How to make a software developer happy ?

Leave your comfort zone

To be or not to be (happy), that’s the question. In this article, I expose some thoughts about what could make a software developer happy in his work. I wrote this article with several targeted audience in mind : Junior developers, Senior Techleads and H&R resources.

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Parallell issues with Java software : useful links to troubleshoot

Java 8 Threads/Promises/CompletableFuture/ForkNodePool

I am writing a new release of my Spring CQRS Module(link1, link2), including a parallel execution feature.

However I am encountering several issues with the Java 8 promises aka CompletableFutures.

My issues are :

  • I am using a dedicated ForkNodePool but some promises are stilled created outside my pool
  • Some threads are slow to die (WAITING state is too long)
  • Completable.allOf is creating promises in the common ForkNodePool
  • I had an exceeded waiting thread exception

Here is two links that are helping me a lot to solve these problems :

  • Java Parallel Calamity : link
  • The Java Fork/Join Framework : link2

These two articles are well documented and explain into the details how Java/Threads/Java/JVM/Promises and parallel streams works.


Java developer testing toolbox

JBehave : code

An article dealing with Java application and testing frameworks and related libraries. Continue Reading


How to implement CQRS with Spring : new framework

This article is a presentation of a new little framework, I have developed and used on several projects.

The framework is for Spring Framework and requires Java 8.0. The code is on GitHub and downloadable from Bintray or JCenter.

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TOP open-source dashboard solutions 2017

Dashboards can be a very efficient communication tool for a team, between managers and business units. It enables an organization around a vision to share common goals. It can also be useful to identify weaknesses in processes and adapt your strategy according to them.

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Test and Data Generation for Java Unit tests

Today I was preparing a presentation about Software Code quality for a TechTalk on Thursday. I made a search on Internet about Automatic Unit test generator and Data Generators. I will present some tools I have tried. Today, we will speak of Randoop.

Randoom Test Generator

Randoom Test Generator

The first tool name is Randoop.. This tool is existing since 2007 and its purpose is to generate automatically unit tests 🙂 Directly from your class definition!

To use it you have two choices:

  • You can use your software JAR or classpath directory.
  • You can include it in your test compile path (on gradle or maven) and creates a main or unit test.

To explain short the theory, thanks to the Java reflection it’s quite easy to produce automatic tests validating some contracts of your API.

Some examples: – toString() should never returns null or throws an Exception – equals() and compareTo() methods have a long list of constraints – Reflexivity: o.equals(o) == true – Symmetry: o1.equals(o2) == o2.equals(o1) – Transitivity: o1.equals(o2) && o2.equals(o3) ⇒ o1.equals(o3) – Equals to null: o.equals(null) == false – It does not throw an exception

Therefore this tool is generating unit tests with JUnit(TestSuite) for the list of classes you provide.

I have done some tests and you can reach 50-60% of coverage quite easily.

The main drawbacks of the solution are: – The unit tests are drawing a snapshot (precise picture) of your code and its behaviour however some tests are really non-sense and you don’t want to edit them. – They don’t replace handwritten tests since the tool is not understand the different between a String parameter emailand fullName. He will mostly use dumb strings.

About the technology, it’s not production ready: – I had troubles with the jar and its dependency plume. – The JAR is a fatjar and coming with dependencies that broke my software.

In conclusion, I will fork the software and try to fix the problems to make it more popular 🙂


Modularizing C/C+ Softwares

A presentation I made (in french) about how to modularize C/C++ Softwares and the various ways to implement it.

Here is the summary of the presentation.

Primary goals :

– How to scaffold a C/C++ Software ?
– What is the difference between a regular include directive and a system include directive ?
– Understand how the include directives works with CMake
– How to write appropriately a C/C++ header ?

Secondary goals :
– How to export symbol and definitions ?
– How to optimize dependencies between files
– How to generate precompiled headers
– Best practices to produce C/C++ modules

Here the full presentation:
[slideshare id=54013887&doc=rappelsmodularisationapplicationcc-151016091120-lva1-app6892]


My weekly DZone”s digest #1

This is my first post that offers a digest from a selection of DZone’s articles. I will pick DZone’s article based on my interests.

