Being a web application, it is highly dynamic and it needs to be scalable with minimum efforts put to integrate it in the existing environment. Hence in this scenario building a large scale web based distributed system, micro-services architecture emerged in recent years. Through this project I wish share my early experience with micro-service architecture to design a scalable Health Analysis/Management platform with recent industry recently developed and most used services for load balancing, monitoring, API proxy,security, etc. and compare the benefits and challenges of distributed systems with traditional monolith architectures.

1. Run Code on PC
2. Layered Architecture
3. Infrastructure
4. Database Configuration
5. Context Diagram
6. Actual Database Configuration Theory
7. Deliverables
   • Forum API
   • Appointment Management API
   • Store Locator API
   • Diagnosis API
   • Medication API
   • Authentication and Authorization API
   • Mailing API
8. Gateways
9. Microservice Tenents
   • Circuit Breaker (Fault Tolerance)
   • Service Registry and Discovery
   • Load Balancing
10. Run Code on PC

1. As depicted in above figure the architecture is divided into 3 sections each having its own set of responsibilities :

   • API Service layer : responsible for performing authorization and load balancing for next level of processes.
   • Composite Layer : responsible for performing abstraction and acts as a single point of contact for the external requests. It also manages circuit breaking process to increase fault tolerance
   • Core Layer: consists of core services supported by the system which includes managing cache, database and business logic.

The Schema configuration is simulated as per the following diagram below :

Note : Word Simulated is used since basic SQL constraints are not possible on database per service architecture.

Below is Context Diagram for better understanding of the overall working of the system,

• Reasons why traditional database cannot be used in Microservice architecture:

  • Services must be loosely coupled so that they can be developed, deployed and scaled independently
  • Some business transactions spans multiple services. For example, every service uses User Service for security purpose
  • Some business transactions need to query data that is owned by multiple services.
  • Databases must sometimes be replicated in order to scale.
  • Different services have different data storage requirements. For some services, a relational database is the best choice and for some No Sql.

• Solution to above problems

  • Keep each microservice’s persistent data private to that service and accessible only via its API.
  • The service’s database is effectively part of the implementation of that service. It cannot be accessed directly by other services.
  • Database-server-per-service – each service has it’s own database server.
  • Helps ensure that the services are loosely coupled. Changes to one service’s database does not impact any other services.

Below listed are all the deliverabeles of the project:

1. Core Services

   • Forum API : This service is reponsible for managing community discussion forum
   • Appointment Booking API : This service is reponsible for managing appointment management with patient and doctor as end users.
   • Store Locator API : This service is reponsible locating nearby pharma stores.
   • Diagnosis API : This service makes call to django servers which consists of below services:
     1. Heart Attack Predictor API : This service is reponsible for taking in readings as input and returning diagnosis with probability.
     2. Stroke Risk Analysos API : This service is reponsible for taking in readings as input and returning diagnosis with probability.
     3. Diabetes Pridictor API : This service is reponsible for taking in readings as input and returning diagnosis with probability.
   • Medication Management API : This service is responsible for managing prescription of patient.

2. Support Services

   • Authorization and Authentication API : This API is responsible for performing Token based SSO authentication and authorization.
   • Mailing API : This API is responsible for dispastching mails to user whenever reuqired.
   • Proxy Server : This server is reponsible for proxying requests to application.
   • Service Discovery Server : This servers acts as Service Registry and helps in the process of service discovery.

3. Gateway Services

   • Catalog Service : This API acts as a gateway to the entire system and only authenticated requests can pass through this gateway.

• This API will enable user to implement forum service in any project. It is stand-alone service with independent endpoints.
• In order to make it work you need implement Authorization and Authentication API.

Json Format Example

{
    "name":"Thread Name",
    "description":"This is First Thread",
    "numberOfPosts":0
}

Json Format Example

{
    "subredditName":"Thread Name",
    "postName":"This is under First Subreddit",
    "url":"www.firstSubreddit.com",
    "description":"This is description post first seventh Subreddit"
}

Json Format Example

{
    "postId":1,
    "text":"This is a third comment for postId 1 under 1 subreddit"
}

Json Format Example

{
    "voteType":"UPVOTE",
    "postId":"1"
}

• This API will enable user to implement appointment booking, schdule checks and management. It is stand-alone service with independent endpoints.
• In order to make it work you need implement Authorization and Authentication API.

