gRPC is a modern opensource high performance RPC framework initially developed by google . It is language independent and can run in any environments. gRPC build on top of HTTP 2 and Protocol Buffers.

HTTP 2

HTTP is improved version of HTTP 1.1 and efficiently uses single TCP connection with multiplexing.

Protocol buffers

gRPC uses protocol buffers to transport data between client and server. This provides template kind of structure to generate the code in any language.

service HelloService {
  rpc SayHello (HelloRequest) returns (HelloResponse);
}
message HelloRequest {
  string greeting = 1;
}
message HelloResponse {
  string reply = 1;
}

Types of communication

Nature of the gRPC communication is asynchronous. There are four types of RPC Life cycle

• Unary
• Client streaming
• Server streaming
• Bi-directional streaming

Project setup

At very first stage a java project needs to be created to test grpc functionality. New project can be created using Maven (command line or using any IDE).

To generate a project navigate, navigate to the folder you want to create in terminal or command prompt and type this command.

mvn archetype:generate 
	-DgroupId=com.thebytecloud 
	-DartifactId=grpc-java-examples 
	-DarchetypeArtifactId=maven-archetype-quickstart 
	-DinteractiveMode=false

update the pom with below dependency.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.thebytecloud</groupId>
    <artifactId>grpc-java-examples</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>3.6.1</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-netty-shaded</artifactId>
            <version>1.15.1</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-protobuf</artifactId>
            <version>1.15.1</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-stub</artifactId>
            <version>1.15.1</version>
        </dependency>
    </dependencies>
    <build>
        <defaultGoal>clean generate-sources compile install</defaultGoal>
        <plugins>
            <!-- compile proto file into java files. -->
            <plugin>
                <groupId>com.github.os72</groupId>
                <artifactId>protoc-jar-maven-plugin</artifactId>
                <version>3.6.0.1</version>
                <executions>
                    <execution>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>run</goal>
                        </goals>
                        <configuration>
                            <includeMavenTypes>direct</includeMavenTypes>
                            <inputDirectories>
                                <include>src/main/resources</include>
                            </inputDirectories>
                            <outputTargets>
                                <outputTarget>
                                    <type>java</type>
                                    <outputDirectory>src/main/java</outputDirectory>
                                </outputTarget>
                                <outputTarget>
                                    <type>grpc-java</type>
                                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.15.0</pluginArtifact>
                                    <outputDirectory>src/main/java</outputDirectory>
                                </outputTarget>
                            </outputTargets>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.0</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>