This week the subjects are : BDD Testing, Bad code, Database Connection Pooling, Kotlin, Enterprise Architecture

A few benefits you get by doing BDD

A few benefits you get by doing BDD : This article is an introduction to the Behaviour Driven Development practice. It’s interesting because we are regularly meeting teams, developers, architectures (pick your favorite one) that are confusing technical details and functionalities. As a result, the design, the tests and the architecture hides the user behaviour (the use cases ?) under a pile of technical stones. This article is a nice introduction. I recommend to go further these articles : * Your boss won’t appreciate tdd, try BDD * BDD Programming Frameworks * Java Framework JBehave.

Gumption Traps: Bad Code

Bad code, how my code...

Bad code, how my code…

Gumption Traps: Bad Code : an article about the bad code and how to deal with it.

{% blockquote Grzegorz Ziemoński%} The first step to avoid the bad code trap is to stop producing such code yourself. When faced with existing bad code,one must work smart to maintain motivation. {% endblockquote %}

This is a good introduction sentence. This week, I had a meeting with a skilled and amazing team. The meeting’s goal was to find a way to find the technical debt. The very technical debt that is ruining the application and undermining the team’s motivation. What I found interesting and refreshing in this article, is the pragmatic tone and the advice.

{% blockquote Grzegorz Ziemoński%} To avoid bad code, try to minimize the amount of newly produced bad code. {% endblockquote %}

How to avoid the depress linked to the bad code ? First of all, I want to say that developers are not receiving enough training on how to improve the code. Usually university / college courses are dedicated about How to use a framework. Therefore, few of them are able to qualify what is a bad code, what are its characteristics and de facto the ways to improve it. To avoid bad code, I try to demonstrate the personal benefits for the developers to improve their skills. Quality is not only a question of money (how much the customer is paying) but rather how much your company is paying attention to your training and personal development.

A lot of developers are overwhelmed under the technical debts without the appropriate tools (mind, technics, theory) to handle it. I try to give them gumptions about the benefits to be a better developer and how to handle the weakness of a sick application. To save a software rather than practicing euthanasia 🙂

Database Connection Pooling in Java With HikariCP

When we are discussing about Database connection pooling, most of my colleagues are relying on the good old Tomcat dbcp. However there is a niche, really funny and interesting, the guys that a competing for the best DBCP. And HikariCP is clearly a step ahead of everyone.

The article Database Connection Pooling in Java With HikariCP is presenting how to use a custom DBCP in your software.

Hikari Performance

Hikari Performance

I think it would have been great to present the differences with the standard DBCP and further debate on the advantages/disadvantages of the solutions. A good idea for a newt article 🙂

Concurrency: Java Futures and Kotlin Coroutines

Java Futures and Kotlin Coroutines An interesting article about how Java Futures and Kotlin co-routines can coexists. Honestly I am a little bit disappointed and thought that Kotlin would make things easier like in Node.JS

Are Code Rules Meant to Be Broken?

Another article about Code Quality and we could be dubious whether exists an answer to that question : Are Code Rules Meant to Be Broken.

I won’t enter too much in the details, the author’s point of view seems to be Code Rules are good if they are respected. If they are broken, it implies that the Code rules need to evolve 🙂 What do you think about it ?

Java vs. Kotlin: First Impressions Using Kotlin for a Commercial Android Project

This article is interesting since it presents a feedback session on using Kotlin in a Android project.

The following big PLUS to use Kotlin are :

  • Null safety through nullable and non-nullable types, safe calls, and safe casts.
  • Extension functions.
  • Higher-order functions / lambda expressions.
  • Data classes.
  • Immutability.
  • Coroutines (added on Kotlin 1.1).
  • Type aliases (added on Kotlin 1.1).

  Quality Code Is Loosely Coupled

Quality Code Is Loosely Coupled

This article is explaining one of the most dangerous side of coding : Coupling. Must to read article despite the lack of schemas.

Five Habits That Help Code Quality

This article is a great introduction on code assessment. These five habits are indeed things to track in your software code as a sign of decay and code sickness.

The habits are : – Write (Useful) Unit Tests – Keep Coupling to a Minimum – Be Mindful of the Principle of Least Astonishment – Minimize Cyclomatic Complexity – Get Names Right

10 Good Excuses for Not Reusing Enterprise Code

This article is really useful in the context of Digital Transformation to assess which softwares you should keep and throw.

