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/cli/src/commands/run_cmd.rs

@@ -25,7 +25,7 @@ use crate::{
 	},
 	CliConfiguration, PrometheusParams, RuntimeParams, TelemetryParams,
 	RPC_DEFAULT_MAX_CONNECTIONS, RPC_DEFAULT_MAX_REQUEST_SIZE_MB, RPC_DEFAULT_MAX_RESPONSE_SIZE_MB,
-	RPC_DEFAULT_MAX_SUBS_PER_CONN,
+	RPC_DEFAULT_MAX_SUBS_PER_CONN, RPC_DEFAULT_MESSAGE_CAPACITY_PER_CONN,
 };
 use clap::Parser;
 use regex::Regex;
@@ -102,9 +102,20 @@ pub struct RunCmd {
 	#[arg(long, value_name = "COUNT", default_value_t = RPC_DEFAULT_MAX_CONNECTIONS)]
 	pub rpc_max_connections: u32,
 
-	/// Specify browser *origins* allowed to access the HTTP and WS RPC servers.
+	/// The number of messages the RPC server is allowed to keep in memory.
 	///
-	/// A comma-separated list of origins (`protocol://domain` or special `null`
+	/// If the buffer becomes full then the server will not process
+	/// new messages until the connected client start reading the
+	/// underlying messages.
+	///
+	/// This applies per connection which includes both
+	/// JSON-RPC methods calls and subscriptions.
+	#[arg(long, default_value_t = RPC_DEFAULT_MESSAGE_CAPACITY_PER_CONN)]
+	pub rpc_message_buffer_capacity_per_connection: u32,
+
+	/// Specify browser *origins* allowed to access the HTTP & WS RPC servers.
+	///
+	/// A comma-separated list of origins (protocol://domain or special `null`
 	/// value). Value of `all` will disable origin validation. Default is to
 	/// allow localhost and <https://polkadot.js.org> origins. When running in
 	/// `--dev` mode the default is to allow all origins.

substrate/client/cli/src/config.rs

@@ -52,8 +52,11 @@ pub const RPC_DEFAULT_MAX_SUBS_PER_CONN: u32 = 1024;
 pub const RPC_DEFAULT_MAX_REQUEST_SIZE_MB: u32 = 15;
 /// The default max response size in MB.
 pub const RPC_DEFAULT_MAX_RESPONSE_SIZE_MB: u32 = 15;
-/// The default number of connection..
+/// The default concurrent connection limit.
 pub const RPC_DEFAULT_MAX_CONNECTIONS: u32 = 100;
+/// The default number of messages the RPC server
+/// is allowed to keep in memory per connection.
+pub const RPC_DEFAULT_MESSAGE_CAPACITY_PER_CONN: u32 = 64;
 
 /// Default configuration values used by Substrate
 ///
@@ -330,6 +333,11 @@ pub trait CliConfiguration<DCV: DefaultConfigurationValues = ()>: Sized {
 		Ok(RPC_DEFAULT_MAX_SUBS_PER_CONN)
 	}
 
+	/// The number of messages the RPC server is allowed to keep in memory per connection.
+	fn rpc_buffer_capacity_per_connection(&self) -> Result<u32> {
+		Ok(RPC_DEFAULT_MESSAGE_CAPACITY_PER_CONN)
+	}
+
 	/// Get the prometheus configuration (`None` if disabled)
 	///
 	/// By default this is `None`.
@@ -501,6 +509,7 @@ pub trait CliConfiguration<DCV: DefaultConfigurationValues = ()>: Sized {
 			rpc_id_provider: None,
 			rpc_max_subs_per_conn: self.rpc_max_subscriptions_per_connection()?,
 			rpc_port: DCV::rpc_listen_port(),
+			rpc_message_buffer_capacity: self.rpc_buffer_capacity_per_connection()?,
 			prometheus_config: self
 				.prometheus_config(DCV::prometheus_listen_port(), &chain_spec)?,
 			telemetry_endpoints,

substrate/client/cli/src/runner.rs

@@ -269,6 +269,7 @@ mod tests {
 				rpc_max_response_size: Default::default(),
 				rpc_id_provider: Default::default(),
 				rpc_max_subs_per_conn: Default::default(),
+				rpc_message_buffer_capacity: Default::default(),
 				rpc_port: 9944,
 				prometheus_config: None,
 				telemetry_endpoints: None,