• A great leader isn’t one who holds a candle up for others, but helps them light their candles instead.

• Be decisive: realize that sometimes it’s not that the best decision is made but that a decision is made timely.

• Positive reinforcement, notice and recognize achievements and improvements, no matter how small, people work harder for people that notice their successes and work just enough for people who only notice their failures.

• Be the worker you want others to be, lead by example. Volunteer yourself to do projects.

• IMPORTANT: Don’t fear being wrong, say you were and move on. Don’t let people think that you shift blame to others or are incapable of recognizing your own failures.

• Be honest to those below you (in terms of feedback) and open about the reasons behind your decisions, you have to admit your mistakes as well..

• Be a buffer for them, from your boss.

• It’s about getting your team to work together, not about goals and targets. (Though you should have them.) Make time to listen to them.

• Ask for help & advice, hopefully you’re not the only one. If you are having trouble reach out, people will respect you for it, do not think less of you, you may inspire them to do the same.

• Be accountable to those below you.

• Be human. Your team will feel more comfortable asking for help and letting you know when things go wrong.

• Empathy is a good leadership quality

Before diving in deep, You should know what is Mosquitto:

Eclipse Mosquitto is an open source message broker that implements the MQTT protocol. The MQTT protocol provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it suitable for Internet of Things messaging such as with low power sensors or mobile devices such as phones, embedded computers or microcontrollers -- Wikipedia

Following is the docker-compose.yml I used to setup Mosquitto:

version: "3"
services:
    mosquitto:
        container_name: mqtt
        image: eclipse-mosquitto
        ports:
            - 1883:1883
        volumes:
            - "./mosquitto/config/broker.conf:/mosquitto/config/mosquitto.conf"
            - "./mosquitto/config/password.passwd:/mosquitto/config/mosquitto.passwd"
            - "./mosquitto/data:/mosquitto/data"
        networks:
            - app-network
networks:
    app-network:
        driver: bridge
}

Here is some explanation:

I gave my container a user-friendly name : “mqtt” so that I can access it and run some commands

container_name: mqtt

“eclipse-mosquitto” is the official image mentioned on their website. I used the latest image, thats why did not mentioned any version.

image: eclipse-mosquitto

“1883” is default port used by Mosquitto to enqueue/dequeue messages in broker. Since we are running in container, We need to also expose the port to host machine.

ports:
    - 1883:1883

Three directories, I used as volume to preconfigure the setup.

volumes:
    - "./mosquitto/config/broker.conf:/mosquitto/config/mosquitto.conf"
    - "./mosquitto/config/password.passwd:/mosquitto/config/mosquitto.passwd"
    - "./mosquitto/data:/mosquitto/data"

• To pass the configuration file
• To pass the list of users with their credentials.
• Since containers are volatile, Everything will be lost if container restarted. To make data persist, I mounted directory to keep the data on host machine.

Configuration file:

listener 1883
password_file /mosquitto/config/mosquitto.passwd
allow_anonymous false

persistence true
persistence_location /mosquitto/data
autosave_interval 10s
max_queued_messages 100

Dockerization

To up the container, you can run following command in command line or terminal:

docker-compose up -d

To start interactive session, run following command:

docker exec -it mqtt /bin/sh

Note: Image does not support “bash” alias

Security measurement:

I disabled anonymous usage in configuration file by changing allow_anonymous to false and provided the location of password file by password_file.

After starting the container, You need to add a user with password so that pub/sub can connect with your broker. Since, directory was mounted added user will presist even after restarting the container. Use

mosquitto_passwd -c password username

to store passwords in file. For example, command

mosquitto_passwd -c golang golang

will write following content in password file.

golang:$7$101$ccJ/dnmr0jLqzO6B$V4Y36vs2XlMFRsCe7zyLJdDeL1s++YSCm7ZbR1cVCA592o0td3hZrQ91J5w0cFSiM/3oBHnnT9gUO5xYSSheMQ==

End to End connectivity:

Installation of Mosquitto comes with some utilities to check end to end connectivity. These utilities will be accessable after starting up the docker container successfully.

Mosquitto Producer: This utility helps to enqueue messages in plain text. After opening the interactive bash session in mqtt container, You can run following command to enqueue the message:

mosquitto_pub -h localhost -p 1883 -u golang -P golang -t my-mqtt-topic -m "Test Message"

Mosquitto Subscriber: This utility helps to dequeue messages in plain text. After opening the interactive bash session in mqtt container, You can run following command to dequeue the message:

mosquitto_sub -h localhost -p 1883 -u golang -P golang -t my-mqtt-topic

Note: Make sure that credentials you set through password utility are correct.

