rest-sample-dubbo-provider

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A plain Java Dubbo provider used by the Rust-Java REST consumer sample.

• It does not use Spring Boot.
• It can run without ZooKeeper.
• It can register itself in ZooKeeper.
• It can serve ready JSON or typed records.
• The full profile uses PostgreSQL and HikariCP.

Current versions: java-rust-dubbo:0.5.0, rest-sample-utility:0.3.0, rust-sample-model:0.3.0.

Start Here

Choose one provider shape.

Need	Maven profile	Includes
Small ready-JSON catalog provider	catalog-static-provider	One catalog interface; no DB and no ZooKeeper
Read-only PostgreSQL provider	db-query-provider	Customer queries and HikariCP; no commands
Catalog, queries, and commands	full-provider	Full sample; active by default

Do not package the full provider when the service only needs one catalog method. The smaller profile loads fewer classes and uses less memory.

Quick Start

Option A: Small catalog provider

Run from this repository:

$env:GITHUB_PACKAGES_TOKEN="YOUR_TOKEN_WITH_READ_PACKAGES"

mvn -q -Pcatalog-static-provider clean package

java `
  "-Ddubbo.provider.host=127.0.0.1" `
  "-Ddubbo.provider.bind-host=127.0.0.1" `
  "-Ddubbo.provider.port=20880" `
  "-Dreactor.dubbo.registry-enabled=false" `
  -jar target/rest-sample-dubbo-provider-0.4.0.jar

Use it with the consumer's native-static-consumer profile.

Option B: Full provider with PostgreSQL

Start PostgreSQL:

docker rm -f rs-provider-postgres-test 2>$null

docker run -d --name rs-provider-postgres-test `
  -e POSTGRES_DB=reactor_sample `
  -e POSTGRES_USER=reactor `
  -e POSTGRES_PASSWORD=reactor `
  -p 15432:5432 postgres:16-alpine

Build and start the provider:

$env:GITHUB_PACKAGES_TOKEN="YOUR_TOKEN_WITH_READ_PACKAGES"

mvn -q clean package

java `
  "-Dreactor.dubbo.registry-enabled=false" `
  "-Dsample.db.jdbc-url=jdbc:postgresql://127.0.0.1:15432/reactor_sample" `
  "-Dsample.db.username=reactor" `
  "-Dsample.db.password=reactor" `
  "-Dsample.db.schema-init=true" `
  "-Dsample.db.warmup=true" `
  -jar target/rest-sample-dubbo-provider-0.4.0.jar

The provider listens on 127.0.0.1:20880.

Start the consumer with:

sample.dubbo.discovery=static
reactor.dubbo.providers=127.0.0.1:20880

What the Provider Exposes

The provider does not expose HTTP endpoints. It exports Dubbo interfaces.

Interface	Example methods	Data shape
CatalogJsonService	getNestedCatalogJson()	Ready JSON byte[]
NestedCatalogService	title, count, info, item list, attributes	String, primitive, record, list, map
CustomerQueryService	customer, segment list, stats, exists	Ready JSON and typed results
CustomerCommandService	create, patch, delete	JSON bytes and typed command records

The shared interface package must stay com.reactor.rust.dubbo.sample. Dubbo uses the full interface name as the service identity.

Static Address or ZooKeeper?

Without ZooKeeper

Use this when the consumer reaches the provider through a known address or Kubernetes Service DNS.

reactor.dubbo.registry-enabled=false
dubbo.provider.bind-host=0.0.0.0
dubbo.provider.port=20880

Kubernetes example:

rest-sample-dubbo-provider:20880

The Service can point to one or many provider pods.

With ZooKeeper

Use this when the provider must register itself in a Dubbo registry.

reactor.dubbo.registry-enabled=true
reactor.dubbo.registry-address=zookeeper://zookeeper-client.platform.svc.cluster.local:2181
reactor.dubbo.registry-root=dubbo

ZooKeeper is optional. Do not enable it only because the provider uses Dubbo.

