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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0
//! Implementation of the unary RPC protocol as per [DiemNet wire protocol v1].
//!
//! ## Design:
//!
//! The unary RPC protocol is implemented here as two independent async completion
//! queues: [`InboundRpcs`] and [`OutboundRpcs`].
//!
//! The `InboundRpcs` queue is responsible for handling inbound rpc requests
//! off-the-wire, forwarding the request to the application layer, waiting for
//! the application layer's response, and then enqueuing the rpc response to-be
//! written over-the-wire.
//!
//! Likewise, the `OutboundRpcs` queue is responsible for handling outbound rpc
//! requests from the application layer, enqueuing the request for writing onto
//! the wire, waiting for a corresponding rpc response, and then notifying the
//! requestor of the arrived response message.
//!
//! Both `InboundRpcs` and `OutboundRpcs` are owned and driven by the [`Peer`]
//! actor. This has a few implications. First, it means that each connection has
//! its own pair of local rpc completion queues; the queues are _not_ shared
//! across connections. Second, the queues don't do any IO work. They're purely
//! driven by the owning `Peer` actor, who calls `handle_` methods on new
//! [`NetworkMessage`] arrivals and polls for completed rpc requests. The queues
//! also do not write to the wire directly; instead, they're given a reference to
//! the [`Peer`] actor's write queue, which they can enqueue a new outbound
//! [`NetworkMessage`] onto.
//!
//! ## Timeouts:
//!
//! Both inbound and outbound requests have mandatory timeouts. The tasks in the
//! async completion queues are each wrapped in a `timeout` future, which causes
//! the task to complete with an error if the task isn't fulfilled before the
//! deadline.
//!
//! ## Limits:
//!
//! We limit the number of pending inbound and outbound RPC tasks to ensure that
//! resource usage is bounded.
//!
//! [DiemNet wire protocol v1]: https://github.com/diem/diem/blob/main/specifications/network/messaging-v1.md
//! [`Peer`]: crate::peer::Peer
use crate::{
counters::{
self, CANCELED_LABEL, DECLINED_LABEL, FAILED_LABEL, RECEIVED_LABEL, REQUEST_LABEL,
RESPONSE_LABEL, SENT_LABEL,
},
logging::NetworkSchema,
peer::PeerNotification,
peer_manager::PeerManagerError,
protocols::wire::messaging::v1::{
NetworkMessage, Priority, RequestId, RpcRequest, RpcResponse,
},
ProtocolId,
};
use anyhow::anyhow;
use bytes::Bytes;
use channel::diem_channel;
use diem_config::network_id::NetworkContext;
use diem_logger::prelude::*;
use diem_time_service::{timeout, TimeService, TimeServiceTrait};
use diem_types::PeerId;
use error::RpcError;
use futures::{
channel::oneshot,
future::{BoxFuture, FusedFuture, Future, FutureExt},
sink::SinkExt,
stream::{FuturesUnordered, StreamExt},
};
use serde::Serialize;
use short_hex_str::AsShortHexStr;
use std::{cmp::PartialEq, collections::HashMap, fmt::Debug, sync::Arc, time::Duration};
pub mod error;
/// A wrapper struct for an inbound rpc request and its associated context.
#[derive(Debug)]
pub struct InboundRpcRequest {
/// The [`ProtocolId`] for which of our upstream application modules should
/// handle (i.e., deserialize and then respond to) this inbound rpc request.
///
/// For example, if `protocol_id == ProtocolId::ConsensusRpc`, then this
/// inbound rpc request will be dispatched to consensus for handling.
pub protocol_id: ProtocolId,
/// The serialized request data received from the sender. At this layer in
/// the stack, the request data is just an opaque blob and will only be fully
/// deserialized later in the handling application module.
pub data: Bytes,
/// Channel over which the rpc response is sent from the upper application
/// layer to the network rpc layer.
///
/// The rpc actor holds onto the receiving end of this channel, awaiting the
/// response from the upper layer. If there is an error in, e.g.,
/// deserializing the request, the upper layer should send an [`RpcError`]
/// down the channel to signify that there was an error while handling this
/// rpc request. Currently, we just log these errors and drop the request.