Example of excuses : – I didn’t know that code existed. – I don’t know what that code does. – I don’t know how to use that code. – That code is not packaged in a reusable manner.

Test proven design

An interesting article and example on how to improve your own code using different skills. I really recommend to read this article and the next future ones : Test proven design.


I have tried Vue.js and I love it

Vue.js Framework

I have tried Vue.js and just love it.

Some weeks ago, I started a new project for which, I have to build an internet website.


After spending really long hours on internet, browsing, collecting every possible testimonials and advices and comparing them to my first impressions, I decided to start with an hybrid / multiple page site.

(if you are interested by the reasons, it will be the subject of another post).

An hybrid /multiple page site is a website where the content is rendered both from server side and client side at the opposition of single page application (SPA) full client side and a classical server side site(PHP..) Since I want to use the power of modern Js Frameworks as double binding, refreshing, Ajax widgets, Es2016, reactive programming and somewhat control which pages needs to be reloaded, I had to make a choice.

The list of choice is somewhat limited if keep only the 5 most popular ones. (yes I am resolutely not a pioneer of the JavaScript Jungle)

The framework selection

I made the following list :

  • Angular 2+ (they are increasing the major version number for each patch 😅)
  • React.js
  • AngularJS
  • Ember. Js
  • Vue.js
  • JQuery (it is a joke)

Selection criteria

I defined some selection criteria besides the popularity :

No code bloat : specifically to JavaScript, the syntax and the missing OOP native programming have been producing many frameworks with dumb syntax without any semantical and often syntaxical meaning. To overcome the limitations, many frameworks are using syntax sugar, making them a nightmare to memorize. The most ridiculous is the attempt to stick on these syntaxical blobs, some pseudo theorical terms.

A good framework should offer different levels of usages from the straightforward approach to build quickly and easily a website with the common use cases to the low-level approach where the experimented developer is able to tune the required details. What has been done in Laravel, Spring framework or Symphony are good samples.

Symphony framework is known as a huge galaxy. Many components, industry quality grade, but an overwhelming complexity if you start head on.

Therefore they have created a micro — framework called Silex to bootstrap an PHP application without the nasty details and it is deadly simple. If you want more complex things, the components behind Silex are the Symphony ones.

For a web framework, always study how do they handle forms. Especially a basic post form. It takes five minutes in plain HTML to build an (unsecured) form. How long does it take with this framework?

The same thing works for **Spring* and Spring boot.

The framework must have a business friendly licence. No doubt, no legal restriction for the future company. (by the way do you know you cannot build weapons software in Java, please stick to the line…)

An extensible / plug-ins architecture. I believe the success of a framework resides in the possibility to enable the necessary functionalities (aka feature toggling) during your project. Authentication, reactive programming, lazy loading, modularity.

The evaluation (aka trolling section)

Based on these selection criteria, here is my evaluation.

Disclaimer: I have a highly respect for the guys who wrote these frameworks and I do not doubt of their outstanding skills. AngularJS

I have experienced projects with AngularJS and I renounced since it is a deprecated technology. Too much code bloat, slow (I should rather say hard-to-tune) and all efforts are concentrated on the new Angular framework. Also, I think I could have a problem with my use case and disabling the AngularJS router.

Angular 2

Angular 2: I have received a training in January and wrote several prototypes since. I have been a huge fan of typescript, angular-cli. I was happy and thinking, they took the best ideas from the other frameworks and build a big melting pot.

Angular : melting pot

In Angular, you will find web components, uses template a la React.js, you have opt-in double binding, directives, modular architecture, lazy loading and so on and so on. But I progressively hate Angular for many details, slowing me down in my developments.

I really dislike their API and concepts to build forms. You have two choices, a template form design and programmatic form design. The first one is almost useless and the second one is deadly cumbersome.

In Angular, they decided to kill HTML and recreate it. How? Case-sensitive attributes and non HTML attributes. You cannot use your normal code editor on it. Beautifier tools not works or partially works. And worse of all, they conceive this awful syntax based on brackets, parens, Well, I think their are huge practitioners of the Brainfuck language.

