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What is an Event sourcing design pattern?

What is an Event sourcing design pattern?

What is an Event sourcing

Design Pattern?

 

Today we will see what is an Event sourcing Design Pattern is.

Previously we saw about What is Microservice? and the principles followed while developing MSA and the available design patterns. also, we saw the Shared database design pattern.

Before understanding what is Event sourcing design pattern is, let us see why & when do we use the Event sourcing design pattern.

All application uses data to maintain the current state of the data by updating it, In the traditional Create, Read, Update & Delete (CRUD) model a data is read, then make some modification to It, and update the current state of the data with the new values – often by using transactions to lock the data.

 CRUD has its own limitations, below are a few such limitations.

  1. CRUD performs update operations directly against the data, which slowdowns the performance and limits the scalability.
  2. When multiple users read and updates the data, more likely conflict occurs since the update operations take place on single data.
  3. Unless there is a separate auditing mechanism that records the state of data as history or the state of the data is lost.

Now, this is why & when we need to use an Event sourcing design pattern.

Event sourcing design pattern:

Event Sourcing gives us a new way of persisting application state as an ordered sequence of events. We can selectively query these events and reconstruct the state of the application at any point in time. Of course, to make this work, we need to reimage every change to the state of the application as events:

What is an Event sourcing design pattern?

Event sourcing design pattern

Example:

Consider we have Order and Cart services, When the Client adds the item to the cart or remove the items from the cart, these are called events, These events must be stored in order to maintain the changes made to the cart.

The events are persisted and published into the Event queue. Where the other services will subscribe to those events to get the updated state of the cart.

Consider you add the item to cart from Mobile App, then you login to website via PC and make some changes to the cart, these are captured as events and maintaining the seamless experience when accessing the cart in different platform.

 

In the next article, we will see the Branch design pattern.

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WeCanCode-Author

WeCanCode-Author

November 18, 2021

Senior Developer | Java & C#.NET | 10++ years of IT experience.

Planning to learn ReactJS or Angular or Flutter.!

What is Shared Database Design pattern?

What is Shared Database Design pattern?

What is Shared Database

Design Pattern

 

Today we will see what is Shared Database Design Pattern is.

Previously we saw about What is Microservice? and the principles followed while developing MSA and the available design patterns. also, we saw Asynchronous Messaging Design pattern.


What is Shared Database Design Pattern?

For every web service application, there is a massive amount of data present. So when the application is broken down from monolithic to microservice, It is necessary that each application have a sufficient amount of data to process the request.

So, we can have a database for each service or it can have a shared database.

Yes, we can use a database per service or shared database to solve many problems.

Below are a few of the problems,

  • Data duplication and inconsistency
  • Different application has different storage requirements and different infrastructure.
  • Few transactions can query the data with multiple services.
  • De-normalization of data

In order to solve the first 3 problems, we can go for database per service, as it will be accessed by the microservice API itself.

So each web service will have its own databased ID, which the other services do not have direct access to.

📌 Note: Limit the number of databases to 2-3 for the microservices; else, scaling up will be a problem.

What is Shared Database Design Pattern?

Shared Database Design Pattern: Example

Example:

Example1: Partially having a shared database for the microservices.

In the above image, If you see the Contact & Student services shares a database but whereas Fees has its database. (While designing the MSA for the application we can decide about how our application can utilize the database).

Example 2: Partially having a shared database for the microservices.

In the next example, if you see the image, the entire microservices uses the one common shared database. this way the database is one and multiple services use it to persist or read data.

In the next article, we will see Asynchronous Messaging design pattern.

 

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WeCanCode-Author

WeCanCode-Author

November 14, 2021

Senior Developer | Java & C#.NET | 10++ years of IT experience.

Planning to learn ReactJS or Angular or Flutter.!

Add Image to Android app

Add Image to Android app

Add PNG Icon to Android app

 

In this article, let discuss on

Add PNG Icon to Android app

Let us see how to Add PNG icon to Android App. In the end you your app will use the icon you have added for the android application.

 In this article I’m going to use the existing android project created as part of this article Make WordPress as Android App. This Follow the code repo used  ).

How to Add PNG Icon to Android App?

You can add Image assets by Right click on the location where the image or icon need to be placed.

See below screenshot for the Menu option in Android Studio.

  • After right-click drawable folder, Choose New > Image Assets
  • You need to choose the image or icon from the browse menu under Source Asset section of Foreground Layer Tab.
  • Adjust the Scaling according to the image or icon output.
  • Go to Background Layer tab and adjust the background color or image accordingly.
  • Once done, click Finish (Note: Try to keep the same name as the previous icon file name, if you are replacing the icon)
  • Run the App to see the new Icon changed.
intellij add image asset menu
WeCanCode-Author

WeCanCode-Author

October 22, 2021

Senior Developer | Java & C#.NET | 10++ years of IT experience.

Planning to learn ReactJS or Angular or Flutter.!

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