///
/// The upper client layer should be prepared for `res_tx` to be disconnected
/// when trying to send their response, as the rpc call might have timed out
/// while handling the request.
pub res_tx: oneshot::Sender<Result<Bytes, RpcError>>,
}
/// A wrapper struct for an outbound rpc request and its associated context.
#[derive(Debug, Serialize)]
pub struct OutboundRpcRequest {
/// The remote peer's application module that should handle our outbound rpc
/// request.
///
/// For example, if `protocol_id == ProtocolId::ConsensusRpc`, then this
/// outbound rpc request should be handled by the remote peer's consensus
/// application module.
pub protocol_id: ProtocolId,
/// The serialized request data to be sent to the receiver. At this layer in
/// the stack, the request data is just an opaque blob.
#[serde(skip)]
pub data: Bytes,
/// Channel over which the rpc response is sent from the rpc layer to the
/// upper client layer.
///
/// If there is an error while performing the rpc protocol, e.g., the remote
/// peer drops the connection, we will send an [`RpcError`] over the channel.
#[serde(skip)]
pub res_tx: oneshot::Sender<Result<Bytes, RpcError>>,
/// The timeout duration for the entire rpc call. If the timeout elapses, the
/// rpc layer will send an [`RpcError::TimedOut`] error over the
/// `res_tx` channel to the upper client layer.
pub timeout: Duration,
}
// Wraps the task of request id generation. Request ids start at 0 and increment till they hit
// RequestId::MAX. After that, they wrap around to 0.
struct RequestIdGenerator {
next_id: RequestId,
}
impl RequestIdGenerator {
pub fn new() -> Self {
Self { next_id: 0 }
}
pub fn next(&mut self) -> RequestId {
let request_id = self.next_id;
self.next_id = self.next_id.wrapping_add(1);
request_id
}
}
impl PartialEq for InboundRpcRequest {
fn eq(&self, other: &Self) -> bool {
self.protocol_id == other.protocol_id && self.data == other.data
}
}
/// `InboundRpcs` handles new inbound rpc requests off the wire, notifies the
/// `PeerManager` of the new request, and stores the pending response on a queue.
/// If the response eventually completes, `InboundRpc` records some metrics and
/// enqueues the response message onto the outbound write queue.
///
/// There is one `InboundRpcs` handler per [`Peer`](crate::peer::Peer).
pub struct InboundRpcs {
/// The network instance this Peer actor is running under.
network_context: Arc<NetworkContext>,
/// A handle to a time service for easily mocking time-related operations.
time_service: TimeService,
/// The PeerId of this connection's remote peer. Used for logging.
remote_peer_id: PeerId,
/// The core async queue of pending inbound rpc tasks. The tasks are driven
/// to completion by the `InboundRpcs::next_completed_response()` method.
inbound_rpc_tasks: FuturesUnordered<BoxFuture<'static, Result<RpcResponse, RpcError>>>,
/// A blanket timeout on all inbound rpc requests. If the application handler
/// doesn't respond to the request before this timeout, the request will be
/// dropped.
inbound_rpc_timeout: Duration,
/// Only allow this many concurrent inbound rpcs at one time from this remote
/// peer. New inbound requests exceeding this limit will be dropped.
max_concurrent_inbound_rpcs: u32,
}
impl InboundRpcs {
pub fn new(
network_context: Arc<NetworkContext>,
time_service: TimeService,
remote_peer_id: PeerId,
inbound_rpc_timeout: Duration,
max_concurrent_inbound_rpcs: u32,
) -> Self {
Self {
network_context,
time_service,
remote_peer_id,
inbound_rpc_tasks: FuturesUnordered::new(),
inbound_rpc_timeout,
max_concurrent_inbound_rpcs,
}
}
/// Handle a new inbound `RpcRequest` message off the wire.
pub fn handle_inbound_request(
&mut self,
peer_notifs_tx: &mut diem_channel::Sender<ProtocolId, PeerNotification>,
request: RpcRequest,
) -> Result<(), RpcError> {
let network_context = &self.network_context;
// Drop new inbound requests if our completion queue is at capacity.