Conclusion: I hope this post gave you a useful overview of getting an MQTT Mosquitto Broker up and running using Docker.

He had become a religious man, also called a Brahman, and was traveling from town to town to share his message. He was becoming so popular that when people heard the Buddha was coming they went to hear him speak. As a result many other Brahmans lost their audience.

One Brahman was so upset with the Buddha that he found him and went to see him late at night. He was furious! “You have no right teaching others,” he shouted. “You are as stupid as everyone else. You are nothing but a fake!” Buddha smiled at the Brahman and listened until he was done with his rant. When the Brahman was done, Buddha still sat, smiling at him. This made the Brahman even angrier. “Why are you just sitting there smiling? What do you have to say?”

Then Buddha spoke. “Tell me something, Brahman: Do friends and colleagues, relatives and kinsmen, ever come to your house as guests?” “Yes,” the Brahman answered. “And tell me something, Brahman,” Buddha continued. “Do you serve them foods and delicacies when they arrive?” “Yes,” the Brahman answered, “I do.”

“And tell me something, Brahman,” Buddha continued. “If they don’t accept them, to whom do those foods belong?” “Well, I suppose if they don’t accept them, those foods are all mine.” “Yes,” said Buddha. “In the same way, Brahman, I do not accept your anger and your criticism. It is all yours.” The Brahman was stunned and could think of nothing to say. His anger continued to bubble up inside him, but he had nowhere to put it. Nobody was accepting it or taking it from him. Buddha continued: “That with which you have insulted me, who is not insulting, that with which you have taunted me, who is not taunting, that with which you have berated me, who is not berating, that I don’t accept from you. It’s all yours, Brahman. It’s all yours.

“If you become angry with me and I do not get insulted, then the anger falls back on you. You are then the only one who becomes unhappy. All you have done is hurt yourself. If you want to stop hurting yourself, you must get rid of your anger and become loving instead. “Whoever returns insult to one who is insulting, returns taunts to one who is taunting, returns a berating to one who is berating, is eating together, sharing company, with that person. But I am neither eating together nor sharing your company, Brahman. It’s all yours. It’s all yours.”

Reference:

Pasricha, Neil. The Happiness Equation: Want Nothing + Do Anything = Have Everything (p. 61). Penguin Publishing Group.

What is Modulo Operator:

In computing, the modulo operation finds the remainder after division of one number (dividend) by another (divisor) -- Wikipedia

One common use case for this operator is to check if a number is even or odd. If remainder of a number is Zero when 2 divide it then it is an Even number else it is Odd.

0 % 2 = 0
1 % 2 = 1
2 % 2 = 0
3 % 2 = 1
4 % 2 = 0
5 % 2 = 1

The result of modulo operator can never be greater than divisor, it will always be one lesser then second number. The reason this happens is because division is all about fair sharing.

How to avoid Modulo operator:

I modern architecture, Division operator may take several clock cycles to perform its operation. Modulo operators can be easily translated into Bitwise operators. If a divisor is power of 2 then it can be replaced by bitwise AND operator. It will take only one CPU cycle. for example:

int remainder = value % 1024;

it can be translated into:

int remainder = value & 0x3FF;
int remainder = value & (1024-1);

in general, If divisor n is power of 2, the modulo operators can be translated into bitwise AND with divisor - 1.

What is the real impact of modulo operator:

Marco Ziccardi wrote a program to answer this question:

int main(int argc, char** argv) { 
    int remainder;
    int value = 1301081;
    int divisor = 1024;
    int i = 0;
    while (i < 10000000) {
        remainder = value % divisor;
        i++;
    }
}

And compared its execution times with the same program implemented using binary AND (&) operator. Results are shown below (1000 runs of the program for both % and & versions):

As you can see, in the average case the program with the modulo operation is 62% slower than the one using & operator.

Conclusion:

It is not always possible to avoid modulo operator in the favor of bitwise.

Not a believer inside the mosque, am I Nor a pagan disciple of false rites Not the pure amongst the impure Neither Moses, nor the Pharoh

Bulleya Ki jaana main Kaun Bulleya! to me, I am not known

Na main andar ved kitaabaan Na vich bhangaan na sharaabaan Na vich rindaan masat kharaabaan Na vich jaagan na vich saun

Not in the holy Vedas, am I Nor in opium, neither in wine Not in the drunkard’s intoxicated craze Neither awake, nor in a sleeping daze

Bulleya Ki jaana main Kaun Bulleya! to me, I am not known