Chapter 1 : Overview

Tutorial For Cloud Native Development with use case of Building SaaS Multitenant using Enterprise Microservices and Tenant Specific Customizations.

Getting Started

Its recommended to undertake below tutorial first , if you are fresher or Learning to Code :

• Build Your First App

Also familiarize with and get done on its:

• Tutorial Prerequisites

Cloud Native Development Tutorial

Tutorial Contents

What will be developed ?

Tutorial will cover below microservices development:

• Enterprise Microservices Development
  • Enterprise Microservices
  • Build Main Product Microservices V1
    • Synchronous Communications Based Microservices
      • Using REST WebClient and Helper Microservices
• SaaS Multitenant
  • Extend Enterprise Microservices
    • Extend Main Product Microservices V2
      • with Tenant Manager Customization Services
  • Tenant Specific Customization Using Microservices
    • Synchronous Communications Based Customization Using Microservices
      • Using REST WebClient and Tenant-specific Microservices
    • Event-Based Customization Using Microservices
      • Using Kafka Events and Tenant-specific Microservices
• BFF Backend For Frontend

Microservices Tech Stack

Tech Stack: Java 17 Spring Boot 3 Database: PostgreSQL Ver 8.2+ API Type: REST

Use Case - Ordering System - Enterprise SaaS Multitenant

Sample Tables

Enteprise microservices sample table SQLs.

• Sample Enteprise Microservices Tables SQL - For MySQL
• Sample Enteprise Microservices Tables SQL - For PostgreSQL

Tables in SQL script

• customer
• tenant
• product
• inventory
• orders
• shipping

SaaS Multitenant

Building SaaS Multitenant using Enterprise Microservices and Tenant Specific Customizations

Software Requirements Specification

User Stories

• Main Product V1 Features

Feature	Service	Input	Output
Create Order	order-service-v1	customerId, tenantId, productId, orderQuantity	orderId, orderStatus
↓ → Call Check Inventory Quantity exists for Order fullfillment	inventory-quantity-check-service	productId, orderQuantity	quantityAvailable (true/false)

- inventory-quantity-check-service
    - If quantity available, deduct quantity from inventory and write LOG entry
        - Inventory Consumption: productId: 2, orderQuantity: 10

• Main Product V2 Features Plus
  • Tenant Specific Customization

Feature	Service	Input	Output
Create Order and Handle Tenant Customizations, if any	order-service-v2	customerId, tenantId, productId, orderQuantity	orderId, orderStatus
↓ → Call Check Inventory Quantity exists for Order fullfillment	inventory-quantity-check-service	productId, orderQuantity	quantityAvailable (true/false)
↓ → Call Check Tenant Specific Customizations	tenant-manager-cust-service	customerId, tenantId, productId, orderId, orderQuantity	orderId, orderStatus
↓ → If Tenant 2, call - Check orderQuantity is > 5	tenant-2-validation-service	orderQuantity	validationPass (true/false)
↓ → If Tenant 3, send order event, which shipping service will consume and create shipping entry		customerId, tenantId, productId, orderQuantity	order event sent
Shipping service will poll for and consume order event, then will create shipping entry	tenant-3-shipping-service	order event ( customerId, tenantId, productId, orderQuantity)	shippingId (shipping entry)

- tenant-3-shipping-service
    - Upon creating shipping entry, write LOG entry
        - Order Event Consumed : customerId: 1, tenantId: 2, productId: 2, orderId: 3
            - Shipping Created : shippingId: 2

Enterprise Microservices Design

Microservices for BFF Backend For Frontend

	Services	Backend Project	Port
BFF	emapi-BFF-service	emapi-BFF	9060

Microservices for Main Product and Customizations

• Architecture Model

Product		Service				Service
Main Product		[ Order Service ]	→ ←	sync	→ ←	[ inventory-quantity-check-service ]
		↑ ↓ sync
Tenant Customization		[ Tenant Manager ] [ + Customization Service ]	→ ←	sync	→ ←	[ tenant-2-validation-service ]
		↓ → async	→	event message queue	→	[ tenant-3-shipping-service ]

• Microservices Details

	Services	Backend Project	Port
Main Product	order-service-v1	emapi-order-svc-v1	9070
	inventory-quantity-check-service	emapi-inv-check-svc	9072
Tenant Customization	order-service-v2	emapi-order-svc-v2	9070
	tenant-manager-cust-service	emapi-tenant-mgr-cust-svc	9074
	tenant-2-validation-service	emapi-tenant-2-svc	9076
	tenant-3-shipping-service	emapi-tenant-3-svc	9078

Microservices Communications

Microservices Communicate With Details

	Services	Port	Communication Mode	With Service	Port
Main Product	order-service-v1	9070	synchronous-webclient	inventory-quantity-check-service	9072
Tenant Customization	order-service-v2	9070	synchronous-webclient	tenant-manager-cust-service	9074
	tenant-manager-cust-service	9074	synchronous-webclient	tenant-2-validation-service	9076
	tenant-manager-cust-service	9074	asynchronous-event	tenant-3-shipping-service	9078

Considerations

• Enterprise Microservices can be developed with low code customizations after using EasyManage Builder and generating code.
• Security is skipped for tutorial purposes
• Frontend Flutter app can be used for providing mobile app
• BFF Backend For Frontend for mobile app is directly available after code generation.
• The code generated from EasyManage can be cleaned, leaving what is required for the microservices, as by default generated code contains lot more features and GraphQL APIs also.