Overview

  • Hull Client > Most low level Hull Platform API client: const hull = new Hull({ configuration })
  • Hull Middleware > A bridge between Hull Client and a NodeJS HTTP application (e.g. express) which initializes context for every HTTP request: > app.use(Hull.Middleware({ configuration }))
  • Hull Connector > A complete toolkit to operate with Hull Client in request handlers. Includes Hull Middleware and a set of official patterns to build highly scalable and efficient Connectors: > const connector = new Hull.Connector({ configuration })

hull node core components


Hull.Middleware

This middleware standardizes the instantiation of a Hull Client in the context of authorized HTTP request. It also fetches the entire ship's configuration.

Example usage:

import Hull from "hull";
import express from "express";

const app = express();
app.use(Hull.Middleware({ hostSecret: "secret" }));
app.post("/show-segments", (req, res) => {
    req.hull.client.get("/segments")
        .then((segments) => {
            res.json(segments)
        });
});

Options

  • hostSecret

    The ship hosted secret - consider this as a private key which is used to encrypt and decrypt req.hull.token. The token is useful for exposing it outside the Connector <-> Hull Platform communication. For example the OAuth flow or webhooks. Thanks to the encryption no 3rd party will get access to Hull Platform credentials.

  • clientConfig

    Additional config which will be passed to the new instance of Hull Client

Basic Context Object

The Hull Middleware operates on req.hull object. It uses it to setup the Hull Client and decide which configuration to pick - this are the core parameters the Middleware touches:

  • req.hull.config > an object carrying id, secret and organization. You can setup it prior to the Hull Middleware execution (via custom middleware) to ovewrite default configuration strategy
  • req.hull.token

    an encrypted version of configuration. If it's already set in the request, Hull Middleware will try to decrypt it and get configuration from it. If it's not available at the beginning and middleware resolved the configuration from other sources it will encrypt it and set req.hull.token value.

    When the connector needs to send the information outside the Hull ecosystem it must use the token, not to expose the raw credentials. The usual places where it happens are:

    • dashboard pane links
    • oAuth flow (callback url)
    • external webhooks
  • req.hull.client

    Hull API client initialized to work with current organization.

  • req.hull.ship

    ship object with manifest information and private_settings fetched from Hull Platform.

  • req.hull.hostname

    Hostname of the current request. Since the connector are stateless services this information allows the connector to know it's public address.

Operations - configuration resolve strategy

Here is what happens when your Express app receives a query.

  1. If a config object is found in req.hull.config steps 2 and 3 are skipped.
  2. If a token is present in req.hull.token, the middleware will try to use the hostSecret to decrypt it and set req.hull.config.
  3. If the query string (req.query) contains id, secret, organization, they will be stored in req.hull.config.
  4. After this, if a valid configuration is available in req.hull.config, a Hull Client instance will be created and stored in req.hull.client.
  5. When this is done, then the Ship will be fetched and stored in req.hull.ship > If there is a req.hull.cache registered in the Request Context Object, it will be used to cache the ship object. For more details see Context Object Documentation
  6. If the configuration or the secret is invalid, an error will be thrown that you can catch using express error handlers.

Hull.Connector

The connector is a simple HTTP application served from public address. It could be implemented in any way and in any technological stack unless it implements the same API:

const app = express();
app.get("/manifest.json", serveTheManifestJson);
app.listen(port);

Yet to ease the connector development and to extract common code base the hull-node library comes with the Hull.Connector toolkit which simplify the process of building new connector by a set of helpers and utilities which follows the same convention.

Initialization

import Hull from "hull";

const connector = new Hull.Connector({
    port: 1234, // port to start express app on
    hostSecret: "secret",  // a secret generated random string used as a private key
    segmentFilterSetting: "synchronized_segments" // name of the connector private setting which has information about filtered segments
});

This is the instance of the Connector module which exposes a set of utilities which can be applied to the main express app. The utilities can be taken one-by-one and applied the the application manually or there are two helper method exposed which applies everything be default:

Setup Helpers

Setup Helpers are two high-level methods exposed by initialized Connector instance to apply custom middlewares to the Express application. Those middlewares enrich the application with connector features.

import express from "express";
import Hull from "hull";

const app = express();
const connector = new Hull.Connector({ hostSecret });

connector.setupApp(app); // apply connector related features to the application
app.post("/fetch-all", (req, res) => {
  res.end("ok");
});
connector.startApp(app, port); // internally calls app.listen

setupApp(express app)

This method applies all features of Hull.Connector to the provided application:

  • serving /manifest.json, /readme and / endpoints
  • serving static assets from /dist and /assets directiories
  • rendering /views/*.html files with ejs renderer
  • timeouting all requests after 25 seconds
  • adding Newrelic and Sentry instrumentation
  • initiating the wole Context Object
  • handling the hullToken parameter in a default way

startApp(express app)

This is a supplement method which calls app.listen internally and also terminates instrumentation of the application calls.

