rpc: backpressured RPC server (bump jsonrpsee 0.20) (#1313)

This is a rather big change in jsonrpsee, the major things in this bump
are:
- Server backpressure (the subscription impls are modified to deal with
that)
- Allow custom error types / return types (remove jsonrpsee::core::Error
and jsonrpee::core::CallError)
- Bug fixes (graceful shutdown in particular not used by substrate
anyway)
   - Less dependencies for the clients in particular
   - Return type requires Clone in method call responses
   - Moved to tokio channels
   - Async subscription API (not used in this PR)

Major changes in this PR:
- The subscriptions are now bounded and if subscription can't keep up
with the server it is dropped
- CLI: add parameter to configure the jsonrpc server bounded message
buffer (default is 64)
- Add our own subscription helper to deal with the unbounded streams in
substrate

The most important things in this PR to review is the added helpers
functions in `substrate/client/rpc/src/utils.rs` and the rest is pretty
much chore.

Regarding the "bounded buffer limit" it may cause the server to handle
the JSON-RPC calls
slower than before.

The message size limit is bounded by "--rpc-response-size" thus "by
default 10MB * 64 = 640MB"
but the subscription message size is not covered by this limit and could
be capped as well.

Hopefully the last release prior to 1.0, sorry in advance for a big PR

Previous attempt: https://github.com/paritytech/substrate/pull/13992

Resolves https://github.com/paritytech/polkadot-sdk/issues/748, resolves
https://github.com/paritytech/polkadot-sdk/issues/627

substrate/client/rpc/src/chain/chain_full.rs

@@ -19,14 +19,17 @@
 //! Blockchain API backend for full nodes.
 
 use super::{client_err, ChainBackend, Error};
-use crate::SubscriptionTaskExecutor;
+use crate::{
+	utils::{pipe_from_stream, spawn_subscription_task},
+	SubscriptionTaskExecutor,
+};
 use std::{marker::PhantomData, sync::Arc};
 
 use futures::{
-	future::{self, FutureExt},
+	future::{self},
 	stream::{self, Stream, StreamExt},
 };
-use jsonrpsee::SubscriptionSink;
+use jsonrpsee::{core::async_trait, PendingSubscriptionSink};
 use sc_client_api::{BlockBackend, BlockchainEvents};
 use sp_blockchain::HeaderBackend;
 use sp_runtime::{generic::SignedBlock, traits::Block as BlockT};
@@ -48,6 +51,7 @@ impl<Block: BlockT, Client> FullChain<Block, Client> {
 	}
 }
 
+#[async_trait]
 impl<Block, Client> ChainBackend<Client, Block> for FullChain<Block, Client>
 where
 	Block: BlockT + 'static,
@@ -66,11 +70,11 @@ where
 		self.client.block(self.unwrap_or_best(hash)).map_err(client_err)
 	}
 
-	fn subscribe_all_heads(&self, sink: SubscriptionSink) {
+	fn subscribe_all_heads(&self, pending: PendingSubscriptionSink) {
 		subscribe_headers(
 			&self.client,
 			&self.executor,
-			sink,
+			pending,
 			|| self.client().info().best_hash,
 			|| {
 				self.client()
@@ -80,11 +84,11 @@ where
 		)
 	}
 
-	fn subscribe_new_heads(&self, sink: SubscriptionSink) {
+	fn subscribe_new_heads(&self, pending: PendingSubscriptionSink) {
 		subscribe_headers(
 			&self.client,
 			&self.executor,
-			sink,
+			pending,
 			|| self.client().info().best_hash,
 			|| {
 				self.client()
@@ -95,11 +99,11 @@ where
 		)
 	}
 
-	fn subscribe_finalized_heads(&self, sink: SubscriptionSink) {
+	fn subscribe_finalized_heads(&self, pending: PendingSubscriptionSink) {
 		subscribe_headers(
 			&self.client,
 			&self.executor,
-			sink,
+			pending,
 			|| self.client().info().finalized_hash,
 			|| {
 				self.client()
@@ -114,7 +118,7 @@ where
 fn subscribe_headers<Block, Client, F, G, S>(
 	client: &Arc<Client>,
 	executor: &SubscriptionTaskExecutor,
-	mut sink: SubscriptionSink,
+	pending: PendingSubscriptionSink,
 	best_block_hash: G,
 	stream: F,
 ) where
@@ -139,9 +143,5 @@ fn subscribe_headers<Block, Client, F, G, S>(
 	// duplicates at the beginning of the stream though.
 	let stream = stream::iter(maybe_header).chain(stream());
 
-	let fut = async move {
-		sink.pipe_from_stream(stream).await;
-	};
-
-	executor.spawn("substrate-rpc-subscription", Some("rpc"), fut.boxed());
+	spawn_subscription_task(executor, pipe_from_stream(pending, stream));
 }

substrate/client/rpc/src/chain/mod.rs

@@ -27,7 +27,7 @@ use std::sync::Arc;
 
 use crate::SubscriptionTaskExecutor;
 
-use jsonrpsee::{core::RpcResult, types::SubscriptionResult, SubscriptionSink};
+use jsonrpsee::{core::async_trait, PendingSubscriptionSink};
 use sc_client_api::BlockchainEvents;
 use sp_rpc::{list::ListOrValue, number::NumberOrHex};
 use sp_runtime::{
@@ -42,6 +42,7 @@ pub use sc_rpc_api::chain::*;
 use sp_blockchain::HeaderBackend;
 