Json Format Example

{
    "pat_name":"Arnob_123",
    "pat_phone":"87171691191",
    "pat_dob":"03-09-1999",
    "pat_gender":"M",
    "enrollDate":"09-09-2020",
    "insured":"Y"
}

Json Format Example

{
    "pat_name":"Arnob_123",
    "pat_phone":"87171691191",
    "pat_dob":"03-09-1999",
    "pat_gender":"M",
    "enrollDate":"09-09-2020",
    "insured":"Y"
}

Json Format Example

{
    "docId":"testuser5",
    "appTypeId":1,
    "startDate":"2021-03-13",
    "startTime":"6:30:59",
    "endTime": "7:00:00"
}

Json Format Example

{
    "doc_name":"Arnob chowdhury",
    "doc_phone":"87171691191",
    "doc_address":"Valentus, Gaur City mall CR",
    "dateOfStarting":"1978-09-09",
    "doc_gender":"M",
    "doc_dob":"1978-09-09",
    "doc_settlePoint":"22.2323,45.4433",
    "doc_description": "Did MBBS and MD from Boston, Heart specialist",
    "docSpecId": 1,
    "clinicId": 1
}

Json Format Example

{
    "doc_name":"Ikala Chuhioq",
    "doc_phone":"8717123455",
    "doc_address":"Valentus, Gaur City mall CR",
    "dateOfStarting":"1978-09-09",
    "doc_gender":"M",
    "doc_dob":"1978-09-09",
    "doc_settlePoint":"22.2323,45.4433",
    "doc_description": "Did MBBS and MD from Boston, Heart specialist",
    "docSpecId": 1,
    "clinicId": 1
}

Json Format Example

{
    "doc_name":"Ikala Chuhioq",
    "doc_phone":"12345667890",
    "doc_address":"Valentus, Gaur City mall CR",
    "dateOfStarting":"1978-09-09",
    "doc_gender":"M",
    "doc_dob":"1978-09-09",
    "doc_settlePoint":"22.2323,45.4433",
    "doc_description": "Did MBBS and MD from Boston, Heart specialist",
    "docSpecId": 1,
    "clinicId": 1
}

• This API will enable user to implement appointment near geo search. It is stand-alone service with independent endpoints.
• It does not require Authorization and Authentication API and is accesscible to anyone.

Json Format Example

{
    "storeName":"books testing",
    "streetName":"NEw Street 1 ...",
    "location": {
      "type": "Point",
      "coordinates": [12.1212, -45.2331]
    }
}

• This API will enable user to call Django Server running Machine Learning Models to performs diagnosis on the input reading. It is stand-alone service with independent endpoints.
• It requires Authorization and Authentication API to be implemented prior to use.

Json Format Example

{
    "glucose":140.0,
    "insulin":0.0,
    "bmi":23.3,
    "age":50
}

Json Format Example

{
    "gender":1,
    "ever_married":1,
    "work_type":2,
    "residence_type":1,
    "smoking_status":1,
    "age":67, 
    "hypertension":0,
    "heart_disease":1, 
    "avg_glucose_level":229, 
    "bmi":37
}

Json Format Example

{
    "age":63,
    "sex":1,
    "cp":3,  
    "trestbps":145,  
    "chol":233, 
    "fbs":1,  
    "restecg":0,  
    "thalach":150,  
    "exang": 0, 
    "oldpeak":2, 
    "slope": 0,
    "ca":0,
    "thal":1
}

• This API will enable user to implement medication management for better pateint to store experience.

• It requires Authorization and Authentication API to be implemented prior to use.

Json Format Example

{
    "patId":"testuser4",
    "coordinates":[12.1212,-45.2321],
    "medication":[{
            "medName":"paracitalom",
            "time":"morning"
        },
        {
            "medName":"cyrus",
            "time":"night" 
        },
        {
            "medName":"cyrus_19191",
            "time":"night" 
        }
    ]
}

• Multiple services put together forms an application each of which are independent of others. Hence securing the system as a whole is not enough and poses a risk of whole system compromise if even just one service is compromised. Hence to address this issue, I implemented JWT based authentication and authorization for each μS that will allow requests after authenticating it from centrally runningauthentication and authorization server

• When user logs in using credentials, it is encrypted and is always attached with the payload while requests are made. It the responsibility of each service to decrypt the credentials and verify it against the centrally running authorization andauthentication server and allow only valid calls.

