Mar 3, 2021

But it works on my machine! 🤷‍♂️

By Apoorv Tyagi • Issue #4 • View online

Welcome to the fourth issue of The Trojan’s Wednesday Wisdom newsletter. I hope you all had an amazing last week.

Today let’s talk a little about Docker 🐳

I’ll be sharing some common terminologies and useful commands that will help you get started with it.

So get a cup of coffee☕ and let us begin

What is Docker?

Have you heard of this famous phrase, “It works on my machine”?

In simplest term, this is the problem that Docker solves.

Docker makes it easier to build, deploy and run applications using containers.

Containers, which is a standard unit of software allow us to package all the things that our application needs, such as libraries and other dependencies and ship it all as a single package.

In this way, our application can run on any machine and have the same behavior.

FUN FACT - The whale’s name in Docker’s logo is “Moby Dock” 🐋

Terminologies

Images are the blueprints of the application which form the containers. You docker pull an image.
Containers are created images. They run the actual application.
Dockerfile is a simple text file that contains a list of commands that the Docker client calls while creating an image.
Docker Hub is a registry of Docker images.
Daemon is the background service that manages the containers.

Useful Commands

docker run [IMAGE]

Pulls and runs image.

docker run -it to run interactive
docker run -it sh to run shell commands inside container
docker –rm removes the container once run
docker –detatch will let container run in the background
docker image prune -a to delete all images
docker –publish-all will publish all exposed ports to random ports
docker run –port 8000:80 to specify a custom port. Ports are in the format of LOCAL_PORT:DOCKERFILE_PORT

docker push [IMAGE]

To push Docker image to Docker Hub.

docker build

Build docker image.

docker build –tag username/project-name . to add tag name

Containers

docker start [containerID] to start a container
docker stop [containerID] to stop a container
docker ps –all to list all containers
docker ps to list all running containers
docker exec -it [containerID] [filename] to explore files inside a container
docker rm [containerID] to delete container.

Now, If you want a more hands-on tutorial on Docker, I have written a nice article on that too.

📃In the blog post below, I have shown how you can containerize your application and even get it running on Kubernetes (Which is a famous container orchestration tool).

The theoretical introduction that I just gave you is enough pre-requisite for this tutorial.

This is how the roadmap looks like.-

(You can leave the last step if you’re not very comfortable with Kubernetes).

Containerize your web application & deploy it on Kubernetes

If you are new to the concept of containers and the Docker & Kubernetes platform, chances are you will find plenty of theoretical resources online but there is a huge gap when it comes to practical tutorials. This blog post is aimed to…

apoorvtyagi.tech • Share

Finishing what we left last week 🕚

In last week’s newsletter, I have shown you this image and asked you to identify the bug in the code 💻

So were you able to find out what’s wrong?

The best part here is that only one character fixes this code and guess what it is…🤔

A semicolon(;) 🤦‍♂️

Just by inserting a semicolon after our first function ends, It will work, and you’ll see “Hello World!” in your console.

But Why? 🤯

Because without that semicolon, the last function is interpreted as an argument to the first function call.

Here’s a rewrite that demonstrates what’s going on when the code is run without the semicolon 👇

There are 3 function invocations in that last line:

f1 is called with no arguments.
The return value of f1() is called with f2 as its argument.
The return value of f1()(f2) is called with no arguments.

Since the return value of f1() is not a function, the runtime throws a TypeError during the second invocation.

With the semicolon added, this becomes 👇

Which now runs as expected🙂

Moral Of The Story - “Always use semicolons”

Relying on Automatic Semicolon Insertion(ASI) is not encouraged, This is even included in Google’s, Airbnb’s, and jQuery’s Javascript style guides.

That’s it from my side for this week. I hope you enjoyed what I included this time and have learnt something new🤞

🍻 Consider subscribing in case you haven’t already and share this newsletter with those you feel can get benefit out of it.

👋 See you on the Internet next Wednesday!

-Apoorv;

Did you enjoy this issue?

By Apoorv Tyagi

𝗔 𝗻𝗲𝘄𝘀𝗹𝗲𝘁𝘁𝗲𝗿 𝗮𝘁 𝘁𝗵𝗲 𝗶𝗻𝘁𝗲𝗿𝘀𝗲𝗰𝘁𝗶𝗼𝗻 𝗼𝗳 𝐏𝐬𝐲𝐜𝐡𝐨𝐥𝐨𝐠𝐲, 𝐓𝐞𝐜𝐡 𝗮𝗻𝗱 𝐒𝐨𝐟𝐭𝐰𝐚𝐫𝐞 𝐄𝐧𝐠𝐢𝐧𝐞𝐞𝐫𝐢𝐧𝐠.

𝗝𝗼𝗶𝗻 𝟭𝟬𝟬+ 𝗺𝗲𝗺𝗯𝗲𝗿𝘀 𝐭𝐨 𝐢𝐦𝐩𝐫𝐨𝐯𝐞 𝐚𝐬 𝐚 𝐝𝐞𝐯𝐞𝐥𝐨𝐩𝐞𝐫 𝗮𝗻𝗱 𝐭𝐨 𝐠𝐞𝐭 𝐭𝐡𝐞 𝐛𝐞𝐬𝐭 𝐭𝐢𝐩𝐬 𝐚𝐧𝐝 𝐚𝐫𝐭𝐢𝐜𝐥𝐞𝐬 𝗱𝗶𝗿𝗲𝗰𝘁𝗹𝘆 𝘁𝗼 𝘆𝗼𝘂𝗿 𝗶𝗻𝗯𝗼𝘅 📩

P.S. It is free (and fun!) :)

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