if self.inbound_rpc_tasks.len() as u32 == self.max_concurrent_inbound_rpcs {
// Increase counter of declined responses and log warning.
counters::rpc_messages(network_context, RESPONSE_LABEL, DECLINED_LABEL).inc();
return Err(RpcError::TooManyPending(self.max_concurrent_inbound_rpcs));
}
let protocol_id = request.protocol_id;
let request_id = request.request_id;
let priority = request.priority;
let req_len = request.raw_request.len() as u64;
trace!(
NetworkSchema::new(network_context).remote_peer(&self.remote_peer_id),
"{} Received inbound rpc request from peer {} with request_id {} and protocol_id {}",
network_context,
self.remote_peer_id.short_str(),
request_id,
protocol_id,
);
// Collect counters for received request.
counters::rpc_messages(network_context, REQUEST_LABEL, RECEIVED_LABEL).inc();
counters::rpc_bytes(network_context, REQUEST_LABEL, RECEIVED_LABEL).inc_by(req_len);
let timer =
counters::inbound_rpc_handler_latency(network_context, protocol_id).start_timer();
// Foward request to PeerManager for handling.
let (response_tx, response_rx) = oneshot::channel();
let notif = PeerNotification::RecvRpc(InboundRpcRequest {
protocol_id,
data: Bytes::from(request.raw_request),
res_tx: response_tx,
});
if let Err(err) = peer_notifs_tx.push(protocol_id, notif) {
counters::rpc_messages(network_context, RESPONSE_LABEL, FAILED_LABEL).inc();
return Err(err.into());
}
// Create a new task that waits for a response from the upper layer with a timeout.
let inbound_rpc_task = self
.time_service
.timeout(self.inbound_rpc_timeout, response_rx)
.map(move |result| {
// Flatten the errors
let maybe_response = match result {
Ok(Ok(Ok(response_bytes))) => Ok(RpcResponse {
request_id,
priority,
raw_response: Vec::from(response_bytes.as_ref()),
}),
Ok(Ok(Err(err))) => Err(err),
Ok(Err(oneshot::Canceled)) => Err(RpcError::UnexpectedResponseChannelCancel),
Err(timeout::Elapsed) => Err(RpcError::TimedOut),
};
// Only record latency of successful requests
match maybe_response {
Ok(_) => timer.stop_and_record(),
Err(_) => timer.stop_and_discard(),
};
maybe_response
})
.boxed();
// Add that task to the inbound completion queue. These tasks are driven
// forward by `Peer` awaiting `self.next_completed_response()`.
self.inbound_rpc_tasks.push(inbound_rpc_task);
Ok(())
}
/// Method for `Peer` actor to drive the pending inbound rpc tasks forward.
/// The returned `Future` is a `FusedFuture` so it works correctly in a
/// `futures::select!`.
pub fn next_completed_response(
&mut self,
) -> impl Future<Output = Result<RpcResponse, RpcError>> + FusedFuture + '_ {
self.inbound_rpc_tasks.select_next_some()
}
/// Handle a completed response from the application handler. If successful,
/// we update the appropriate counters and enqueue the response message onto
/// the outbound write queue.
pub async fn send_outbound_response(
&mut self,
write_reqs_tx: &mut channel::Sender<(
NetworkMessage,
oneshot::Sender<Result<(), PeerManagerError>>,
)>,
maybe_response: Result<RpcResponse, RpcError>,
) -> Result<(), RpcError> {
let network_context = &self.network_context;
let response = match maybe_response {
Ok(response) => response,
Err(err) => {
counters::rpc_messages(network_context, RESPONSE_LABEL, FAILED_LABEL).inc();
return Err(err);
}
};
let res_len = response.raw_response.len() as u64;
// Send outbound response to remote peer.
trace!(
NetworkSchema::new(network_context).remote_peer(&self.remote_peer_id),
"{} Sending rpc response to peer {} for request_id {}",
network_context,
self.remote_peer_id.short_str(),
response.request_id,
);
let message = NetworkMessage::RpcResponse(response);
let (ack_tx, _) = oneshot::channel();
write_reqs_tx.send((message, ack_tx)).await?;
// Collect counters for sent response.
counters::rpc_messages(network_context, RESPONSE_LABEL, SENT_LABEL).inc();
counters::rpc_bytes(network_context, RESPONSE_LABEL, SENT_LABEL).inc_by(res_len);
Ok(())
}
}
/// `OutboundRpcs` handles new outbound rpc requests made from the application layer.
