baobab/reference_jsonrpsee_crate_examples/ws_pubsub_broadcast.rs

// Copyright 2019-2021 Parity Technologies (UK) Ltd.
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//! Example that shows how to broadcast to all active subscriptions using `tokio::sync::broadcast`.

use std::net::SocketAddr;

use futures::StreamExt;
use futures::future::{self, Either};
use jsonrpsee::PendingSubscriptionSink;
use jsonrpsee::core::client::{Subscription, SubscriptionClientT};
use jsonrpsee::core::middleware::RpcServiceBuilder;
use jsonrpsee::rpc_params;
use jsonrpsee::server::{RpcModule, Server, ServerConfig};
use jsonrpsee::ws_client::WsClientBuilder;
use tokio::sync::broadcast;
use tokio_stream::wrappers::BroadcastStream;

const NUM_SUBSCRIPTION_RESPONSES: usize = 5;

#[tokio::main]
async fn main() -> anyhow::Result<()> {
	tracing_subscriber::FmtSubscriber::builder()
		.with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
		.try_init()
		.expect("setting default subscriber failed");

	let addr = run_server().await?;
	let url = format!("ws://{}", addr);

	let client1 =
		WsClientBuilder::default().set_rpc_middleware(RpcServiceBuilder::new().rpc_logger(1024)).build(&url).await?;
	let client2 =
		WsClientBuilder::default().set_rpc_middleware(RpcServiceBuilder::new().rpc_logger(1024)).build(&url).await?;
	let sub1: Subscription<i32> = client1.subscribe("subscribe_hello", rpc_params![], "unsubscribe_hello").await?;
	let sub2: Subscription<i32> = client2.subscribe("subscribe_hello", rpc_params![], "unsubscribe_hello").await?;

	let fut1 = sub1.take(NUM_SUBSCRIPTION_RESPONSES).for_each(|r| async move { tracing::info!("sub1 rx: {:?}", r) });
	let fut2 = sub2.take(NUM_SUBSCRIPTION_RESPONSES).for_each(|r| async move { tracing::info!("sub2 rx: {:?}", r) });

	future::join(fut1, fut2).await;

	Ok(())
}

async fn run_server() -> anyhow::Result<SocketAddr> {
	// let's configure the server only hold 5 messages in memory.
	let config = ServerConfig::builder().set_message_buffer_capacity(5).build();
	let server = Server::builder()
		.set_config(config)
		.set_rpc_middleware(RpcServiceBuilder::new().rpc_logger(1024))
		.build("127.0.0.1:0")
		.await?;
	let (tx, _rx) = broadcast::channel::<usize>(16);

	let mut module = RpcModule::new(tx.clone());

	std::thread::spawn(move || produce_items(tx));

	module
		.register_subscription("subscribe_hello", "s_hello", "unsubscribe_hello", |_, pending, tx, _| async move {
			let rx = tx.subscribe();
			let stream = BroadcastStream::new(rx);
			pipe_from_stream_with_bounded_buffer(pending, stream).await?;
			Ok(())
		})
		.unwrap();
	let addr = server.local_addr()?;
	let handle = server.start(module);

	// In this example we don't care about doing shutdown so let's it run forever.
	// You may use the `ServerHandle` to shut it down or manage it yourself.
	tokio::spawn(handle.stopped());

	Ok(addr)
}

async fn pipe_from_stream_with_bounded_buffer(
	pending: PendingSubscriptionSink,
	stream: BroadcastStream<usize>,
) -> Result<(), anyhow::Error> {
	let sink = pending.accept().await?;
	let closed = sink.closed();

	futures::pin_mut!(closed, stream);

	loop {
		match future::select(closed, stream.next()).await {
			// subscription closed.
			Either::Left((_, _)) => break Ok(()),

			// received new item from the stream.
			Either::Right((Some(Ok(item)), c)) => {
				let msg = serde_json::value::to_raw_value(&item)?;

				// NOTE: this will block until there a spot in the queue
				// and you might want to do something smarter if it's
				// critical that "the most recent item" must be sent when it is produced.
				if sink.send(msg).await.is_err() {
					break Ok(());
				}

				closed = c;
			}

			// Send back back the error.
			Either::Right((Some(Err(e)), _)) => break Err(e.into()),

			// Stream is closed.
			Either::Right((None, _)) => break Ok(()),
		}
	}
}

// Naive example that broadcasts the produced values to all active subscribers.
fn produce_items(tx: broadcast::Sender<usize>) {
	for c in 1..=100 {
		std::thread::sleep(std::time::Duration::from_millis(1));

		// This might fail if no receivers are alive, could occur if no subscriptions are active...
		// Also be aware that this will succeed when at least one receiver is alive
		// Thus, clients connecting at different point in time will not receive
		// the items sent before the subscription got established.
		let _ = tx.send(c);
	}
}