Bare express application

If you prefer working with the express app directly and have full control over how modules from Hull.Connector alter the behaviour of the application, you can pick them directly. Calling the setupApp and startApp is effectively equal to the following setup:

import { renderFile } from "ejs";
import timeout from "connect-timeout";
import { staticRouter } from "hull/lib/utils";

app.engine("html", renderFile); // render engine
app.set("views", `${process.cwd()}/views`);
app.set("view engine", "ejs");

app.use(timeout("25s")); // make sure that we will close the connection before heroku does
app.use(connector.instrumentation.startMiddleware()); // starts express app instrumentation
app.use(connector.instrumentation.contextMiddleware()); // adds `req.hull.metric`
app.use(connector.queue.contextMiddleware()); // adds `req.hull.enqueue`
app.use(connector.cache.contextMiddleware()); // adds `req.hull.cache`
app.use((req, res, next) => {
    // must set `req.hull.token` from request
    req.hull.token = req.query.hullToken;
});
app.use(connector.notifMiddleware()); // parses the incoming sns message, so the clientMiddleware knows if to bust the cache
app.use(connector.clientMiddleware()); // sets `req.hull.client` and `req.hull.ship`
app.use("/", staticRouter());

// add your routes here:
app.post("/fetch-all", (req, res) => {
  res.end("ok");
});


app.use(connector.instrumentation.stopMiddleware()); // stops instrumentation
// start the application
app.listen(port, () => {
});

Here somes the detailed description of the utilities.

notifMiddleware()

Runs bodyParser.json() and if the incoming requests is a Hull notification it verifies the incoming data and set req.hull.message with the raw information and req.hull.notification with parsed data.

clientMiddleware()

This is a wrapper over Hull.Middleware whith hostSecret and other configuration options bound. The middleware initializes the Hull API client: req.hull.client = new Hull({}); using credentials from (in order) req.hull.config, req.hull.token req.hull.query.

instrumentation.contextMiddleware()

Adds req.hull.metric for details see Context Object documentation.

queue.contextMiddleware()

Adds req.hull.enqueue for details see Context Object documentation.

cache.contextMiddleware()

Adds req.hull.cache for details see Context Object documentation.

instrumentation.startMiddleware()

Instrument the requests in case of exceptions. More details about instrumentation here.

instrumentation.stopMiddleware()

Instrument the requests in case of exceptions. More details about instrumentation here.

Worker

More complex connector usually needs a background worker to split its operation into smaller tasks to spread the workload:

import express from "express";
import Hull from "hull";

const app = express();

const connector = new Hull.Connector({ hostSecret });
// apply connector related features to the application
connector.setupApp(app);

connector.worker({
    customJob: (ctx, payload) => {
        // process payload.users
    }
})
app.post("/fetch-all", (req, res) => {
    req.hull.enqueue("customJob", { users: [] });
});
connector.startApp(app, port);
connector.startWorker(queueName = "queueApp");

Infrastructure

The connector internally uses infrastructure modules to support its operation: - Instrumentation (for metrics) - Queue (for internal queueing purposes) - Cache (for caching ship object and segment lists) - Batcher (for internal incoming traffing grouping)

Read more how configure them.

Utilities

Above documentation shows the basic how to setup and run the Hull.Connector and the express application. To implement the custom connector logic, this library comes with a set of utilities to perform most common operations.

