The core for asynchronous programming are the objects Task and Task<T>. Both of them are compatible with the keywords async and await.

First of all we need to identify if the code’s I/O-bound or CPU-bound.

• the code’s limited for external operations and waits for something a lot of time. Examples of this are DDBB calls, or a server’s response. In this case we have to use async/await to free the thread while we wait
• the code does a CPU-intensive operation. Then we move the work to another thread using Task.Run() so we don’t block the main thread.

async code vs parallel code

(!) Asynchronous code is not the same as parallel code (!)

• In async code you are trying to make your threads do as little work as possible. This will keep your app responsibe, capable to serve many requests at once and scale well.
• In parallel code you do the opposite. You use and keep a hold on a thread to do CPU-intensive calculations

async code

The importante of async programming is that you choose when to wait on a task. This way, you can start other tasks concurrently

In async code, one single thread can start the next task concurrently before the previous one completes.
(!) async code doesn’t cause additional threads to be created because an async method doesn’t run on its own thread. (!) It runs on the current synchronization context and uses time on the thread only when the method is active.

parallel code

For parallelism you need multiple threads where each thread executes a task, and all of those tasks are executed at the same time

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JavaScript library for building user interfaces. Created by Facebook.

Yarn

JavaScript package manager compatible with npm that helps automate the process of installing, updating, configuring, and removing npm packages.

Install

# add Yarn repository
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -  

echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list  

sudo apt-get update  
sudo apt-get install nodejs yarn  
yarn --version # verify

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Which problem does it solve?

1. Whenever I started a new project, I would spend the first few days setting everything up - Java11 (.NET with c# nowadays), maven configuration, docker, microservices communication, databases config etc. This process took way too much time.

2. When learning a new programming language or framework, by the time I needed to use it, I had often forgotten how to set everything up. This approach saves me time in the long run and forces me to really learn how to use the new technology.

3. For technical tests during job hunting, it allows me to save time and focus entirely on the code challenge.

Link

Github Repository

Jekyll is a blog-aware static site generator, written in Ruby. It’s used for Github Pages and it transforms files written in markdown and liquid into a full HTML web.

Installation

Pre-requirements

sudo apt-get install ruby-full build-essential zliblg-dev
sudo gem install jekyll bundler

Configuration

The basic config is under _config.yml

# shows any config mishap
bundle exec jekyll doctor

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List of things to do, to improve your Docker experience

Never map the public port on a DockerFile

If you map it, you’ll only be able to have one instance of this container running. If the user wants to map the port, he’ll be able to do it in a compose script or with -p option.

# public and private mapping
EXPOSE 80:8080 # don't do this

# private mapping
EXPOSE 80

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Working docker-compose and DockerFile examples to complement this information
Interesting tool to analyze custom Image layers size

Basic Definitions

Image Executable package that includes everything needed to run an application. It consists of read-only layers, each of which represent a DockerFile instruction. The layers are stacked and each one is a delta of changes from the previous layer.
Container Instance of an image.

Stack Defines the interaction of all the services
Services Image for a microservice which defines how containers behave in production

DockerFile File with instructions that allows us to build upon an already existing image. It defines:

• the base image to build from
• our own files to use or append
• the commands to run

At the end, a DockerFile will form a service, which we may call from docker-compose or standalone with docker build.

DockerFiles vs docker-compose A DockerFile is used when managing a single individual container. docker-compose is used to manage an application, which may be formed by one or more DockerFiles. Docker-compose may also be used as support to input large customization options, which otherwise would be parameters in a really long command.

You can do everything docker-compose does with just docker commands and a lot of shell scripting

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This are my Rust posts, as I wanted to test it briefly as a backend language.

1. From Java to Rust
2. Rust installation
3. Rust experience sheet

Config

• see config git config -l
• modify username git config --global user.name "newName"
• modify email git config --global user.mail "new@mail.com"

Git bisect

Is a tool to find the exact commit where a bug was introduced.

Usage

I have a file with the following content and an obvious bug

Row row row your car at the river

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Rest levels

Model of restful maturity used to help explain the specific properties of a web-style system.

Level 0

The starting point for the model is using HTTP as a transport system for remote interactions, but without using any of the mechanisms of the web.
We publish a document on how to use our API. We declare only one endpoint and do all the communication through this endpoint.

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Template

This is all needed to test.

package main

func main() {

}

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Check installation

go version

Environment variables

GOROOT
Folder where go was installated. It must only be set when installing to a custom location.

GOPATH
Place to get, build and install packages outside the standard Go Tree.

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