Building Distributed Applications with Dapr

Today, the development of distributed systems has become an increasingly essential need. However, due to the complexity of these systems, developing and managing such applications presents challenges for us developers. Matters like communication between services and state management are not easy tasks. This is where Dapr (Distributed Application Runtime) comes into play, assisting us developers.

Dapr is a platform designed to make developing distributed applications easier and faster. With its provided features, we can perform tasks like communication between services, state management, and event publishing/listening more effortlessly. It even simplifies actor programming.

Actor Model - Microsoft Orleans

Object-oriented programming (OOP) is based on four fundamental concepts. These are: encapsulation, abstraction, inheritance, and polymorphism. Of these, encapsulation is the most important. It means that the internal data of an object can't be accessed from outside.

Imagine a product object with a stock property. To decrease the stock, we will need a DecreaseStock method. The stock cannot be manipulated from outside, and will be decreased using the DecreaseStock method, which has business rules. But what happens if multiple threads enter the DecreaseStock method at the same time? No one knows how much stock will be decreased.

The reason for this is the shared memory problem, which is the biggest disadvantage of OOP. Of course, there are many ways and approaches to overcome this. The classic method is the locking mechanism, but since it is a very costly operation, it is necessary to avoid it. The Actor model not only saves us from the locking cost, but also allows us to develop in a distributed environment as if it were not distributed. But how does it do this?

Domain Driven Design - Tactical Patterns

DDD is an approach for software that have high complexity. This approach eliminates the complexities within the process of developing software. DDD is broken down into two categories, strategical and tactical. Strategic pattern is the main component of DDD. But we will not be talking about strategic pattern in this post. Tactical Pattern deals with architecture. It is about how classes, methods and dependencies should be. So we can call it clean architecture. Lets start then.

Test Driven Development

TDD Cycle

TDD tells that a test case should be written first, then the code should be written.

TDD is a cyclical process and includes three stages: RED, GREEN, REAFTOR. In the RED stage, a test case is written and executed. The test case fails. In the GREEN stage, first code is written for the test case to pass. The code doesn't need to be clean. The main goal is to write the simplest code for the test case to pass. The test case is run again. If the test is successful, the REFACTOR stage is started. At this stage, if the code can be refactored, it is done. The test case is run again. If the test case fails, the code is refactored. This cycle is continued until the code becomes desired.

What is Modular Monolith?

Traditional Monolith

Firstly, let's talk about Traditional Monolith approach. This approach focuses on layers. It includes three layers, UI, Business and Data. All features in a project are vertically separated into these layers. Among those three layers, the business layer is the one that contains business logics of all features. Each feature knows business logic of other features, which is a fact we call tightly coupled.

Developing Blockchain App – #2 Interaction with UI

In the previous post, we prepared the contract and wrote the test codes. In this post, we will make the contract interact with UI and call the functions defined in the contract. If you haven’t read the previous post, you can reach it from the following link.

Developing Blockchain App - #1 Create Smart Contract

This series of articles will consist of 3 parts. In these articles, we will develop a Dapp (decentralized application). It will be like Hands-on Labs. This article is about creating smart contracts.

Smart Contract ve Solidity

Smart Contracts are code parts that run in a blockchain network and store data. So it is a structure that contains both codes and data. Solidity is a programming language that enables us to write contracts.

Bootstrap Filter Plugin

Instead of the form elements being displayed side by side, it allows the form element to be displayed with the user action.

ASP.NET Core Feature Management

Feature Management provides feature management in .NET Core applications. It allows the management and querying of the active / passive status of the features of the application. For example, you can ensure that a feature you have just developed is active in a certain date range. To give another example, you can ensure that a feature you have developed is active with a certain percentage. Like A/B testing.

Event Sourcing with ASP.NET Core - 02 Messaging

1. Introduction

Since this article is second part of the article below, I recommend you to read the following article before starting. We will continue with the sample project in the article below.

In the previous article, we made the example of Kanban Board. By creating a RESTful API, we wrote the create, assign, move and complete endpoints. We recorded the requests coming to these endpoints as an event in the Event Store. So we focused on the store part of the Event Store. In this article, we will focus on with the messaging part.

We will include the following endpoint in our RESTful API endpoints.

[GET] api/tasks/{id}