Wednesday, March 11, 2015

DevNexus Docker for Java Developers: Hands-On Lab

Hello DevNexus 2015
March 12 2015 at 1:00 PM

We have 75 minutes to get your laptop setup with Docker for building and running Java EE applications.   The good news is that you can come to the session prepared.   I made the assumption that most folks will have a Windows or Mac OSX laptop and can use boot2docker which bundles VirtualBox.

The complete tutorial (the core of the overall talk) is available on Github

If you can, make the attempt at getting boot2docker running on your Windows or Mac laptop prior to the session.  There can be numerous challenges with the installation process, most of which I have tried to describe workarounds in the tutorial document.   Once you have successfully executed:

docker run centos /bin/echo "Hello World"

You are ready to go!

You can also simply install Docker on your Linux machine directly:

Saturday, March 7, 2015

Publish Subscribe with Spark Core (1+1=3)

Do not make the same mistake that I made.  I purchased a solitary Spark Core and nearly missed the awesomeness of Spark.   You must buy two (2) from, Sparks need friend!

A few years ago, I spent many hours with Arduino Uno but did not find it to be that engaging.   By default an Arduino Uno lacks networking and it is not a member of the "Internet of Things" unless you add on an appropriate shield or integrate another component.  At the time, the ethernet shield was somewhat expensive and Wifi fairly challenging.  Fast forward to 2015 and the world has changed dramatically.

I started exploring the Spark Core, the Open Source IoT Toolkit, essentially a Wifi-enabled Arduino for $39 (I have two Photons on backorder and backed the Electron on Kickstarter),  just last weekend.  This included my dusting off my Arduino Uno for testing various resistors, sensors, actuators, logic, etc prior to trying those so things on the Spark.  By this weekend, I wanted to see what it would take to "integrate" a couple of Spark Cores.

The Spark Core is inherently network-aware, in its default state, you must have a Wifi connection even to flash/program it (which does mean it is slower to flash than a USB-connected Arduino).  More importantly, your code can expose variables or functions which can be invoked via a REST API call to the Spark Cloud.  You can use curl to interact with the physical world - for a Java/JavaScript coder like myself...this is pretty incredible.

In addition, you can engage in publish/subscribe messaging between two or more Spark devices.

My thinking is that an intelligent sensor (based on Spark Core) in one location can take readings and based on need (e.g. stock needs replenishing,  conveyor motor offline, temperature is rising), can alert other intelligent actuators to take some action in the physical world.

In this case, I used a Force Sensitive Resistor where its reported value rises based on the amount of pressure (squeeze) you apply and I used the super simple Spark.publish API to send out the event to the Internet.   On the other Spark Core, I set up a subscriber that invokes a simple function to "animate" the servo+gripper also from SparkFun.   Both Spark Cores are sitting on their respective breadboards (the Core ships with a breadboard) and the subscriber core (the gripper) is being powered by the Spark Battery Shield.

Publisher (with Force Sensitive Resistor) Code

#include "application.h"

From the article:

int FSR_Pin = A0; //analog pin 0
int ledPin = 7;
bool wasHigh = false;

void setup(){
  pinMode(ledPin, OUTPUT);

void loop(){
  int fsrReading = analogRead(FSR_Pin);


  if (fsrReading > 3000) {

    if (!wasHigh) {
      Serial.println("sending HIGH");
      wasHigh = true;
      digitalWrite(ledPin, HIGH);
      Spark.publish("burrsqueeze", "HIGH", 60, PRIVATE);
  } else {

    if (wasHigh) { // the state is normally sub-3000
      Serial.println("sending LOW");
      digitalWrite(ledPin, LOW);
      Spark.publish("burrsqueeze", "LOW", 60, PRIVATE);
      wasHigh = false;

  delay(400); //just here to slow down the output for easier reading

Subscriber (with Servo+Gripper)

#include "application.h"

 Receives a 'squeeze' HIGH event and closes the servo+gripper to close

Servo myservo;

const bool DEBUG=true;

int minPos = 32;
int pos = 0;
int maxPos = 160;
int ledPin = 7;

int i = 0;

void close_gripper() {
  if (DEBUG) Serial.println("close");

  // close
  for(pos = maxPos; pos >= minPos; pos-=1) {

void open_gripper() {
  if (DEBUG) Serial.println("close");

  // open
  for(pos = minPos; pos < maxPos; pos += 1) {

void eventHandler(const char *event, const char *data)
  if (DEBUG) Serial.print(event);
  if (DEBUG) Serial.print(", data: ");
  if (data) {
    if (DEBUG) Serial.println(data);
    // assume LOW unless HIGH arrives
    if (String(data) == "HIGH") {
      digitalWrite(ledPin, HIGH);
    } else {
      digitalWrite(ledPin, LOW);
  else {


void setup() {
  if (DEBUG) Serial.begin(9600);
  Spark.subscribe("burrsqueeze", eventHandler, MY_DEVICES);
  pinMode(ledPin, OUTPUT);

void loop() {
  if (DEBUG) {
    Serial.print("I'm Alive: ");

Note: I use the Spark Dev (on desktop Atom-based Spark tool) so I include application.h

Monday, February 16, 2015

docker, Docker, DOCKER!

My first run of the Docker Tutorial Live has been canceled for today, February 16 at TriJUG, alas, Old Man Winter has intervened and we are expecting snow & freezing rain during the TriJUG meeting time window.  And for those of you who have lived in the South, snowflakes are a cause for major alarm - I suspect the grocery stores have already been raided for bread, milk, eggs and ammunition :-)

The next live event will be DevNexus in Atlanta on March 10 to 12th 2015.   DevNexus is an excellent JUG-organized developer-focused event which basically equates to a great speaker line-up at a great price point.  

For those of you following along at home (not physically making it to TriJUG or DevNexus), please check out the written Docker Tutorial materials - the focus is on the Windows-based enterprise Java Developer.  With our JBoss Tools project, we receive opt-in usage data that shows us that the vast majority of enterprise Java developers run Windows as their primary desktop.  While Docker is a Linux innovation, it can be run on Windows via boot2docker (which includes VirtualBox in its installation).  And Java developers do want to understand how building Docker images and running containers could impact their future toolchain and workflow.

I wrote the tutorial documents in markdown (many thanks to Pete Muir for helping my formatting) and stored them in github to make them "forkable" - hopefully allowing anyone who wishes to run their own Docker Workshop use the materials and perhaps even send back a pull request.

Getting Started with Docker, boot2docker, on Windows for the Java Developer

Adding MySQL and additional tips for Java EE on Docker

Once you have a comfort level with Docker builds and runs...then it is time to learn one of the orchestration solutions - basically tools that allow you to start multiple docker containers, linking them, declaratively.  We (Red Hat) are focused on Kubernetes by Google as that piece of the infrastructure.  Check out this short recorded demo of Kubernetes in action.