 /// Blockchain backend API
+#[async_trait]
 trait ChainBackend<Client, Block: BlockT>: Send + Sync + 'static
 where
 	Block: BlockT + 'static,
@@ -91,13 +92,13 @@ where
 	}
 
 	/// All new head subscription
-	fn subscribe_all_heads(&self, sink: SubscriptionSink);
+	fn subscribe_all_heads(&self, pending: PendingSubscriptionSink);
 
 	/// New best head subscription
-	fn subscribe_new_heads(&self, sink: SubscriptionSink);
+	fn subscribe_new_heads(&self, pending: PendingSubscriptionSink);
 
 	/// Finalized head subscription
-	fn subscribe_finalized_heads(&self, sink: SubscriptionSink);
+	fn subscribe_finalized_heads(&self, pending: PendingSubscriptionSink);
 }
 
 /// Create new state API that works on full node.
@@ -118,6 +119,7 @@ pub struct Chain<Block: BlockT, Client> {
 	backend: Box<dyn ChainBackend<Client, Block>>,
 }
 
+#[async_trait]
 impl<Block, Client> ChainApiServer<NumberFor<Block>, Block::Hash, Block::Header, SignedBlock<Block>>
 	for Chain<Block, Client>
 where
@@ -125,20 +127,20 @@ where
 	Block::Header: Unpin,
 	Client: HeaderBackend<Block> + BlockchainEvents<Block> + 'static,
 {
-	fn header(&self, hash: Option<Block::Hash>) -> RpcResult<Option<Block::Header>> {
-		self.backend.header(hash).map_err(Into::into)
+	fn header(&self, hash: Option<Block::Hash>) -> Result<Option<Block::Header>, Error> {
+		self.backend.header(hash)
 	}
 
-	fn block(&self, hash: Option<Block::Hash>) -> RpcResult<Option<SignedBlock<Block>>> {
-		self.backend.block(hash).map_err(Into::into)
+	fn block(&self, hash: Option<Block::Hash>) -> Result<Option<SignedBlock<Block>>, Error> {
+		self.backend.block(hash)
 	}
 
 	fn block_hash(
 		&self,
 		number: Option<ListOrValue<NumberOrHex>>,
-	) -> RpcResult<ListOrValue<Option<Block::Hash>>> {
+	) -> Result<ListOrValue<Option<Block::Hash>>, Error> {
 		match number {
-			None => self.backend.block_hash(None).map(ListOrValue::Value).map_err(Into::into),
+			None => self.backend.block_hash(None).map(ListOrValue::Value),
 			Some(ListOrValue::Value(number)) => self
 				.backend
 				.block_hash(Some(number))
@@ -152,23 +154,20 @@ where
 		}
 	}
 
-	fn finalized_head(&self) -> RpcResult<Block::Hash> {
-		self.backend.finalized_head().map_err(Into::into)
+	fn finalized_head(&self) -> Result<Block::Hash, Error> {
+		self.backend.finalized_head()
 	}
 
-	fn subscribe_all_heads(&self, sink: SubscriptionSink) -> SubscriptionResult {
-		self.backend.subscribe_all_heads(sink);
-		Ok(())
+	fn subscribe_all_heads(&self, pending: PendingSubscriptionSink) {
+		self.backend.subscribe_all_heads(pending);
 	}
 
-	fn subscribe_new_heads(&self, sink: SubscriptionSink) -> SubscriptionResult {
-		self.backend.subscribe_new_heads(sink);
-		Ok(())
+	fn subscribe_new_heads(&self, pending: PendingSubscriptionSink) {
+		self.backend.subscribe_new_heads(pending)
 	}
 
-	fn subscribe_finalized_heads(&self, sink: SubscriptionSink) -> SubscriptionResult {
-		self.backend.subscribe_finalized_heads(sink);
-		Ok(())
+	fn subscribe_finalized_heads(&self, pending: PendingSubscriptionSink) {
+		self.backend.subscribe_finalized_heads(pending)
 	}
 }
 

substrate/client/rpc/src/chain/tests.rs

@@ -19,7 +19,7 @@
 use super::*;
 use crate::testing::{test_executor, timeout_secs};
 use assert_matches::assert_matches;
-use jsonrpsee::types::EmptyServerParams as EmptyParams;
+use jsonrpsee::core::EmptyServerParams as EmptyParams;
 use sc_block_builder::BlockBuilderBuilder;
 use sp_consensus::BlockOrigin;
 use sp_rpc::list::ListOrValue;
@@ -252,7 +252,7 @@ async fn test_head_subscription(method: &str) {
 
 	let mut sub = {
 		let api = new_full(client.clone(), test_executor()).into_rpc();
-		let sub = api.subscribe(method, EmptyParams::new()).await.unwrap();
+		let sub = api.subscribe_unbounded(method, EmptyParams::new()).await.unwrap();
 		let block = BlockBuilderBuilder::new(&*client)
 			.on_parent_block(client.chain_info().best_hash)
 			.with_parent_block_number(client.chain_info().best_number)