Here is the full list >>

Custom middleware

The Hull.Connector architecture gives a developer 3 places to inject custom middleware:

  1. At the very beginning of the middleware stack - just after const app = express(); - this is a good place to initialy modify the incoming request, e.g. set the req.hull.token from custom property
  2. After the Context Object is built - after calling setupApp(app) - all context object would be initiated, but req.hull.client, req.hull.segments and req.hull.ship will be present only if credentials are passed. To ensure the presence of these properties requireHullMiddleware can be used.
  3. Before the closing startApp(app) call which internally calls app.listen()

NOTE: every Handler provided by this library internally uses requireHullMiddleware and responseMiddleware to wrap the provided callback function. Have it in mind while adding custom middlewares at the app and router level.


Context object

Hull.Connector and Hull.Middleware applies multiple middlewares to the request handler. The result is req.hull object which is the Context Object - a set of modules to work in the context of current organization and connector instance.

The core part of the Context Object is described in Hull Middleware documentation.

{
  // set by Hull.Middleware
  config: {},
  token: "",
  client: {
    logger: {},
  },
  ship: {},
  hostname: req.hostname,
  params: req.query + req.body,

  // set by Hull.Connector
  connectorConfig: {},
  segments: [],
  cache: {},
  enqueue: () => {},
  metric: {},
  helpers: {},
  service: {},
  message: {},
  notification: {}
}
  • connectorConfig

    Hash with connector settings, details here

  • segments

    An array of segments defined at the organization, it's being automatically exposed to the context object json [{ name: "Segment name", id: "123abc" }]

  • cache

    Since every connector can possibly work on high volumes of data performing and handling big number of requests. Internally the cache is picked by the Hull Middleware to store the ship object and by segmentsMiddleware to store segments list. The cache can be also used for other purposes, e.g. for minimizing the External API calls. Caching Module is exposing three public methods: js ctx.cache.get("object_name"); ctx.cache.set("object_name", object_value); ctx.cache.wrap("object_name", () => { return Promise.resolve(object_value) });

  • enqueue

    A function added to context by Queue Module. It allows to perform tasks in an async manner. The queue is processed in background in a sequential way, it allows to:

    • respond quickly in the express application actions (they just queue the work)
    • split the workload into smaller chunks (e.g. for extract parsing)
    • control the concurrency - most of the SERVICE APIs have rate limits
    • options.queueName - when you start worker with a different queue name, you can explicitly set it here to queue specific jobs to that queue
  req.hull.enqueue("jobName", { user: [] }, options = {});
  • metric > An object added to context by Instrumentation Module. It allows to send data to metrics service. It's being initiated in the right context, and expose following methods:
  req.hull.metric.value("metricName", metricValue = 1);
  req.hull.metric.increment("metricName", incrementValue = 1); // increments the metric value
  req.hull.metric.event("eventName", { text = "", properties = {} });
  • helpers

    A set of functions from connector/helpers bound to current Context Object. More details here. js req.hull.helpers.filterUserSegments(); req.hull.helpers.requestExtract(); req.hull.helpers.setUserSegments();

  • service

    A namespace reserved for connector developer to inject a custom logic. When the connector base code evolves, the best technique to keep it maintainable is to split it into a set of functions or classes. To make it even simpler and straightforward the connector toolkit uses one convention to pass the context into the functions and classes. The service namespace is reserved for the purpose and should be used together with use method on connector instance to apply custom middleware. That should be an object with custom structure adjusted to specifi connector needs and scale:

Example:

  connector.use((req, res, next) => {
    req.hull.service = {
      customFunction: customFunction.bind(req.hull),
      customModule: new CustomClass(req.hull) 
    };
    next();
  });

  connector.setupApp(app);

  app.get("/action", serviceMiddleware(service), (req, res) => {
    const { service } = req.hull;
    service.customFunction(req.query.user_id);
    // or
    service.customModule.customMethod(req.query.user_id);
  });
  • message

    Optional - set if there is a sns message incoming. It contains raw, message object - should not be used directly by the connector, req.hull.notification is added for that purpose. js Type: "Notification", Subject: "user_report:update", Message: "{\"user\":{}}"

  • notification

    Optional - if the incoming sns message type if Notification, then the messaged is parsed and set to notification. It has following structure: js subject: "user_report:update", timestamp: new Date(message.Timestamp), paload: { user: {} }

Context management convention

The context object is treated by the Hull.Connector as a dependency injection container which carries on all required dependencies to be used in actions, jobs or custom methods.