Json Format Example

{
    "username":"testuserd7",
    "email":"[email protected]",
    "password":"test789",
    "role":"DOCTOR"
}

Json Format Example

{
    "username":"testuser4",
    "password":"test456"
}

Json Format Example

{
    "username":"testuser4",
    "password":"test456"
}

• This API is responsible for dispastching mails to user in case of account activation, diagnosis outcome.
• It requires Authorization and Authentication API to be implemented prior to use.

• URI for gateway : https://localhost:8085
• URI for Authorization API : https://localhost:8082
• URI for Mailing API : https://localhost:8089
• URI for Forum-API : https://localhost:8081
• URI for Appointement Management API : https://localhost:8084
• URI for Store Locator API : https://localhost:8086
• URI for Medication API : https://localhost:8083
• URI for Diagnosis API : https://localhost:8088
• URI for TOM TOM (Third party) API : https://localhost:8087

• Services sometimes collaborate when handling requests. When one service synchronously invokes another there is always the possibility that the other service is unavailable or is exhibiting such high latency it is essentially unusable. Precious resources such as threads might be consumed in the caller while waiting for the other service to respond. This might lead to resource exhaustion, which would make the calling service unable to handle other requests. The failure of one service can potentially cascade to other services throughout the application.
• How to prevent a network or service failure from cascading to other services?

• A service client should invoke a remote service via a proxy that functions in a similar fashion to an electrical circuit breaker. When the number of consecutive failures crosses a threshold, the circuit breaker trips, and for the duration of a timeout period all attempts to invoke the remote service will fail immediately. After the timeout expires the circuit breaker allows a limited number of test requests to pass through. If those requests succeed the circuit breaker resumes normal operation. Otherwise, if there is a failure the timeout period begins again.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;


@SpringBootApplication
@EnableCircuitBreaker
@EnableHystrixDashboard
public class CatalogServiceApplication {

	public static void main(String[] args) {
		SpringApplication.run(CatalogServiceApplication.class, args);
	}

}

application.porperties Configuration :

hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=2000
management.endpoints.web.exposure.include=hystrix.stream
hystrix.dashboard.proxyStreamAllowList=*

• Services typically need to call one another. In a monolithic application, services invoke one another through language-level method or procedure calls. In a traditional distributed system deployment, services run at fixed, well known locations (hosts and ports) and so can easily call one another using HTTP/REST or some RPC mechanism. However, a modern microservice-based application typically runs in a virtualized or containerized environments where the number of instances of a service and their locations changes dynamically.
• How does the client of a service - the API gateway or another service - discover the location of a service instance?

• Each instance of a service exposes a remote API such as HTTP/REST, etc. at a particular location (host and port)
• The number of services instances and their locations changes dynamically.
• Virtual machines and containers are usually assigned dynamic IP addresses.
• The number of services instances might vary dynamically.

• Service Discovery Registry

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class ServicedisApplication {

	public static void main(String[] args) {
		SpringApplication.run(ServicedisApplication.class, args);
	}

}

• application.properties Configuration

eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
eureka.client.service-url.default-zone=https://localhost:8761/eureka/
eureka.instance.hostname=localhost
spring.cloud.loadbalancer.ribbon.enabled = false

• Service Discovery Client

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.scheduling.annotation.EnableAsync;


@SpringBootApplication
@EnableAsync
@EnableEurekaClient
public class RedditApplication {

	public static void main(String[] args) {
		SpringApplication.run(RedditApplication.class, args);
	}

}

• application.properties Configuration

eureka.client.register-with-eureka=true
eureka.client.fetch-registry=true
eureka.client.service-url.default-zone=https://localhost:8761/eureka/
eureka.instance.hostname=localhost

• In simple terms Load Balancer distributes the incoming traffic to multiple instancesof the service and works in conjunction to scaling process.
• Algorithm for load balancing: Round Robin
• Type of Load balancing: Hybrid Load Balancing
• In hybrid load balancing technique used in this project all the consumers and prosumers (one that produces result as well as requires input ) are implemented with theirown load balancer

@GetMapping("/get-stores") //hystrix
@HystrixCommand(fallbackMethod = "getNearByFB")
public Object getNearBy(@RequestHeader(value = "Authorization") String token){
	HttpHeaders headers = new HttpHeaders();
	headers.setContentType(MediaType.APPLICATION_JSON);
	headers.set("Authorization", token);
	HttpEntity<String> entity = new HttpEntity<String>(headers);
	
	String uri = loadBalancer.choose("medication-service").getServiceId();
	
	String url = "https://"+uri.toString() + "/medication/nearByStore";
	ResponseEntity<Object> responseEntity = restTemplate.exchange(url,HttpMethod.GET,entity, Object.class);
	Object res  = responseEntity.getBody();
	return res;
 }

• Netflix Eureka is used for discovery service.
• Netflix Ribbon is used for client side load-balancing.
• Netflix Zuul is used for gateway.

