REACTIVE PROGRAMMING & IOT: A PERFECT MARRIAGE Sven Beauprez, IoTBE.org

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•  Steering member of IoT BE -  http://www.iotbe.org -  http://www.meetup.com/iot_be/

•  Steering member of JavaPolis/Devoxx (2002 – 2009)

•  Enterprise Solution Architect & Integration Architect •  Entrepreneur & Evangelist of cutting edge internet technologies

-  In the middle of founding several startups around IoT

•  Keep in touch -  sven.beauprez@iotbe.org -  https://www.linkedin.com/in/svenbeauprez -  @SvenBeauprez and @iot_bE

WHO AM I?

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•  One of the larger IoT communities in Europe (>850 members) -  http://www.iotbe.org -  http://www.meetup.com/iot_be/

•  Regular meetups around IoT and providing guest speakers for international conferences

•  We are looking for international partners for EU Funding (Horizon 2020 Funding)!

•  We are always looking for experienced (international) speakers for our meetups!

IOT BE

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IOT WORLD FORUM REFERENCE MODEL

1. Physical devices (the “Edge”)

2. Connectivity

3. Edge computing (the “Fog”)

4. Data Accumulation 5. Data Abstraction

(in the “Cloud”)

6. Application

7. Collaboration & Processes

Actuators and sensors send and receive data via

sending or receiving it via the internet to/from

(big) data stores from which data can be retrieved or stored

so people can act upon it

by devices where it is processed and visualised

via the internet

gateways which filters and aggregates it before

a network towards

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INTERNET OF THINGS VS. INTERNET OF EVERYTHING

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INTERNET OF THINGS VS. INTERNET OF EVERYTHING

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•  … runs as a single process -  Does not start a new process for each new request, which would mean a lot of overhead

•  … runs applications in a single thread -  Does not start a new thread for each new request, which means less complex code and

avoiding race conditions

•  … is asynchronous -  Can handle multiple requests at one time without blocking new requests by using I/O

eventing, callbacks and an event loop

•  … is ideal for I/O intensive tasks, but less for CPU intensive -  CPU intensive tasks within the application would block the process and must be offloaded in

worker threads/processes

EVENT PROCESSING WITH NODE.JS

In other words a perfect fit for IoT where the main task on the edges and in the fog is collecting sensor data

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NODE.JS EVENT LOOP

waiting waiting

Incoming request

Query DB (offloaded)

Process Result

Write log (offloaded)

Respond

Event Queue

Event Loop (Single Thread)

Thread Pool & Async IO

Filesystem

Network

Other

*http://kunkle.org/nodejs-explained-pres

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•  Naive example of a Node.js appication

NODE.JS CALLBACK HELL

callback 1

callback 2

callback 3

Confusing, this gives even wrong results!

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•  Also called futures, deffereds, eventuals,… •  A promise is an object (proxy) that represents the result of an asynchronous

function call

•  Biggest advantage of promises is that they can be chained to avoid callback hell

•  Promises can return any other value and the next 'onFulfilled' will be passed the value as argument

NODE.JS AND PROMISES

Promises are a simple form of Dataflow programming

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•  Traditionally a program is modeled as a series of operations happening in a specific order, in other words how to do computations

WHAT IS DATAFLOW?

Source: http://www.autobild.de/

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•  Dataflow programming emphasizes the movement of data and models programs as a series of connections. It describes what computation should be performed

WHAT IS DATAFLOW?

Source: http://commons.wikimedia.org/wiki/File:Hyundai_car_assembly_line.jpg

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•  Describes a graph of nodes, which exchange messages containing data via the edges.

•  The edges are defined outside the nodes, in others words nodes have no control on where the data comes from and where it goes to

FLOW BASED PROGRAMMING (FBP)

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•  Unix pipes are an example of linear flow based programming while a stream of data follows the pipes and the different 'smaller' dedictated applications run in parallel

FBP: UNIX PIPES

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FBP: YAHOO PIPES

Source: https://pipes.yahoo.com/pipes/pipe.info?_id=ZKJobpaj3BGZOew9G8evXg

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FBP: ENTERPRISE APPLICATION INTEGRATION

http://www.eaipatterns.com/Chapter1.html

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FBP: NODE-RED

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A NETWORK OF CONNECTED LIGHT-WEIGHT NODES TO PROCESS STREAM(S) OF EDGE GENERATED EVENTS VIA MESSAGE PASSING