Brainfuck language

Brainfuck language

The last issue I encountered is with their wish to produce an industrial, scalable (in the sense if I put more developers on my project, I maintain a stable learning and complexity curve). Yes, they provide dependency injection, IOC. But it really increases the learning curve.


I really wanted to start with React.js. As far I have studied it, the framework seems full of promises, with some nice pluggable functionalities.

However at the time I began to use it, I received a lot of news. The concern is about the React.js license, the Facebook license (link1, link2, link3).

Since there is a threat for the future business (everything can be considered as a social network after all), I have rejected it.


I have never tried Ember.js. Based in my readings, the framework is definitely worth of attention to build SPA applications but not for my use case. Note : during the writing of this post, I felt on that link, confirming that maybe I was wrong about ember.js


On Twitter, I am receiving a lot of feedback from happy users of Vue.js and I decided to give a try.

The syntax seems deadly simple.

Here is the brief of my experience :

I did not use vue-cli, I had to create my own packaging to adapt Vue.js to multipage architecture.

Code bloat: the Vue.js framework is really simple and the documentation quite good. The documentation for the plug-in vue-loader is quite good but I really hate the webpack syntax to enable it (rant..)

Learning curve: I did not try the most hard-core functionalities of Vue.js, though I am using vue-loader, a different template renderer (pug), transitions, a little bit components and lazy loading.

My biggest difficulty have been to maintain my js bundle as low as possible by producing chunks.

The second issue has been to understand why creating a view was creating an App and my component below using the render() function. However I think that Vue.js is easier than Angular. 2.

As in the previous example, the syntax is quite straightforward, no need to learn complex concepts to begin with.

The framework is also compatible with Typescript and the logic behind is quite simple.

Vue.js can be extended with several plug-ins and functionalities. I did not try all of them and the fact you are enabling them manually is comforting me in my approach.

Vue.js is not enforcing a particular programming paradigm(IOC, interfaces, Reactive programming, or. RxJS).

The only reproach I could formulate is a little fear about the Vue.js ecosystem. Please integrate existing libraries rather trying to recreate or mimic ReactJS libraries.

In conclusion, both of these frameworks are legitimate and have their lot of practitioners, and I don’t blame it. Vue.js has been my choice and I do not regret it, yet, since it has made my project easy, fun and effective.

I will try to provide more feedback in the following weeks especially on form editing, unkt testing and E2E testing.

Thanks for your attention


How I switched my blog from OVH to Google Container Engine

In this short story, I will relate how I migrate my blog personal website from a classic VM instance to Google cloud using Kubernetes, Docker, Nginx.

Onoe of my personal goal was also to have a cloud deployed website without spending any money.


Long story made short, I have been using Docker on several projects since one year. I progressively got accustomed with the ease of deployment provided by Docker. The issue ? The day I have launched my blog (on February 2017),for time and cost reasons, I picked an VPS instance from OVH.

Why OVH ? Clearly it is one of the cheapest IAAS provider and quite popular there in France. I have been using it for several projects without any major issues.

OVH has an offer of public cloud OVH Public cloud. However the offer looked immature at that time both in documentation than on reviews. The second reason of my rejection is about cloud adotpion. A lot of experts are turned toward GCloud and AWS. Spending my efforts on OVH would not provide enough visibility at short term, in my job.

To better accompany my colleagues and customers to adopt the cloud , I have decided to eat my own dog food. And among my personal projects, I have decided to migrate first my blog.

And to switch my blog from OVH to Google Cloud (Container Engine).


Here are some interesting articles about pricing and functionalities for the major cloud providers :

Technical situation

My blog is hosted on a VPS server (shared instance on OVH). I have installed on it, Apache 2, some monitoring and security system and Let’s encrypt to obtain a free SSL certificate.

Hexo command line

Hexo command line

My blog is not using the classifical wordpress, I am quite fond of static website generators and more recently of flat/headless CMS.

I am using HexoJS as a CMS. Main features are you are writing your article in Markdown and the blog has to be regenerated to produce the static files, producing quite optimized pages.

Hexo command line

Hexo command line

How to switch from a legacy deployment to the cloud.

These are the explanations how I proceed to migrate this website.

