Rafael Ponte rponte

Interesting articles and content about data partitioning

Slotted Counter Pattern

Some articles and tips about Slotted Counter Pattern:

PostgreSQL Lock Contention For Frequently Updated Rows
- Example of how partitioning a counter can improve throughput without giving up locks
PlanetScale: The Slotted Counter Pattern
Hacker News: The Slotted Counter Pattern

Race conditions, locking e bancos de dados relacionais

Pretendo apresentar um código com uma lógica de negócio simples que funciona bem na perspectiva do negócio mas que quebra miseravelmente em ambientes minimamente concorrentes. Para isso, vou demonstrar através de testes de integração como identificar o Race Condition no código e principalmente como resolvê-lo através de mecanismos de locking e Isolation Level do seu banco de dados;

O que vamos discutir

Por que estudamos esse assunto mais a fundo?
- 1.1. Bootcamp Seniors
- 1.2. Handora: Curso CRUD e Atualizações Concorrentes com JPA/Hibernate - by Jordi Silva

1.3. A importância do treino: o que eu levei alguns bons anos para aprender o Jordi levou 6 meses

Create Repository Gitlab

Creates a new repository (aka project) in a specific Gitlab group.

How to set up this project

This project was developed with Python v3.9, and it also uses Python's Virtualenv tool. So before working on this project we need to set up it.

Inside this project's folder, execute those commands to configure your environment:

The issue with SSL certificate

Just out of the blue, I started getting this issue ("server certificate verification failed. CAfile: none CRLfile: none") while trying to clone any Github repository on Linux (WSL2):

git clone https://github.com/rafaelpontezup/preventing-lost-update-racecondition.git
Cloning into 'preventing-lost-update-racecondition'...
fatal: unable to access 'https://github.com/rafaelpontezup/preventing-lost-update-racecondition.git/': server certificate verification failed. CAfile: none CRLfile: none

And also with Window 11 I got "SSL certificate problem: unable to get local issuer certificate":

Distributed Polling with SKIP LOCKED

	-- (This code was run in PostgreSQL 9.6.1)
	-- Demonstration of how serializable isolation for PostgreSQL, which detects possible
	-- interference between concurrent transactions, can produce false positives

	-- in psql, create the following table

	CREATE TABLE users(
	id SERIAL NOT NULL PRIMARY KEY,
	username VARCHAR NOT NULL
	);

	/**
	* This Spring Boot controller was implemented as an example of a simple but robust idempotent REST API that
	* leverages the ACID properties of a relational database.
	*/
	@RestController
	public class CreateNewUserController {

	@Autowired
	private UserRepository repository;
	@Autowired

	package br.com.stackspot.nullbank.withdrawal;

	import org.hibernate.LockOptions;
	import org.springframework.data.jpa.repository.*;
	import org.springframework.stereotype.Repository;

	import javax.persistence.LockModeType;
	import javax.persistence.QueryHint;
	import javax.transaction.Transactional;
	import java.util.Optional;

	package br.com.zup.edu.ifoodwebapp.samples.books;

	import base.SpringDataJpaIntegrationTest;
	import org.junit.jupiter.api.BeforeEach;
	import org.junit.jupiter.api.DisplayName;
	import org.junit.jupiter.api.Test;
	import org.springframework.beans.factory.annotation.Autowired;
	import org.springframework.dao.DataIntegrityViolationException;
	import org.springframework.transaction.TransactionSystemException;

	import javax.persistence.*;
	import javax.validation.constraints.NotBlank;
	import javax.validation.constraints.Size;

	import org.hibernate.validator.constraints.ISBN;

	import java.util.Objects;

	import static org.hibernate.validator.constraints.ISBN.Type.ISBN_13;