alexnika/2026-02-otus-microservices-nikolaev

Scope and Evolution

This is an OTUS Microservice Architecture course repository organized as incremental assignments (hw01–hw07). Early modules demonstrate a standalone Spring Boot HTTP service and Kubernetes deployment; hw04–hw06 evolve it into a PostgreSQL-backed, monitored, JWT-secured user service. hw07 is the architectural culmination: a multi-service order/billing/notification system.

Primary Entry Points

The deployable runtime units in hw07 are independent Java/Spring Boot applications:

• User/authentication service: hw07/USERService/src/main/java/ru/otus/hw/UserServiceApplication.java

• Order service: hw07/ORDERService/src/main/java/ru/otus/hw/OrderServiceApplication.java

• Billing service: hw07/BILLINGService/src/main/java/ru/otus/hw/BillingServiceApplication.java

• Notification service: hw07/NOTIFICATIONService/src/main/java/ru/otus/hw/NotificationServiceApplication.java

The root Gradle build defines the multi-module project at hw07/build.gradle and hw07/settings.gradle. Local composition is represented by hw07/DEV/docker-compose.yaml; Kubernetes deployment is packaged as hw07/hw07chart.

User and Identity Boundary

USERService owns users, profiles, roles, credential handling, and JWT issuance/validation. Its REST resources split authentication, role administration, user CRUD, and profile operations:

• hw07/USERService/src/main/java/ru/otus/hw/controller/AuthResource.java

• hw07/USERService/src/main/java/ru/otus/hw/controller/UserResource.java

• hw07/USERService/src/main/java/ru/otus/hw/security/JwtAuthenticationFilter.java

JWT security and BCrypt configuration form the external-client authorization boundary. User registration/service behavior can call Billing through hw07/USERService/src/main/java/ru/otus/hw/client/BillingServiceClient.java, likely establishing an account as part of user lifecycle. User data has dedicated Flyway migrations under hw07/USERService/src/main/resources/db/migration.

Order Processing and Synchronous Billing

ORDERService owns order persistence and the public order API:

• hw07/ORDERService/src/main/java/ru/otus/hw/controller/OrderResource.java

• hw07/ORDERService/src/main/java/ru/otus/hw/service/OrderServiceImpl.java

• hw07/ORDERService/src/main/java/ru/otus/hw/models/Order.java

Order creation flows through the service layer to its database, then uses BillingServiceClient for synchronous billing operations (hw07/ORDERService/src/main/java/ru/otus/hw/client/BillingServiceClient.java). This is a direct service-to-service boundary configured via REST-client and billing-URL configuration.

Billing and Internal API Boundary

BILLINGService owns accounts and transaction records:

• hw07/BILLINGService/src/main/java/ru/otus/hw/controller/AccountResource.java

• hw07/BILLINGService/src/main/java/ru/otus/hw/controller/InternalAccountResource.java

• hw07/BILLINGService/src/main/java/ru/otus/hw/service/TransactionServiceImpl.java

It exposes both account-facing and internal account/order resources. InternalApiFilterConfig in billing and order services indicates protected internal calls using an API-key boundary:

• hw07/BILLINGService/src/main/java/ru/otus/hw/config/InternalApiFilterConfig.java

• hw07/ORDERService/src/main/java/ru/otus/hw/config/InternalApiFilterConfig.java

Account and transaction schemas are independently migrated in hw07/BILLINGService/src/main/resources/db/migration.

Asynchronous Notification Pipeline

After order activity, ORDERService publishes a shared notification event through RabbitMQ:

• hw07/ORDERService/src/main/java/ru/otus/hw/producer/NotificationEventPublisher.java

• hw07/COMMONDomain/src/main/java/ru/otus/hw/dto/NotificationEvent.java

NOTIFICATIONService consumes that event, persists notifications, and exposes a notification API:

• hw07/NOTIFICATIONService/src/main/java/ru/otus/hw/consumer/NotificationConsumer.java

• hw07/NOTIFICATIONService/src/main/java/ru/otus/hw/service/NotificationServiceImpl.java

• hw07/NOTIFICATIONService/src/main/java/ru/otus/hw/config/RabbitMQListenerConfig.java

This separates notification delivery from the synchronous order/billing path. COMMONDomain is the explicit shared contract module for cross-service DTOs, errors, and common entity abstractions.

Infrastructure and Operations

Each service has its own Dockerfile and application configuration, while the Helm chart provisions application deployments/services, PostgreSQL stateful infrastructure, RabbitMQ, secrets/configuration, and ingress:

• hw07/hw07chart/templates/app-deployment.yaml

• hw07/hw07chart/templates/postgres-statefulset.yaml

• hw07/hw07chart/templates/rabbitmq.yaml

Earlier hw05 adds Prometheus/Grafana deployment assets, including service monitors and a PostgreSQL exporter, under hw05/prometheus-grafana-chart. The principal material runtimes are Java/Spring Boot, Gradle (final multi-service module), PostgreSQL with Flyway migrations, RabbitMQ, Docker, Kubernetes/Helm, and NGINX Ingress.