 A) Create my Google Cloud Account

Yes, we have to start from the beginning and I created a new Google Cloud Account. Though it is rather easy to create its account, I have been surprised. It was impossible to for me to pick an individual account.

It’s even in the Google FAQ (FAQ).

{% blockquote By Google FAQ %} I’m located in Europe and would like to try out Google Cloud Platform. Why can’t I select an Individual account when registering? {% endblockquote %}

The reason (thanks EU.. ) is dumb as fuck : In the European Union, Google Cloud Platform services can be used for business purposes only

For information, in Switzerland, the limit is lifted.

Interesting enough, the free trial on Google Cloud has been expanded to 300$ for one year.

B) Discover Google Cloud

Well the UI is easy to manipulate even with this nagging collapsing menu on the right side.

Google Cloud Console

Google Cloud Console

The documentation is quite abundant but I found two major issues :

  • Lack of pictures and schema : most concepts are described with a bunch of words. Fortunately, some very kind people made great presentations (here and here).
  • Copy/Paste from the Kubernetes website : yeah most of the documentation can be found on Kubernetes, logically.
  • Lack of informations and use cases : for some examples as using this damn Ingress. Why people are not providing Gist 🙂

I created a cluster with two VM instances, 0.6GB of RAM and 1 core. Indeed I wanted to play with the load balancing features of Kubernetes.

Create a cluster

Create a cluster

C) Replicate my server configuration as a Docker container

The easiest and funniest part has been to reproduce my server configuration with Docker and to include an evolution. I wanted to switch from Apache 2 to Nginx.

First solution I created. I used a ready-made (and optimized) container image for Nginx and modified my build script to generate the Docker image. The generated website is already integrated into the Docker image.

FROM bringnow/nginx-letsencrypt:latest

RUN mkdir -p /data/nginx/cache
COPY docker/nginx/nginx.conf /etc/nginx/nginx.conf
COPY docker/letsencrypt /etc/letsencrypt
COPY docker/nginx/dhparam /etc/nginx/dhparam
COPY public /etc/nginx/html

I made several tests using the command docker run to check the configuration on my own machine.

docker run --rm -i -t us.gcr.io/sylvainleroy-blog/blog:latest -name nginx

D) How to host my Docker image ?

My second question has been how to store my Docker container ?

Creating my own registry ? Using a Cloud Registry ?

I have used two different container registries in my tests.

First is the Docker Hub.

Docker Hub

Docker Hub

What I appreciate the most with the Docker Hub, is that I can delegate the creation of my Docker images to the Hub by triggering a build from GitHub. The mechanism is quite simple to enable and really convenient. Each modification of my DockerFile is triggering a build to create automatically my Docker image!

Here is a small draw to explain it :

Docker Hub & Builds draw

Docker Hub & Builds draw

And some part of the configuration.

Docker Builds Configuration

However Google Cloud is also offering a container engine and its usage has been redundant. I kept it to use it with CircleCI.

Therefore for the time being, I am storing my Docker container on Google Cloud.

Google Cloud Container Registry

Google Cloud Container Registry

With this kind of command :

gcloud docker -- push us.gcr.io/sylvainleroy-blog/blog:0.1

E) The Cloud migration in itself

Maybe it is one my fancy side, but I have only used the GCloud CLI to perform the operations.

Install Google SDK

Everything go smoothly but don’t forget to install Kubernetes CLI.

gcloud components install kubectl

I had a problem with the CLI. It could not see my new projects (only some part of them) and I had to auth again.

gcloud auth login

And perform a new login to see the update.

Don’t forget to also add your cluster credentials using the GUI instructions (button connect near each cluster).

Google Cluster

Google Cluster

gcloud container clusters get-credentials --zone us-central1-a blog

 Understanding the concepts of Pod, deployment

It took me time to understand what is a deployment and a pod. Using docker and docker-compose I could not attach the concepts.

That is one of my concerns with Kubernetes, some technical terms are poor and does not really help to understand what is behind.