This library sticks to a the following convention of managing the context object:

Functions

Every "pure" function which needs context to operate takes it as a first argument:

function getProperties(context, prop) {
  cons { client } = context;
  return client.get("/properties", { prop });
}

This allow binding functions to the context and using bound version:

const getProp = getProperties.bind(null, context);

getProp("test") === getProperties(context, "test")

Classes

In case of class the context is the one and only argument:


class ServiceAgent {
  constructor(context) {
    this.client = context.client;
  }
}

Helpers

This is a set of additional helper functions being exposed at req.hull.helpers. They allow to perform common operation in the context of current request. They are similar o req.hull.client.utils, but operate at higher level, ensure good practises and should be used in the first place before falling back to raw utils.

updateSettings()

Allows to update selected settings of the ship private_settings object. This is a wrapper over hull.utils.settings.update() call. On top of that it makes sure that the current context ship object is updated, and the ship cache is refreshed.

req.hull.helpers.updateSettings({ newSettings });

requestExtract()

This is a method to request an extract of user base to be sent back to the Connector to a selected path which should be handled by notifHandler.

req.hull.helpers.requestExtract({ segment = null, path, fields = [], additionalQuery = {} });

Context

Helpers are just a set of simple functions which take Context Object as a first argument. When being initialized by Hull.Middleware their are all bound to the proper object, but the functions can be also used in a standalone manner:

import { updateSettings } from "hull/lib/helpers";

app.post("/request", (req, res) => {
  updateSettings(req.hull, { called: true });
  // or:
  req.hull.helpers.updateSettings({ called: true });
});

Infrastrcture

Production ready connectors needs some infrascture modules to support its operations, allow instrumentation, queueing and caching. The Hull.Connector comes with default settings, but also allows to initiate them and set a custom configuration:

const instrumentation = new Instrumentation();
const cache = new Cache();
const queue = new Queue();

const connector = new Hull.Connector({ instrumentation, cache, queue });

Queue

By default it's initiated inside Hull.Connector as a very simplistic in-memory queue, but in case of production grade needs, it comes with a Kue adapter which you can initiate in a following way:

import { Queue } from "hull/lib/infra";

const queue = new Queue("kue", { options });

const connector = new Hull.Connector({ queue });

Options from the constructor of the Queue are passed directly to the kue.createQueue() method and can be set with following parameters: https://github.com/Automattic/kue#redis-connection-settings

The queue instance has a contextMiddleware method which adds req.hull.enqueue method to queue jobs - this is done automatically by Hull.Connector().setupApp(app):

req.hull.enqueue(jobName = "", jobPayload = {}, options = {});

options: 1. ttl - milliseconds > Job producers can set an expiry value for the time their job can live in active state, so that if workers didn't reply in timely fashion, Kue will fail it with TTL exceeded error message preventing that job from being stuck in active state and spoiling concurrency. 2. delay - milliseconds > Delayed jobs may be scheduled to be queued for an arbitrary distance in time by invoking the .delay(ms) method, passing the number of milliseconds relative to now. Alternatively, you can pass a JavaScript Date object with a specific time in the future. This automatically flags the Job as "delayed". 3. priority - integer / string: js { low: 10, normal: 0, medium: -5, high: -10, critical: -15 }

By default the job will be retried 3 times and the payload would be removed from queue after successfull completion.

Then the handlers to work on a specific jobs is defined in following way:

connector.worker({
    jobsName: (ctx, jobPayload) => {
        // process Payload
        // this === job (kue job object)
        // return Promise
    }
});
connector.startWorker();

Cache

The default comes with the basic in-memory store, but in case of distributed connectors being run in multiple processes for reliable operation a shared cache solution should be used. The Cache module internally uses node-cache-manager, so any of it's compatibile store like redis or memcache could be used:

import redisStore from "cache-manager-redis";
import { Cache } from "hull/lib/infra";

const cache = new Cache({
    store: redisStore,
    url: 'redis://:XXXX@localhost:6379/0?ttl=600'
});

const connector = new Hull.Connector({ cache });

The cache instance also exposes contextMiddleware whch adds req.hull.cache to store the ship and segments information in the cache to not fetch it for every request. The req.hull.cache is automatically picked and used by the Hull.Middleware and segmentsMiddleware.

