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.

Displaying memory statistics along with hostname and war files

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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

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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

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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

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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.

Maven: Installing / adding local jar into your local maven repository

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I needed to install a local jar file into my laptop’s local maven repository and found this article. I used this approach to install this jar file in my repo:

mvn install:install-file -Dfile=my-model-1.2.1.jar -DgroupId=com.cyberaka.my.package -DartifactId=my-model -Dversion=1.2.1 -Dpackaging=jar -DgeneratePom=true

This duly added the local jar file under appropriate group id and artifact id inside my maven repository and I was able to refer to this dependency through my project’s pom.

 

Using NGINX for Proxy Pass

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Lets say I have two servers running on my laptop
1. http://localhost:3000 – This is the UI
2. http://localhost:4000 – This is the web services API

So now I need to setup something like this:
1. http://localhost/ – This should point to UI
2. http://localhost/api/ – This should point to web services API

To set this up I have used NGINX and added this section in the “server” section of the nginx.conf file. On my Mac system this file is located at: /usr/local/etc/nginx/nginx.conf

location /api/ {
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass http://localhost:4000/;
}

location / {
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass http://localhost:3000/;
}

To reload NGINX I use the “-s reload” parameter for nginx. On my Mac I execute this command:
/usr/local/Cellar/nginx/1.10.0/bin/nginx -s reload