Well, I finally create a deployment, to create two docker instances inside my pod (replica=2). This deployment file is declaring basically that it requires my previous Docker imamge and that I want two copies. The selector and the label mechanism is quite handy.

apiVersion: extensions/v1beta1
kind: Deployment
  name: blog-deployment
  replicas: 3
        app: nginx
        role: master
        tier: frontend
      - name: nginx
        image: us.gcr.io/blog/blog:0.9
          - containerPort: 80
            name: http
          - containerPort: 443
            name: https 

I use such commands to create it :

Ì€kubectl create -f pod-blog.yml

KubeCtl Pod informations

KubeCtl Pod informations

 Automating the generation, docker image building and deployment

I have automated the full cycle of my site generation, docker building and container registry and pod reload using CircleCI.

CircleCI Deployment Schema

CircleCI Deployment Schema

And the good thing is that all these things are free.


After playing during two weeks with it on my spare time, I have the following feedback :

 Rolling Update

The deployment mechanism and how the rolling update is performed are impressive and a time-saver.. Some banks are still using an manual way or semi-automated way like Ansible to deploy their software and the rolling updates are performed awkwardly. Here Kubernetes is deploying on the background the new version, controlling its state (roughly) and if the conditions are met, switching from the old version to the new version. I am using this mechanism to bench my Docker new images and push the new versions.

 Load Balancing mess

I had to struggle a lot to set up my load balancer. Well, not at begin. Kubernetes and GCloud are describing precisely how to set-up a Level-4 LoadBalancer. It takes few lines of YAML and it was fine. However, I had huge difficulties when I decided to switch to TLS and my HTTPS Connection with Let’s encrypt.

I met several difficulties :

  • How to register my SSL certificate on a Docker container tough not deployed ?
  • What the fuck is a NodePort ? The difference with ClusterIP and a LoadBalancer and an Ingress ?


  • Where should I store my certificate ? in the GCloud configuration or in my NGINX ?
  • Why Ingress is not working with multiple routes ?

To address the following issues, I found the temporary solutions :

  • I am using Certbot/Let’s Encrypt certification using DNS. That way, I can generate my certificates "offline".
  • I am not sure about the definition of what is a NodePort, either I need a LoadBalancer for a single container in my pod or simply open the firewall. These concepts, introduced with Kubernetes are still obscure for me, even after several reading.
  • I took the decision to implement my HTTPS LoadBalancing by modifying my NGINX configuration to store the certificate and rely on a Level 4 LoadBalancer to dispatch the flow.
  • I tried really hard to make Ingress working (the level-7 LB) but even the examples where not working for me (impossible to map the port number 0 error) and really bad documented.

 Persistent volume

The documentation about persistent volumes is not precise in Kubernetes and GCLoud and have important differences between the implementation and Google and even between versions.

You have many possibilities :

  • Use a Persistent Volume, PersistentClaim and attach them to your containers
  • Generating directly a volume from your deployment file

Another issue I have met, my docker container was failing (and the pod itself) because the persistent volume created is never formated.

But why ????

Indeed in your deployment file, you have properties to set the required partition format. But no formating will be performed.

And therefore I had the following next issues :

  • How to mount something unformated ?
  • How to mount something unformated in a container of the pod without using the deployment ?
  • Why is there so few documentation in Google Container Engine (in comparison with Google Compute Engine) ?

The recommended solution is to create an VM instance by HAND using Google Compute Engine, to mount attach the disk to the instance. To mount it manually and trigger the formatting. WTF

If you have a better way to handle the issue, I am really interested!


After a month of deployment, I haven’t spend a buck. My page response time decreased from 3.4s to 2.56s And I am not waking up during the night, the eyes full of horror thinking about how to reinstall the site. I only have a container to push.

I am not using yet the Kubernetes UI and I don’t see yet the necessity. The CLI offers almost everything.

Cleaning a cluster, the pods and deployments requires several steps and maybe could be simplified.


One very important aspect of my project was also to decrease the bill to host the site.

Currently, here is my bill for 1600 visits per month :

  • I have a GitHub private repository (~7$/month)
  • I am using the free tier of CircleCI offering me the usage of a Private GITHub repository and important number of build
  • Docker Hub is free for any number of public repositories and 1 private docker repository.
  • I am using the free tier of Google and I spent 1$ in one month and the bill is shared between my blog and my other projects.
  • I have a cluster of 2 VM for my blog

Compared to my 79€/year for my VPS.

Interesting links