The req.hull.cache can be used by the connector developer for any other caching purposes:

ctx.cache.get("object_name");
ctx.cache.set("object_name", object_value);
ctx.cache.wrap("object_name", () => {
    return Promise.resolve(object_value)
});

There are two object names which are reserved and cannot be used here:

  • any ship id
  • "segments"

IMPORTANT internal caching of ctx.ship object is refreshed on ship:update notifications, if the connector doesn't subscribe for notification at all the cache won't be refreshed automatically. In such case disable caching, set short TTL or add notifHandler.

Instrumentation

It automatically sends data to DataDog, Sentry and Newrelic if appropriate ENV VARS are set:

  • NEW_RELIC_LICENSE_KEY
  • DATADOG_API_KEY
  • SENTRY_URL

It also exposes the contextMiddleware which adds req.hull.metric agent to add custom metrics to the ship. Right now it doesn't take any custom options, but it's showed here for the sake of completeness.

import { Instrumentation } from "hull/lib/infra";

const instrumentation = new Instrumentation();

const connector = new Connector.App({ instrumentation });

Handling the process shutdown

Two infrastrcture services needs to be notified about the exit event:

  • Queue - to drain and stop the current queue processing
  • Batcher - to flush all pending data.

Connector Utilities

In addition to the Connector toolkit the library provides a variety of the utilities to perform most common actions of the ship. Following list of handlers and middleware helps in performing most common connector operations.

actionHandler()

This is the simplest requests handler to expose custom logic through an API POST endpoint. The possible usage is triggering a custom operation (like fetching historical data) or a webhook. Both cases handle incoming flow data into Hull platform. However in case of busy webhook it's better to use batcherHandler which automatically group the incoming requests into batches.

import { actionHandler } from "hull/lib/utils";
const app = express();

app.use("/fetch-all", actionHandler((ctx, { query, body }) => {
  const { client, ship } = ctx;

  const { api_token } = ship.private_settings;
  const serviceClient = new ServiceClient(api_token);
  return serviceClient.getHistoricalData()
    .then(users => {
      users.map(u => {
        client.asUser({ email: u.email }).traits({
          new_trait: u.custom_value
        });
      });
    });
}));

batcherHandler()

The second incoming handler which works in a simillar way as actionHandler but it also groups incoming requests into batches of selected size:

import { batcherHandler } from "hull/lib/utils";
const app = express();

app.use("/fetch-all", batcherHandler((ctx, requests) => {
  requests.map(request => {
    console.log(request); // { query, body }
  })
}, {
  maxSize: 100, // maximum size of the batch
  maxTime: 1000 // time time in milliseconds to flush batch after the first item came in
}));

notifHandler()

NotifHandler is a packaged solution to receive User and Segment Notifications from Hull. It's built to be used as an express route. Hull will receive notifications if your ship's manifest.json exposes a subscriptions key:

{
  "subscriptions" : [ { "url" : "/notify" } ]
}

Here's how to use it.

import { notifHandler } from "hull/lib/utils";
const app = express();

const handler = NotifHandler({
  userHandlerOptions: {
    groupTraits: true, // groups traits as in below examples
    maxSize: 6,
    maxTime: 10000,
    segmentFilterSetting: "sychronized_segments"
  },
  onSubscribe() {} // called when a new subscription is installed
  handlers: {
    "ship:update": function(ctx, message) {},
    "segment:update": function(ctx, message) {},
    "segment:delete": function(ctx, message) {},
    "user:update": function(ctx, messages = []) {
      console.log('Event Handler here', ctx, messages);
      // ctx: Context Object
      // messages: [{
      //   user: { id: '123', ... },
      //   segments: [{}],
      //   changes: {},
      //   events: [{}, {}]
      //   matchesFilter: true | false
      // }]
    }
  }
})

connector.setupApp(app);
app.use('/notify', handler);

For example of the notifications payload see details

Extracts

In addition to event notifications Hull supports sending extracts of userbase. These extracts can be triggered via Dashboard manual user action or can be programiatically requested from Connector logic (see requestExtract helper). The Connector will receive manual batches if your ship's manifest.json exposes a batch tag in tags:

{
  "tags" : [ "batch" ]
}

In both cases the batch extract is handled by the user:update. The extract is split into smaller chunks using the userHandlerOptions.maxSize option. In extract every message will contain only user and segments information.

In addition to let the user:update handler detect whether it is processing a batch extract or notifications there is a third argument passed to that handler - in case of notifications it is undefined, otherwise it includes query and body parameters from req object.

oAuthHandler()

OAuthHandler is a packaged authentication handler using Passport. You give it the right parameters, it handles the entire auth scenario for you.

