the scope of the key
key	the key, or array of keys, to return the value(s) for.
callback	optional a callback function to invoke with the key value

The key argument can be either a String identifying a single key, or an Array of Strings identifying multiple keys to return the values for.

If the optional callback argument is provided, it must be a function that takes two or more arguments:

function callback(error, value1, value2, ... ) {
}

If no callback is provided, and the store supports synchronous access, the get function should return the individual value, or array of values for the keys. If the store does not support synchronous access it should throw an error.

ContextStore.set(scope, key, value, [callback])

Argument	Description
scope	the scope of the key
key	the key, or array of keys, to set the value(s) for.
value	the value, or array of values
callback	optional a callback function to invoke when the value is set

The key argument can be either a String identifying a single key, or an Array of Strings identifying multiple keys to set.

`key`	`value`	Action
String	Any	Stores `value` under `key`
Array	Array	Stores each element of the `value` array under the corresponding `key` value. If `value` has fewer elements than `key`, it sets the missing values to `null`.
Array	not-Array	Stores `value` as the value of the first key - uses `null` for any remaining keys.

If the optional callback argument is provided, it will be called when the value has been stored. It takes a single argument, error, to indicate any errors hit whilst storing the values.

function callback(error) {
}

If no callback is provided, and the store supports synchronous access, the set function should return once the value is stored. If the store does not support synchronous access it should throw an error.

ContextStore.keys(scope, [callback])

Argument	Description
scope	the scope of the keys to return
callback	optional a callback function to invoke with the list of keys

Gets a list of all keys under the given scope.

If the optional callback argument is provided, it must be a function that takes two or more arguments:

function callback(error, keys) {
}

If no callback is provided, and the store supports synchronous access, the keys function should return the array of keys. If the store does not support synchronous access it should throw an error.

ContextStore.delete(scope)

Argument	Description
scope	the scope to delete

ContextStore.clean(activeNodes)

Argument	Description
activeNodes	a list of all node/flow ids that are still active

Returns a promise that resolves when store has removed any context scopes that are no longer required. The activeNodes list can be used to identify what nodes and flows are still considered active.

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