fsm-http

FSM that uses remote HTTP calls to allow state transitions.

Installation

npm install node-fsm-http

Usage

Works as a wrapper node-fsm to allow fsm to use external HTTP requests to check, whether our state transition is valid. Basically, it provides default routerFunc for node-fsm.

In essence, you just provide your machine description the same way as for node-fsm but now you place optional request field to you edge objects:

var machine = {
    "nodes": [
        …
        {
            "name": "B",
            "request": {
                "uri": "http://localhost:8889/stateNotify"
            }
        },
        …
    ],
    "edges": [
        {
            "name": "AB",
            "from": "A",
            "to": "B",
            "request": {
                "uri": "http://localhost:8889/ok" // <- THIS
            }
        }
    ],
    "currentState": "A",
    "data": {
        "arbitraryDataField": "arbitraryDataValue"
    }
}

/// then, you create fsm-http instance without `routerFunc`:
var FSMHttp = require('node-fsm-http');

var fsm = new FSMHttp(machine);

now, you use same methods as for plain node-fsm, but when you attempt to change machine state, fsm performs http request specified by request field of edge object you trying to follow. If http request returns HTTP status 200, transition successfull, otherwise it fails.

node-fsm-http uses request module to perform HTTP request, using request value as option value for request (module), so you have many options to pass data from your fsm to external endpoints (see 'request' documentation on 'options' object), for example, you could specify different HTTP verbs to perform request, or provide request payload to pass form data to external HTTP endpoint, etc.

If egge you trying to follow doesn't have request field, fsm decides that transition is successful by default.

Passing fsm's data during request

Your fsm may have data field specified. When fsm makes http request to check, whether it can change it state, data field value is mixed with json field of request property place on your fsm graph edge (data members takes precedence over values specified in request field).

Passing requestData upon request

Fsm's .follow() method can take arbitrary data as second parameter. These data will be passed during external HTTP request in requestData field.

Note: Assigning requestData field made after mixing data field with request property of the edge we follow. So don't use requestData as a part of your machine since it will be always overwritten on state change request processing.

Updating fsm's data

If reqest for changing fsm state returns 'application/json' content type, json document it's containing got parsed, and fsm's data field is overwritten with this new value. This allows your http endpoint to alter your fsm data on the go.

State change HTTP notification

State objects could also have request field. If specified, we make asynchronous HTTP request using this value as request() options object (same approach as for edge).

Important: Regardless of this call result, machine will not change it state, even if remote enpoint returned error code.

Changelog

3.0.0

Support passing requestData to external HTTP endpoint as a part of external HTTP request. It may break you code, for prior versions.