It exposes hooks to check if the ship is Set up correctly, inject additional parameters during login, and save the returned settings during callback.

Here is how to use it:

import { oAuthHandler } from "hull/lib/utils";
import { Strategy as HubspotStrategy } from "passport-hubspot";

const app = express();

app.use("/auth", oAuthHandler({
  name: "Hubspot",
  tokenInUrl: true,
  Strategy: HubspotStrategy,
  options: {
    clientID: "xxxxxxxxx",
    clientSecret: "xxxxxxxxx", //Client Secret
    scope: ["offline", "contacts-rw", "events-rw"] //App Scope
  },
  isSetup(req) {
    if (!!req.query.reset) return Promise.reject();
    const { token } = req.hull.ship.private_settings || {};
    return (!!token) ? Promise.resolve({ valid: true, total: 2}) : Promise.reject({ valid: false, total: 0});
  },
  onLogin: (req) => {
    req.authParams = { ...req.body, ...req.query };
    return req.hull.client.updateSettings({
      portalId: req.authParams.portalId
    });
  },
  onAuthorize: (req) => {
    const { refreshToken, accessToken } = (req.account || {});
    return req.hull.client.updateSettings({
      refresh_token: refreshToken,
      token: accessToken
    });
  },
  views: {
    login: "login.html",
    home: "home.html",
    failure: "failure.html",
    success: "success.html"
  },
}));

To make it working in Hull dashboard set following line in manifest.json file:

{
  "admin" : "/auth/",
}

parameters:

  • name > The name displayed to the User in the various screens.
  • tokenInUrl > Some services (like Stripe) require an exact URL match. > Some others (like Hubspot) don't pass the state back on the other hand. > > Setting this flag to false (default: true) removes the token Querystring parameter in the URL to only rely on the state param.
  • Strategy > A Passport Strategy.
  • options > Hash passed to Passport to configure the OAuth Strategy. (See Passport OAuth Configuration)
  • isSetup() > A method returning a Promise, resolved if the ship is correctly setup, or rejected if it needs to display the Login screen. > > Lets you define in the Ship the name of the parameters you need to check for. > > You can return parameters in the Promise resolve and reject methods, that will be passed to the view. This lets you display status and show buttons and more to the customer
  • onLogin() > A method returning a Promise, resolved when ready. > > Best used to process form parameters, and place them in req.authParams to be submitted to the Login sequence. Useful to add strategy-specific parameters, such as a portal ID for Hubspot for instance.
  • onAuthorize() > A method returning a Promise, resolved when complete. > Best used to save tokens and continue the sequence once saved.
  • views > Required, A hash of view files for the different screens. > Each view will receive the following data: js views: { login: "login.html", home: "home.html", failure: "failure.html", success: "success.html" } //each view will receive the following data: { name: "The name passed as handler", urls: { login: '/auth/login', success: '/auth/success', failure: '/auth/failure', home: '/auth/home', }, ship: ship //The entire Ship instance's config }

requireHullMiddleware

The middleware which ensures that the Hull Client was successfully setup by the Hull.Middleware:

import { requireHullMiddleware } from "hull/lib/utils";
const app = express();

app.post(
  "/fetch",
  Hull.Middleware({ hostSecret }),
  requireHullMidlleware,
  (req, res) => {
    // we have a guarantee that the req.hull.client
    // is properly set.
    // In case of missing credentials the `requireHullMidlleware`
    // will respond with 403 error
  }
);

responseMiddleware

This middleware helps sending a HTTP response and can be easily integrated with Promise based actions:

Normally one would need to do:

const app = express();

app.post("fetch", ...middleware, (req, res) => {
  performSomeAction()
    .then(
      () => res.end("ok"),
      (err) => {
        req.hull.client.logger.error("fetch.error", err.stack || err);
        res.status(500).end();
      }
    );
});

The response middleware takes that instrastructure related code outside, so the action handler can focus on the logic only. It also makes sure that both Promise resolution are handled properly:

import { responseMiddleware } from "hull/lib/utils";
const app = express();

app.post("fetch", ...middleware, (req, res, next) => {
  performSomeAction()
    .then(next, next);
}, responseMiddleware);