RPC protocol sample using a multi-language microservices flow (Java & Python).

The Architecture (E-commerce Order Flow)

• Service A (Spring Boot): Gateway / API Entry
• Service B (Spring Boot): Order Management
• Service C (Python FastAPI): Inventory Service
• Service D (Spring Boot): Notification Service

---

To install python rpc dependencies

pip install grpcio grpcio-tools        

To convert proto files for python

python -m grpc_tools.protoc -I. --python_out=. --grpc_python_out=. inventory.proto

Sample usage

python -m grpc_tools.protoc -I. --python_out=inventory_service\ --grpc_python_out=inventory_service\ protos\inventory.proto 

To run python service in the project

python -m inventory_service.app.inventory_server

Java RPC Server dependency

<dependency>
    <groupId>net.devh</groupId>
    <artifactId>grpc-server-spring-boot-starter</artifactId>
    <version>2.15.0.RELEASE</version>
</dependency>

Java RPC Client dependency

<dependency>
    <groupId>net.devh</groupId>
    <artifactId>grpc-client-spring-boot-starter</artifactId>
    <version>2.15.0.RELEASE</version>
</dependency>

Java proto files conversion / code generation

The process has a plugin to generate RPC dependencies and Request and Response objects as defined in .proto files

<plugin>
    <groupId>org.xolstice.maven.plugins</groupId>
    <artifactId>protobuf-maven-plugin</artifactId>
    <version>0.6.1</version>
    <configuration>
        <protocArtifact>com.google.protobuf:protoc:3.24.0:exe:${os.detected.classifier}</protocArtifact>
        <pluginId>grpc-java</pluginId>
        <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.58.0:exe:${os.detected.classifier}</pluginArtifact>

        <protoSourceRoot>../protos</protoSourceRoot>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>compile</goal>
                <goal>compile-custom</goal>
            </goals>
        </execution>
    </executions>
</plugin>

Default plugin will look for .proto files at src/main/proto if using different path configure with protoSourceRoot tag.

To generate code from proto compile the project. The code will be generated in target.

TIP: To recognize these as dependencies in IntelliJ mark target/generated-sources/grpc-java and target/generated-sources/java as Generated Sources Root

---

• RPC serve which is running in Java or Python will not interfere with other Server or process What that mean ?

  • I can still run my regular spring boot application on port 8080 and my RPC server on 9090. Similarly in python i can run FastAPI server and RPC server at the same time on different port.

Open Question ?

• How dose the network pool will be configured. As in Spring boot and RPC will share the network bandwidth ?
  • Ans -> will be different because gRPC will spin up new netty connection threads/pool so it will not interfere with Spring Web/Spring Flux server. Bandwidth is same as serving on same host but port will be different.

Docker

Build docker images

docker build -t service-a -f service-A/Dockerfile . && docker build -t service-b -f service-B/Dockerfile . && docker build -t service-c -f service_C/Dockerfile . && docker build -t service-d -f service-D/Dockerfile .

How to run it: Start everything:

docker-compose up

(Add -d at the end if you want it to run in the background)

Check logs: If something isn't working, check the logs of a specific service:

docker-compose logs -f service-a

Stop everything:

docker-compose down