Updates

reference_jsonrpsee_crate_examples/client_subscription_drop_oldest_item.rs

@@ -0,0 +1,127 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any
+// person obtaining a copy of this software and associated
+// documentation files (the "Software"), to deal in the
+// Software without restriction, including without
+// limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of
+// the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice
+// shall be included in all copies or substantial portions
+// of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+use std::net::SocketAddr;
+use std::time::Duration;
+
+use futures::{Stream, StreamExt};
+use jsonrpsee::core::DeserializeOwned;
+use jsonrpsee::core::client::{Subscription, SubscriptionClientT};
+use jsonrpsee::rpc_params;
+use jsonrpsee::server::{RpcModule, Server};
+use jsonrpsee::ws_client::WsClientBuilder;
+use tokio_stream::wrappers::BroadcastStream;
+use tokio_stream::wrappers::errors::BroadcastStreamRecvError;
+
+#[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 client = WsClientBuilder::default().build(&url).await?;
+
+	let sub: Subscription<i32> = client.subscribe("subscribe_hello", rpc_params![], "unsubscribe_hello").await?;
+
+	// drop oldest messages from subscription:
+	let mut sub = drop_oldest_when_lagging(sub, 10);
+
+	// Simulate that polling takes a long time.
+	tokio::time::sleep(Duration::from_secs(1)).await;
+
+	// The subscription starts from zero but you can
+	// notice that many items have been replaced
+	// because the subscription wasn't polled.
+	for _ in 0..10 {
+		match sub.next().await.unwrap() {
+			Ok(n) => {
+				tracing::info!("recv={n}");
+			}
+			Err(e) => {
+				tracing::info!("{e}");
+			}
+		};
+	}
+
+	Ok(())
+}
+
+fn drop_oldest_when_lagging<T: Clone + DeserializeOwned + Send + Sync + 'static>(
+	mut sub: Subscription<T>,
+	buffer_size: usize,
+) -> impl Stream<Item = Result<T, BroadcastStreamRecvError>> {
+	let (tx, rx) = tokio::sync::broadcast::channel(buffer_size);
+
+	tokio::spawn(async move {
+		// Poll the subscription which ignores errors.
+		while let Some(n) = sub.next().await {
+			let msg = match n {
+				Ok(msg) => msg,
+				Err(e) => {
+					tracing::error!("Failed to decode the subscription message: {e}");
+					continue;
+				}
+			};
+
+			if tx.send(msg).is_err() {
+				return;
+			}
+		}
+	});
+
+	BroadcastStream::new(rx)
+}
+
+async fn run_server() -> anyhow::Result<SocketAddr> {
+	let server = Server::builder().build("127.0.0.1:0").await?;
+	let mut module = RpcModule::new(());
+	module
+		.register_subscription("subscribe_hello", "s_hello", "unsubscribe_hello", |_, pending, _, _| async move {
+			let sub = pending.accept().await.unwrap();
+
+			for i in 0..usize::MAX {
+				let json = serde_json::value::to_raw_value(&i).unwrap();
+				sub.send(json).await.unwrap();
+				tokio::time::sleep(Duration::from_millis(10)).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)
+}