server.rs

use tonic::{
    transport::{RequestExt, Server},
    Request, Response, Status,
};

use hello_world::greeter_server::{Greeter, GreeterServer};
use hello_world::{HelloReply, HelloRequest};
use std::time::Duration;
use tonic_health::server::HealthReporter;

pub mod hello_world {
    tonic::include_proto!("helloworld");
}

#[derive(Default)]
pub struct MyGreeter {}

#[tonic::async_trait]
impl Greeter for MyGreeter {
    async fn say_hello(
        &self,
        request: Request<HelloRequest>,
    ) -> Result<Response<HelloReply>, Status> {
        println!("Got a request from {:?}", request.remote_addr());

        let reply = hello_world::HelloReply {
            message: format!("Hello {}!", request.into_inner().name),
        };
        Ok(Response::new(reply))
    }
}

/// This function (somewhat improbably) flips the status of a service every second, in order
/// that the effect of `tonic_health::HealthReporter::watch` can be easily observed.
async fn twiddle_service_status(mut reporter: HealthReporter) {
    let mut iter = 0u64;
    loop {
        iter += 1;
        tokio::time::sleep(Duration::from_secs(1)).await;

        if iter % 2 == 0 {
            reporter.set_serving::<GreeterServer<MyGreeter>>().await;
        } else {
            reporter.set_not_serving::<GreeterServer<MyGreeter>>().await;
        };
    }
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (mut health_reporter, health_service) = tonic_health::server::health_reporter();
    health_reporter
        .set_serving::<GreeterServer<MyGreeter>>()
        .await;

    tokio::spawn(twiddle_service_status(health_reporter.clone()));

    let addr = "[::1]:50051".parse().unwrap();
    let greeter = MyGreeter::default();

    println!("HealthServer + GreeterServer listening on {}", addr);

    Server::builder()
        .add_service(health_service)
        .add_service(GreeterServer::new(greeter))
        .serve(addr)
        .await?;

    Ok(())
}