GO-TO-SCHOOL

####There is an example for SpringBoot Micro-services

Service Raw Information

1. Discovery Service: using Eureka Service for exploring child services
2. Gateway Service: using Spring Cloud Gateway for routing
3. Auth Service: using OAuth2 protocol. It contains model `User`. Username & Password for login
4. Core Service: It contains models: `Student`, `Teacher`, `Classroom`. A student / teacher is only in one classroom. A classroom has many students, one teacher.
5. Report Service: Make reports about Classroom
6. Logger Service: log result from `Report Service`. Using kafka to handle event
7. UI Service: display data. Using ReactJs.

Explain:
- At start-time, all services will register themself to discovery-service.
1. Request to system, it goes through gateway-service
2 & 3. Gateway-service fetches public_key from auth-service via rest api for authenticate & authorize. If success, request goes to destination, else reject with code 401 or 403.
4. Request goes to service destination for business via Rest API
5. If request comes report-service, report-service will contact core-service via Rest & gRPC.
6. After report-service processes request successfully, it pushes one message to kafka-server
7. Logger-service receives message from kafka-server

Setup

I. Install Kafka for event streaming

• Download & install kafka:
  • If Os is Windows, follow: https://www.geeksforgeeks.org/how-to-install-and-run-apache-kafka-on-windows/
  • Another Os, follow: https://kafka.apache.org/quickstart
• Zookeeper starts at port: 2181
• Kafka starts at port: 9092

II. Install postgres database

• Download & install: https://www.postgresql.org/download/
• Setting username & password. Default username: postgres
• Postgres starts at port: 5432
• Create database for gts-core-service: gts_core, gts_auth

III. JDK

• Require JDK 11+

IV. Gradle

• If use IntelIJ IDEA, skip this step. IntelIJ supports to build spring-native package for GraalVM
• Install Gradle follow guideline at here: https://www.tutorialspoint.com/gradle/gradle_installation.htm

V. Docker

• if on local, recommend to use Docker Desktop
• Install docker by using google-search

Microservices

Please run all services by below ordered. All services can be built into native-image by spring-native

I. Common-lib

• Module name: gts-common-lib
• Contain base package for another services: annotation, constant, dto, exception, util, protobuf
• Using google.protobuf lib to convert .proto file to .java file
• This module is compiled with another modules

II. Discovery-service

• Module name: gts-discovery-service
• Using eureka-server for exploring child services
• Service starts at fixed port: 8761
• View all registered services at local: http://localhost:8711
• Run DiscoveryApplication.java to start service

III. Gateway-service

• Module name: gts-gateway-service
• Using spring-cloud-gateway
• Service starts at fixed port: 8080
• Info: all requests will be authenticated at gateway, before coming to destination service
• Run GatewayApplication.java to start service

IV. Auth-service

• Module name: gts-auth-service
• Info: Apply OAuth2 with Jwt for authentication
• Service starts at fixed port: 8000
• Change DB config at application.properties
• Add postman guideline for auth-service to view at here: https://h.readthedocs.io/en/latest/api/authorization/#client-credentials
• Springboot support 3 ways for tokenStore
  • InMemoryTokenStore: AccessToken is stored in ConcurrentHashMap(memory). No use for distributed system because sync.
  • JdbcTokenStore: AccessToken is stored in DB
  • RedisTokenStore: AccessToken is stored in redis server
  • JwtTokenStore: Authorizaton Server doesn't store AccessToken. Using public key for validating. So, Jwt is invalid when it is expired. Please set short-time for it.
• Running:
  • POST /oauth/token: for login. Body request: grant_type: password, username, password
  • GET /oauth/check_token?token=...
  • POST /oauth/token: check token. Body request: grant_type: refresh_token, username, password, refresh_token
  • Running AuthApplication.java to start service

V. Core-service

• Module name: gts-core-service
• Info: Process main business logic for teacher, student, classroom
• Support REST API & gRPC
• Change DB config at application.properties
• Tomcat server & gRPC server starts at dynamic port, the port will be determined at runtime
• View Open API specification at: http://localhost:<port>/core/swagger-ui/index.html
• Running:
  • Run CoreApplication.java to start service
  • Test API: http://localhost:<port>/core/api/v1/hello (if run through gateway, please set <port> to 8080)
  • Test gRPC: Using Postman, choose gRPC request. Set server URL: http://localhost:<port>. Choose classroom.proto (in common-lib). Select valid method. Finally, click Invoke

VI. Report-service

• Module name: gts-report-service
• Info: Connect to gts-core-service to provide report through rest apis
• Report-service connect Core-service by using RestAPI & gRPC
• When client call apis to get report, there are message as action log sent to kafka
• Apply SpringBatch to clear ServiceInstanceCache: run every 5 minutes.
  • SpringBatch flow:
    • Create Tasklet -> add it to Step -> Add to Job. Using JobLaucher to run job.
    • Push JobLaucher & Jobto JobDetail -> Add to Trigger with one scheduler -> Running.
    • Can use Reader, Processor, Writer flow for JDBC working.
    • View detail at: https://docs.spring.io/spring-batch/docs/current/reference/html/readersAndWriters.html
• Running:
  • Need start Core-service & Kafka (view setup step) at first
  • Run ReportApplication.java to start service
  • Start a kafka consumer on the terminal. Read the events from topic report-logger (view setup step for get detail)
  • Test API: http://localhost:<port>/core/api/v1/report/student (if run through gateway, please set <port> to 8080)

VII. Logger-service

• Module name: gts-logger-service
• Info: Receive messages from report-service via kafka and then, show them on console.
• Running:
  • Start Kafka & Core-service & Report-service at first
  • Run LoggerApplication.java to start service
  • Make an API caller to Report-service. And then, view logger-service's console to see event message.

Build & Run all services

• Running by docker (easily way):

  • Turn on docker app
  • Go to project_path, run command: ./docker-native.sh
  • Source code will be packed into native-image

• Running by jar file:

  • Run command: ./gradlew :<service_name>:build

    ex: ./gradlew :auth-service:build

  • Go to build_folder inside service and run command: java -jar <service_name>.jar

    ex: java -jar gts-auth-service.jar

  • Remember DB setting before start service by above guideline.

• Test:

  • Using postman, view all services: http://localhost:8761 (may be take time, please refresh page)
  • You need login at first, authentication info: use grant_type: password and username,password,client_id,client_secret at here
  • You can use postman collection for import to Postman app, at here
  • Enjoy result ^^

TODO

• Add caching for GET API or Get data from DB by using Redis
• Add cloud-load-balancer dependence for call api from report service to core service
• Create external service, impl SSO to follow: https://shekhargulati.com/2018/02/15/single-sign-on-in-spring-boot-applications-with-spring-security-oauth
• Add system architecture image
• Add websocket
• Add prometheus
• Add circus breaker