Author Archives: cyberaka

About cyberaka

I am an experienced Senior Solution Architect with proven history of designing robust and highly available Java based solutions. I am skilled in architecting designing and developing scalable, highly available, fault tolerant and concurrent systems which can serve high volume traffic. I have hands on experience in designing RESTful MicroServices architecture using Spring Boot, Spring Cloud, MongoDB, Java 8, Redis and Kafka. I like TDD (JUnit), BDD (Cucumber) and DDD based development as required for my projects. I have used AWS primarily for cloud based deployment and I like developing cloud enabled POC as a hobby in my spare time. I have deigned and developed CI/CD pipeline using Jenkins and leveraged Docker, Kubernetes for containerizing and deploying some of my applications. I am highly experienced in creating high performing technical teams from scratch. As an ex-entrepreneur I am very much involved in the business side of the IT industry. I love interacting with clients to understand their requirements and get the job done.

Java Code To Extract Email From Text

Leave a reply

I found a good piece of code which can be used to extract multiple email from a String. A modified version of the code is listed below:

public static String readContactEmailFromString(String resumeText) {
    final String RE_MAIL = "([\\w\\-]([\\.\\w])+[\\w]+@([\\w\\-]+\\.)+[A-Za-z]{2,4})";
    Pattern p = Pattern.compile(RE_MAIL);
    Matcher m = p.matcher(resumeText);

    StringBuilder sb = new StringBuilder();
    while(m.find()) {
        if (sb.toString().contains(m.group(1))) continue;
        if (sb.toString().isEmpty()) {
            sb.append(m.group(1));
        } else {
            sb.append("; " + m.group(1));
        }
    }
    return sb.toString();
}

Fetching colleague’s fork on Github

Leave a reply

I am currently using Github and all project members have forked the main repository into private repository. Now the problem is that I need to review my colleagues code committed in his branch inside his forked repository. So to do this I found out a good article that showed me exactly how to do that. I used the following approach.

git remote add my-colleague https://github.xyz.com/my-colleague/project.git

git fetch my-colleague

git checkout -b my-colleague-branch --track my-colleague/branch

After I do this I can see all the work done by my colleague and I can switch back to my branch anytime.

Spring Certification

Leave a reply

We can now do Spring certification without going for Pivotal training. It was long due and here it is finally!

Can you take Spring certification without Pivotal Training Course?

Read more: http://javarevisited.blogspot.com/2017/05/can-you-take-spring-certification-without-training-course.html#ixzz4hVUNb9fW

5 Spring Framework Books for Java developers (Includes Spring Security and Spring Boot) – Best of lot

Read more: http://www.java67.com/2016/12/5-spring-framework-books-for-java-programmers.html#ixzz4hVU7visy

List of good Curl commands

Leave a reply

I use CURL for debugging my REST endpoints every now and then if I don’t want to use Postman or DHC clients. I usually like to copy paste results / statistics from command line into emails to my colleagues. This gives them a plain jane command which they can use to test themselves as well as compare their results with mine. The following article has some good pointers on how to use CURL and some very practical examples have been provided.

15 Practical Linux cURL Command Examples (cURL Download Examples)

Displaying memory statistics along with hostname and war files

Leave a reply

I recently got into a situation where I had to debug around 10 servers all of which were suffering from memory issues. My java applications were slowing down after a day or so. Although its is difficult to diagnose this kind of issues which span across multiple VMs (welcome to Micro Services!) but with some little bit of scripting it is possible to see in real time the actual numbers if you manage to use tmux to multiplex multiple shell sessions stacked together. I hacked up the following command to display hostname, running war files as well as the memory statistics refreshed every 1 second on screen.

watch -d -n 1 "hostname | tr '\r\n' ' ' && printf \" \" && jps -l | grep .war | tr '\r\n' ' ' && echo "" && free -h"

Linux Disk Usage

Leave a reply

I found a good link which lists good usages of the Linux command “du”.

This command allows me to see the usage in a ascending sort which is really helpful.

Tested on Linux.
du -h / | sort -h

Tested on Mac OS.
du -hs * | gsort -h

In case you don’t have gsort install coreutils.
brew install coreutils

This variation allows me to see any line which has the text “G” in it which basically allows me to see folders using space in GBs. Agreed it might give some folder names as well with “G” in it but I can bear with it.

Tested on Linux.
du -h /the/path | sort -h | grep "G"

Tested on Mac OS.
du -h /the/path | gsort -h | grep "G" 

Setting up Sonarqube docker instance

Leave a reply

In order to setup a fully functional Sonarqube server via docker I use the following consolidated command:


docker run \
--detach \
--name=sonarqube \
--publish 9000:9000 \
--publish 9092:9092 \
--env="SONARQUBE_JDBC_USERNAME=sonar" \
--env="SONARQUBE_JDBC_PASSWORD=sonar" \
--env="SONARQUBE_JDBC_URL=jdbc:mysql://mysql:3306/sonar?useUnicode=true&characterEncoding=utf8&rewriteBatchedStatements=true" \
--link mysql:mysql \
sonarqube:5.1

This connects my dockerized mysql instance with sonar and it is able to create tables and start using MySQL properly for storing all it’s data.

Setting up MySQL docker instance

Leave a reply

In order to setup a fully functional MySQL server via docker I use the following consolidated command:

docker run \
--detach \
--name=mysql \
--env="MYSQL_ROOT_PASSWORD=abcd1234" \
--publish 6603:3306 \
--volume=~/Docker/mysql/conf.d:/etc/mysql/conf.d \
--volume=~/Docker/mysql/mysql-datadir:/var/lib/mysql \
mysql

The advantage of the above approach is that the configuration files can be defined under ~/Docker/mysql/conf.d folder on my system and it will be picked up whenever I bootup this instance. The second thing is that all information written by this instance will be stored outside of VM in the path ~/Docker/mysql/mysql-datadir on my system. So In case this VM goes away due to some unexplained reasons I can still bootup another docker instance of MySQL and point it to this data directory.