Audiobook Platform

A microservices backend for an audiobook streaming platform, supporting on-demand audio playback, live broadcasts, in-app purchases, and full-text search. Built on Spring Cloud with event-driven communication and horizontally-scalable services.

Architecture

Ten domain-aligned microservices behind an API gateway, communicating over both synchronous (HTTP/REST) and asynchronous (Kafka) channels. Each service owns its database; cross-service queries go through declarative REST clients with circuit-breaker protection.

                      ┌──────────────┐
   clients ─────────► │ API Gateway  │  routing · CORS · rate limit
                      └──────┬───────┘
                             │
   ┌─────────────────────────┼─────────────────────────┐
   │                         │                         │
┌──▼──┐ ┌──────┐ ┌──────┐ ┌──▼──┐ ┌──────┐ ┌──────┐ ┌──▼──┐
│User │ │Album │ │Order │ │Pay  │ │Search│ │Live  │ │ ... │
└──┬──┘ └──┬───┘ └──┬───┘ └──┬──┘ └──┬───┘ └──┬───┘ └─────┘
   │       │        │        │       │        │
   └───────┴────────┴────────┴───────┴────────┘
            Kafka (events) · Redis (cache/locks)
            MySQL · MongoDB · Elasticsearch · Object Storage

Services

Service	Port	Responsibility
server-gateway	8500	API gateway, routing, CORS, global rate limiting
service-album	8501	Albums, tracks, audio upload pipeline
service-user	8503	User profiles, OAuth2 login, listening history
service-order	8504	Order lifecycle, inventory, idempotent state machine
service-account	8505	User wallet, virtual currency, transactions
service-payment	8506	Payment gateway integration, webhook verification
service-live	8507	Live streaming (RTMP ingest / HLS playback), WebSocket chat
service-comment	8508	Comments and replies (MongoDB)
service-dispatch	8509	Distributed scheduled jobs (indexing, expiry sweeps)
service-search	8502	Full-text search over albums and tracks
service-system	8510	Admin/back-office APIs

Tech Stack

Core

• Java 17, Spring Boot 3.0.5, Spring Cloud 2022.0.2
• Spring Cloud Gateway — API gateway
• OpenFeign — declarative REST clients between services
• Service discovery & centralized configuration (via Nacos)
• Circuit breaker, rate limiting, and flow control (via Sentinel)

Data

• MySQL 8 + MyBatis-Plus — relational persistence (per-service databases)
• Redis + Redisson — caching, distributed locks, rate limiters
• MongoDB — comments and other semi-structured data
• Elasticsearch — full-text search and ranking

Async & Scheduling

• Apache Kafka — event-driven communication (order events, search indexing, listening history)
• XXL-Job — distributed task scheduling for batch jobs and timeouts

Media & Storage

• S3-compatible object storage (MinIO) — audio file storage
• Video-on-demand pipeline — transcoding, signed playback URLs, CDN delivery
• Live streaming — RTMP ingest, HLS playback, real-time chat over WebSocket

Integrations

• OAuth2-based third-party login — token exchange, signed JWTs
• Payment gateway integration — signed webhook callbacks, idempotency keys, refund flow

API & Tooling

• OpenAPI 3 / Swagger — interactive API documentation
• Jackson — JSON serialization
• HikariCP — connection pooling

Key Engineering Features

• Idempotent payment flow — webhook signature verification, deduplication via Redis, automatic retries with exponential backoff
• Event-driven order pipeline — order placement, payment confirmation, and inventory adjustments coordinated through Kafka topics
• Distributed locks — Redisson-backed locks guard inventory deduction and seckill flows under concurrent load
• Read-through caching — frequently accessed album/track data cached in Redis with explicit invalidation on writes
• Async search indexing — album mutations publish to Kafka; the search service consumes and indexes into Elasticsearch, decoupling write paths from search availability
• Signed playback URLs — short-lived signed URLs prevent unauthorized audio/video access

Project Structure

.
├── common/             Shared utilities (logging, Kafka helpers, security, etc.)
├── model/              Cross-service DTOs / VOs / entities
├── server-gateway/     Spring Cloud Gateway
├── service/            Business microservices (album, user, order, ...)
├── service-client/     Feign client interfaces for inter-service calls
└── Resource/           Nacos config templates (DEFAULT_GROUP/*.yaml)

Prerequisites

• JDK 17
• Maven 3.6+
• MySQL 8.x
• Redis
• Nacos Server (for service discovery and config)
• Apache Kafka
• MongoDB
• Elasticsearch 7.x+
• MinIO (or any S3-compatible object store)
• XXL-Job admin (optional, for scheduled jobs)

Install pinyin4j into your local Maven repo before building:

mvn install:install-file \
  -Dfile=/path/to/pinyin4j-2.5.0.jar \
  -DgroupId=com.belerweb \
  -DartifactId=pinyin4j \
  -Dversion=2.5.0 \
  -Dpackaging=jar

Configuration

All service configs are loaded from Nacos at startup. Templates live under Resource/DEFAULT_GROUP/ with <PLACEHOLDER> tokens — fill them in with your own credentials and import into your Nacos DEFAULT_GROUP namespace before starting services.

Note: Do not commit real credentials. The templates intentionally use placeholders for database passwords, third-party API keys, and host names.

Build & Run

# Build all modules
mvn clean install -DskipTests

# Start the gateway, then each service
cd server-gateway && mvn spring-boot:run
cd service/service-user && mvn spring-boot:run
# ... etc

Each service is an independent Spring Boot application; run only the services you need for local development.

API Documentation

Once a service is running, interactive OpenAPI docs are available at:

http://<host>:<service-port>/doc.html