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📚 Micro services Architecture and Design patterns.
📚 Data Structures and Algorithm
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Today we will see what are the Saga Design Pattern and types available.
Previously we saw about What is Microservice? and the principles followed while developing MSA and the available design patterns.
The Saga Pattern is a microservices architectural pattern to implement a transaction that extends multiple services.
A saga is a sequence of local transactions. Each service in a saga performs its own transaction and publishes an event. The other services listen to that event and perform the next local transaction. If one transaction fails for some reason, the saga also executes compensating transactions to undo the impact of the preceding transactions.
Consider a Food delivery service flow, When a user places an order, below could be the flow.
December 07, 2021
Senior Developer | Java & C#.NET | 10++ years of IT experience.
Planning to learn ReactJS or Angular or Flutter.!
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.
Now, this is why & when we need to use an 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:
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.
November 18, 2021
Senior Developer | Java & C#.NET | 10++ years of IT experience.
Planning to learn ReactJS or Angular or Flutter.!
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.
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.
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.
Shared Database Design Pattern: Example
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).
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.
November 14, 2021
Senior Developer | Java & C#.NET | 10++ years of IT experience.
Planning to learn ReactJS or Angular or Flutter.!
Previously we saw about What is Microservice? and the principles followed while developing MSA and the available design patterns. also, we saw an API Gateway design pattern.
Today we will see what is Asynchronous Messaging Design Pattern is.
Previously we saw about Chained or Chain of responsibility design pattern which makes the client wait for a long time, It also breaks the chain if any one service goes down and cause a bad experience for the clients.
To avoid such bad experiences for the client, The Asynchronous design pattern can be used, which communicate with the available services using message queue or event driven approach and not sequentially.
Yes, Messaging or events, The Asynchronous design pattern uses the Messaging Queue (MQ) or Event driven like ActiveMQ, RabbitMQ, Kafka and other tools for its communication with other services.
Consider we have Cart, Product, Stock, Order & Shipping services.
When the Product is added to the Cart, Stock must be updated accordingly, So the Product calls stock via Message Queue.
And then Order calls shipment via Message Queue to prepare a label for shipment.
This way the client need not wait for the flow of service to be completed to get the response immediately.
November 11, 2021
Senior Developer | Java & C#.NET | 10++ years of IT experience.
Planning to learn ReactJS or Angular or Flutter.!