•  According to the founders: -  A light-weight, edge of network, application builder -  Easy to use, drag and drop interface -  A tool that allows the developer to focus on the task at hand

FBP: NODE-RED

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•  Messages are JSON objects

FBP: NODE-RED

“payload : “Hello world!” “topic” : “foo” … …

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•  Different categories of nodes are defined:

-  Input: to process incoming events •  Example: Inject trigger, HTTP, TCP, UDP, websocket, MQTT, file, Datastore, social

(Twitter), … and custom nodes

-  Output: to serve or send outgoing events •  Example: Debug, HTTP, TCP, UDP, websocket, MQTT, file, Datastore, social (Twitter), …

and custom nodes

-  Functions: to manipulate messages and message payloads •  Transform, filter, map, analyse, …

FBP: NODE-RED

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•  Generic Function node: -  Runs user-defined javascript code in a sandbox -  Returns (forward) custom build messages with payloads

•  return msg;

•  return [msg1, msg2, msg3];

•  return [msg1, [msgA, msgB]];

FBP: NODE-RED – FUNCTION NODE

msg

msg1

msg2

msg3

msg1

[msgA,msgB]

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•  Each node has its own context to save state between calls -  Since node.js is single threaded, no race conditions can occur and the state is

always correct and up to date

FBP: NODE-RED – FUNCTION CONTEXT

count + 1

msg

countMessage

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•  Custom nodes are defined via a pair of files: -  .js :

•  defines what the node does

•  runs on the server

-  .html : •  defines the node's properties, edit dialog and help text

•  runs in a browser

•  When configuration needs to be shared between nodes, eg. IN node and the related OUT node share the same IP address, a special config node can be defined -  A dependeny on the config node is added in the custom node

FBP: NODE-RED – CUSTOM NODES

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•  What if

(FUNCTIONAL) REACTIVE PROGRAMMING (FRP)

meant C always equals A plus B, at any time?

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•  The functions in a cell/chart react on changes in another cell

FRP: SPREADSHEETS ARE REACTIVE

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•  In reactive programming, datatypes represent a value “over time”* -  For example getting mouse coördinates

in reactive programming, the assignment needs to be made only once and the variables/properties will always be up to date with the latest values

-  All following computations based on these variables will also be values that change over time

FRP: DYNAMIC VALUES

*http://stackoverflow.com/a/1028642

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FRP: BACON.JS – HOW DOES IT LOOK LIKE?

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FRP: BACON.JS – ‘C = A + B’, ALWAYS

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•  'Functional' means that building blocks of functional programming are used -  Ideas are borrowed from languages such as Haskell, Lisp, Scheme,...

•  Higher order functions are used extensively all over the place -  Higher order = takes one or more functions as input and/or outputs a function -  Examples:

•  Map, filter, scan, combine, takeWhile,...

•  See https://github.com/baconjs/bacon.js/ for an exhaustive list supported by bacon

•  See https://github.com/ReactiveX/RxJava/wiki/Observable for visual representation of many of these functions

FRP: ‘FUNCTIONAL’ REACTIVE PROGRAMMING

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•  Transform items emitted by a stream/property by applying a function to each of them

FRP: HIGHER ORDER FUNCTION map()

https://github.com/ReactiveX/RxJava/wiki/Transforming-Observables#map

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•  Filter items emitted by a stream

FRP: HIGHER ORDER FUNCTION filter()

https://github.com/ReactiveX/RxJava/wiki/Filtering-Observables#filter

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•  Apply a function to each item emitted by a stream and emit each successive value

FRP: HIGHER ORDER FUNCTION scan()

https://github.com/ReactiveX/RxJava/wiki/Transforming-Observables#scan

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•  Emit items emitted by a stream as long as a specified condition is true, then skip the remainder

FRP: HIGHER ORDER FUNCTION takeWhile()

https://github.com/ReactiveX/RxJava/wiki/Conditional-and-Boolean-Operators#takewhile-and-takewhilewithindex

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FRP: APPLYING FRP IN IOT – BACON.JS & TESSEL

https://github.com/BareMetalJS/tessel-baconjs-examples

DEMO?

Q&A KEEP IN TOUCH

(don’t forget, we are looking for partners for European Funding opportunities)

sven.beauprez@iotbe.org https://www.linkedin.com/in/svenbeauprez

@SvenBeauprez and @iot_bE