Scala

ZIO Log Annotations Are Confusing

I was working on a logger that writes metrics every time a warning or an error is logged. I tried to provide additional metric tags depending on the log annotations. And it didn't work. I was adding an annotation and I could see its value somewhere deep in the stack trace but the annotations value was empty.

Turned out that ZIO has two log annotation mechanisms that work in parallel.

Static Sites

Tech Stack of the urmaul.com Blog

At the time of writing this, urmaul.com is a static blog with privacy-friendly dynamic elements. Everything runs self-hosted on a single virtual server with an automatically updated Linux.

This is a description of every layer with some reasoning and configuration details.

Scala

4 Ways to Fail at Measuring Durations

This post is a confession about multiple overlapping mistakes we made when trying to measure API request times. These errors went unnoticed for months because wrong statistics still look realistic. Hopefully, this post will help you avoid such fails.

Algorithms

Solution for Hackerrank Problem: Basic Cryptanalysis

There's one programming puzzle I solved many years ago but I still remember it because of the unusual solution. Problem: You have a text encrypted with a simple monoalphabetic substitution cipher. You don't have the key but you have a dictionary. Every word in a text can be found in this dictionary. Find the original text. It can be solved by dynamically generating regular expressions.

Algorithms

Solution for Project Euler Problem #700: Eulercoin

Problem: Imagine a sequence 1504170715041707*n mod 4503599627370517 where n is an integer increasing from 1. Find the subsequence of this sequence where every next element is smaller than the previous one.

All the solutions I've read about include brute force calculations. I found a better one, and I can't stop myself from posting it.

Yeoman

Generating CI/CD Pipelines for Microservices With Yeoman

TL;DR: You can create a Yeoman generator for your CI/CD pipelines. It's good, I tried.

Once you start multiplying services, you hit a problem of increased effort spent on non-business logic. With every new application you need to setup all the boilerplate: initial project, dependencies, running tests, building and deploying everything. Most of this things are very similar from project to project but they differ in details so you can copypaste a lot but you need to do it carefully so you don't break a lot of stuff by forgetting to update one line in a copypasted file. This needs a better solution.

TypeScript

A Good Way How to Validate Types in TypeScript

TL;DR: I've created a typescript library fp-ts-type-check. You can use it to validate the structure of data you get from outside of your application.

Here's the situation: your typescript application needs to retrieve some object via some API. You make an API request and you get a successful response with some json. Probably it's the data you expect but you can't say for sure. Your actions?

A Story About Rubber Ducks and Functional Programming

Once upon a time, I wanted to get a rubber duck. One rubber duck. I spent a lot of time looking for a perfect yellow rubber duck not representing any character and finally, I have found and bought it.

Later I accidentally found a much better rubber duck. I bought it also. That's one more rubber duck than I but I wasn't cruel enough to throw first one away. A big mistake.

PHP

PHP Doesn’t Want You to Do Microservices

As a PHP developer, I should probably rejoice when someone's saying "we do microservices in PHP". I don't. I'm fine with PHP and I like microservices but the combination is just bad. PHP is a tool for solving a narrow range of tasks (i.e. making websites) and if you're trying to do something out of this range (i.e. making microservices) — you're gonna have a bad time.

In this post, I tried to collect all microservice-related PHP problems I saw over the years.

Scala

Functional FizzBuzz in Scala With Streams and Higher Order Functions

I'm currently learning functional programming with scala and as a practice I've implemented FizzBuzz. To be honest, I made three different implementations of FizzBuzz but only the third one is good.

Stream.from(1) # Create infinite lazy stream from 1
  .map { (_, "") } # convert it to (number, word) tuple
  .map { x => if (x._1 % 3 == 0) (x._1, x._2 + "Fizz") else x } # Add "Fizz" to each 3rd word
  .map { x => if (x._1 % 5 == 0) (x._1, x._2 + "Buzz") else x } # Add "Buzz" to each 5th word
  .map { x => if (x._2 != "") x._2 else x._1.toString } # Take word or number
  .take(30) # Limit stream length
  .foreach(println) # Run everything and print results

It's even much better than usual imperative implementation and here's why.

TypeScript

React Styleguidist Usage Examples in Typescript Files

React Styleguidist uses external Markdown files to store usage examples. We wanted to use TypeScript for examples because reasons and we managed to do this with horrible solution. It includes custom webpack loader that parses TypeScript file with regular expressions and converts it to markdown. You could find parts of our code below.

PHP

Finding Overlap Among Groups of Date Ranges

Imagine you have two groups of date ranges and you want to determine whether they overlap.

Nah, let's make it harder. Imagine you have two groups of include date ranges and two groups of exclude date ranges. Your task is to determine, whether there's a date that is present in both include groups and not present in exclude groups. How to do that?

Bash

Running Bash Commands in Parallel

Let's imagine you have a script like below and you want to make it faster.

#!/bin/bash

echo "Started at `date +%Y-%m-%d\ %H:%M:%S`"

echo "Starting job 1"
sleep 5

echo "Starting job 2"
sleep 5

echo "Finished at `date +%Y-%m-%d\ %H:%M:%S`"

If it's ok to run jobs in parallel, you can easily do it with bash background jobs.

PHP

3 Ways to Make Your API Slow

I had to fix performance issues of one API endpoint. A pretty Symfony endpoint that gathers some data from database, assembling it to some structure and returns it as json.

Performance started being an issue when major part of that "some data" started to be 60000 entities. In worst case response time was almost 20 seconds. "Ok", I thought, "60k is a big enough number to make it slow". But trace showed that retrieving data from DB isn't a slowest part. There were things taking almost 1/3 of request time each. And these things were easy to fix.

PHP

Harmful Technical Interview Questions

Junior dev's life is hard an full of dangers. You come to technical interview and think "at least I'll learn something new from guys that know it better than me". Well, not really. Threre are some things that are ok in interviews and are totally wrong in real life. Here are some examples.