Database and Concurrency Limits

The default production shape is intentionally small:

sample.db.maximum-pool-size=2
sample.db.minimum-idle=0

dubbo.provider.executor.core-threads=1
dubbo.provider.executor.max-threads=8
dubbo.provider.executor.queue-capacity=16

dubbo.provider.service.CustomerQueryService.max-concurrent=2
dubbo.provider.service.CustomerCommandService.max-concurrent=2
dubbo.provider.service.CustomerCommandService.method.patchCustomerStatus.max-concurrent=1

Why:

1. HikariCP has two database connections.
2. Query and command concurrency stays close to real DB capacity.
3. Same-row updates run one at a time.
4. A bounded queue prevents unlimited memory growth.

Increase the DB pool and service limits together. First check PostgreSQL CPU, connection count, lock wait, and query latency.

Do not increase only the queue. That delays failures and usually slows the worst requests.

JSON and DTO Choice

Need	Provider return type	Result
Consumer forwards JSON without reading fields	byte[] containing UTF-8 JSON	Creates the fewest Java objects
Consumer needs one value	Primitive or String	Small typed contract
Consumer makes business decisions	Small immutable record	Clear contract with Hessian decode cost
Consumer forwards a large page	Ready JSON byte[]	Avoids a large record/list graph

Typed DTO packages must be present on both sides and allowed by Hessian security:

src/main/resources/security/serialize.allowlist

Configuration

The application reads configuration in this order:

1. src/main/resources/rest-sample-dubbo-provider.properties
2. Files passed through reactor.config.file or REACTOR_CONFIG_FILE
3. JVM -D... values and supported environment variables

File	Purpose
rest-sample-dubbo-provider.properties	Local provider, registry, service limit, and DB defaults
config/production.properties	Kubernetes bind address and low-memory HikariCP defaults
config/advanced-tuning.properties	Per-method limits and Netty/Dubbo memory controls

Production should run database migrations outside this process:

sample.db.schema-init=false

The sample sets it to true only for an easy local start.

Container Images

Image definition	Use
docker/images/Dockerfile.jlink.catalog-static	Small catalog-only provider
docker/images/Dockerfile.jlink.db-query	PostgreSQL query-only provider
docker/images/Dockerfile.jlink	Full provider
docker/images/Dockerfile	Full Docker Compose provider

See docker/images/README.md before building a jlink image. Container builds also need Maven access to the private shared packages.

Code Map

File	Why it matters
RestSampleDubboProviderApplication.java	Starts the full provider
CatalogStaticProviderApplication.java	Starts the catalog-only provider
DbQueryOnlyProviderApplication.java	Starts the DB query-only provider
*ProviderModule.java	Declares exported services
CustomerQueryServiceImpl.java	DB read examples
CustomerCommandServiceImpl.java	DB command examples
PostgresCustomerRepository.java	SQL, transaction, and paging logic
rest-sample-dubbo-provider.properties	Local settings

Maven Package Access

GitHub Packages requires a token with read:packages. The token also needs access to the private shared sample repositories.

The server IDs in ~/.m2/settings.xml must match the POM:

<servers>
  <server>
    <id>github-java-rust-dubbo</id>
    <username>YOUR_GITHUB_USERNAME</username>
    <password>${env.GITHUB_PACKAGES_TOKEN}</password>
  </server>
  <server>
    <id>github-rest-sample-utility</id>
    <username>YOUR_GITHUB_USERNAME</username>
    <password>${env.GITHUB_PACKAGES_TOKEN}</password>
  </server>
  <server>
    <id>github-rust-sample-model</id>
    <username>YOUR_GITHUB_USERNAME</username>
    <password>${env.GITHUB_PACKAGES_TOKEN}</password>
  </server>
</servers>

Common Problems

Symptom	Check
Maven returns 401	Token, private repo access, and all server IDs
Port 20880 is unavailable	Another provider or container already uses it
Consumer cannot connect	Bind host, advertised host, port, Service DNS, and firewall
PostgreSQL connection fails	JDBC URL, 15432 port, username, and password
Typed DTO is rejected	Shared model version and serialize.allowlist
Some write requests are much slower	DB lock wait, Hikari pool wait, method limit, and same-row contention

More Detail

• Turkish user guide
• Turkish PDF guide
• Docker runbook
• Production settings
• Advanced tuning
• v0.4.0 release notes