stashback

    1.1.3 • Public • Published

    Stashback

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    Stashback is a library for stashing and retrieving callbacks in a decoupled request/response workflow. Its primary use case is to enable code within an http request/response sequence to publish a message to an ESB, e.g. RabbitMQ and wait for a reply.

    Installation

    npm install stashback

    Example Usage (Express)

    var rabbitmq = require('./my-rabbitmq-client')
    var express = require('express')
    var format = require('util').format
    var uuid = require('node-uuid').v4
    var stashback = require('stashback')({ timeout: 5000 })
     
    var app = express()
     
    app.get('/greet/:id', function(req, res, next) {
     
        // Generate a unique id for the callback
        var callbackId = uuid()
     
        // Define the callback
        var callback = function(err, user) {
            if (err) return next(err)
            res.send(format('Hello %s', user.name))
        }
     
        // Stash the callback for later execution
        stashback.stash(callbackId, callback, function(err) {
     
            // An error will occur if you've used a duplicate callbackId.
            if (err) return next(err)
     
            // Publish the message to the ESB, requesting user for the specified id. Using rabbitmq as an example.
            rabbitmq.publish({ callbackId: callbackId, userId: req.params.id })
        })
    })
     
    app.listen(3000)
     
     
    function onMessage(message) {
     
        // When we receive the user response unstash the callback using the callbackId specified in the message
        stashback.unstash(message.callbackId, function(err, callback) {
     
            // Execute the callback passing it the user object (the callback will be a no-op if something went wrong)
            callback(err, message.user)
        })
    }

    Callback Expiry

    In order to prevent a slow memory leak and to abort slow running requests it's a good idea to configure stashback with a timeout. This can be done globally and for each 'stash' operation. See the api for more details.

    Duplicates

    Attempting to 'stash' multiple callbacks with the same id results in an error. Attempting to 'unstash' a callback twice (or after it has expired) results in both an error and a no-op callback being returned. i.e.

    stashback.unstash('never-stashed-or-expired', function(err, callback) {
        assert.equal(err.message, 'Unknown key: never-stashed-or-expired')
        assert.equal(typeof callback, 'function')
    })

    Further Customisation

    You can further customise stashback's behaviour by providing your own onDuplicateKey, onUnknownKey and onExpiry handlers. See the api for more details.

    Install

    npm i stashback

    DownloadsWeekly Downloads

    10,253

    Version

    1.1.3

    License

    ISC

    Unpacked Size

    21.6 kB

    Total Files

    15

    Last publish

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