NOTE : You need to configure your own jks files for communication level security in application.properties file whereever needed.

You will build a web application that is Oauth2 enabled.

• A favorite text editor or IDE
• JDK 1.8 or later
• Gradle 4+ or Maven 3.2+

• Download and unzip the source repository for this guide, or clone it using Git: git clone https://github.com/arc-arnob/Healthe-master.git
• cd to /target folders of all the spring boot applications and run: mvnw spring-boot:run

• File Location : backend/support/jwt-auth-service/jwt_auth_service/src/main/resources/application.properties

spring.jpa.database-platform=org.hibernate.dialect.MySQL8Dialect
spring.datasource.url =jdbc:mysql://localhost:3306/<your database>
spring.datasource.username = <username>
spring.datasource.password = <password>
spring.datasource.driver-class-name = com.mysql.cj.jdbc.Driver
spring.jpa.hibernate.ddl-auto = update
spring.jpa.show-sql=true

#hibernate
#spring.jpa.generate-ddl=true
spring.jpa.hibernate.ddl-auto = update
spring.jpa.show-sql=true

• File Location : backend/core/forum/src/main/resources/application.properties

spring.jpa.database-platform=org.hibernate.dialect.MySQL8Dialect
spring.datasource.url =jdbc:mysql://localhost:3306/<Your Database>
spring.datasource.username = root
spring.datasource.password = <password>
spring.datasource.driver-class-name = com.mysql.cj.jdbc.Driver
spring.jpa.hibernate.ddl-auto = update
spring.jpa.show-sql=true

• File Location : /backend/core/gateway/src/main/resources/application.properties

spring.user.jpa.database-platform=org.hibernate.dialect
.MySQL8Dialect
spring.user.datasource.jdbcUrl= jdbc:mysql://localhost:3306/<your database>
spring.user.datasource.username = <username>
spring.user.datasource.password = <password>
spring.user.datasource.driver-class-name = com.mysql.cj.jdbc.Driver
spring.app.jpa.database-platform=org.hibernate.dialect.MySQL8Dialect
spring.app.datasource.jdbcUrl=jdbc:mysql://localhost:3306/<your database>
spring.app.datasource.username = <username>
spring.app.datasource.password = <password>
spring.app.datasource.driver-class-name = com.mysql.cj.jdbc.Driver

spring.jpa.generate-ddl=true
spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.database=default
spring.jpa.show-sql=true

• File Location : /backend/core/medicationSystem/medSystem/src/main/resources/application.properties

spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.database=<your database>
spring.data.mongodb.repositories.enabled=true
# mongod --dbpath "<path to your db>"

spring.user.jpa.database-platform=org.hibernate
.dialect.MySQL8Dialect
spring.user.datasource.jdbcUrl =jdbc:mysql://localhost:3306/<your database>
spring.user.datasource.username = <username>
spring.user.datasource.password = <password>
spring.user.datasource.driver-class-name = com.mysql.cj.jdbc.Driver

spring.jpa.generate-ddl=true
spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.database=default
spring.jpa.show-sql=true

• File Location : /backend/core/patientBooking/booking/src/main/resources/application.properties

spring.user.jpa.database-platform=org.hibernate.dialect
.MySQL8Dialectspring.user.datasource.jdbcUrl=jdbc:mysql://localhost:3306/<your database>
spring.user.datasource.username = <username>
spring.user.datasource.password = <password>
spring.user.datasource.driver-class-name = com.mysql.cj.jdbc.Driver

spring.app.jpa.database-platform=org.hibernate.dialect
.MySQL8Dialectspring.app.datasource.jdbcUrl=jdbc:mysql://localhost:3306/<your database>
spring.app.datasource.username = <username>
spring.app.datasource.password = <password>
spring.app.datasource.driver-class-name = com.mysql.cj.jdbc.Driver
spring.jpa.generate-ddl=true
spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.database=default
spring.jpa.show-sql=true

• File Location : /backend/core/storeLocator/booking_per_user/src/main/resources/application.properties

spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.database=<your database>
spring.data.mongodb.repositories.enabled=true