///
/// There is one `OutboundRpcs` handler per [`Peer`](crate::peer::Peer).
pub struct OutboundRpcs {
/// The network instance this Peer actor is running under.
network_context: Arc<NetworkContext>,
/// A handle to a time service for easily mocking time-related operations.
time_service: TimeService,
/// The PeerId of this connection's remote peer. Used for logging.
remote_peer_id: PeerId,
/// Generates the next RequestId to use for the next outbound RPC. Note that
/// request ids are local to each connection.
request_id_gen: RequestIdGenerator,
/// A completion queue of pending outbound rpc tasks. Each task waits for
/// either a successful `RpcResponse` message, handed to it via the channel
/// in `pending_outbound_rpcs`, or waits for a timeout or cancellation
/// notification. After completion, the task will yield its `RequestId` and
/// other metadata (success/failure, success latency, response length) via
/// the future from `next_completed_request`.
outbound_rpc_tasks:
FuturesUnordered<BoxFuture<'static, (RequestId, Result<(f64, u64), RpcError>)>>,
/// Maps a `RequestId` into a handle to a task in the `outbound_rpc_tasks`
/// completion queue. When a new `RpcResponse` message comes in, we will use
/// this map to notify the corresponding task that its response has arrived.
pending_outbound_rpcs: HashMap<RequestId, oneshot::Sender<RpcResponse>>,
/// Only allow this many concurrent outbound rpcs at one time from this remote
/// peer. New outbound requests exceeding this limit will be dropped.
max_concurrent_outbound_rpcs: u32,
}
impl OutboundRpcs {
pub fn new(
network_context: Arc<NetworkContext>,
time_service: TimeService,
remote_peer_id: PeerId,
max_concurrent_outbound_rpcs: u32,
) -> Self {
Self {
network_context,
time_service,
remote_peer_id,
request_id_gen: RequestIdGenerator::new(),
outbound_rpc_tasks: FuturesUnordered::new(),
pending_outbound_rpcs: HashMap::new(),
max_concurrent_outbound_rpcs,
}
}
/// Handle a new outbound rpc request from the application layer.
pub async fn handle_outbound_request(
&mut self,
request: OutboundRpcRequest,
write_reqs_tx: &mut channel::Sender<(
NetworkMessage,
oneshot::Sender<Result<(), PeerManagerError>>,
)>,
) -> Result<(), RpcError> {
let network_context = &self.network_context;
let peer_id = &self.remote_peer_id;
// Unpack request.
let OutboundRpcRequest {
protocol_id,
data: request_data,
timeout,
res_tx: mut application_response_tx,
} = request;
let req_len = request_data.len() as u64;
// Drop the outbound request if the application layer has already canceled.
if application_response_tx.is_canceled() {
counters::rpc_messages(network_context, REQUEST_LABEL, CANCELED_LABEL).inc();
return Err(RpcError::UnexpectedResponseChannelCancel);
}
// Drop new outbound requests if our completion queue is at capacity.
if self.outbound_rpc_tasks.len() == self.max_concurrent_outbound_rpcs as usize {
counters::rpc_messages(network_context, REQUEST_LABEL, DECLINED_LABEL).inc();
// Notify application that their request was dropped due to capacity.
let err = Err(RpcError::TooManyPending(self.max_concurrent_outbound_rpcs));
let _ = application_response_tx.send(err);
return Err(RpcError::TooManyPending(self.max_concurrent_outbound_rpcs));
}
let request_id = self.request_id_gen.next();
trace!(
NetworkSchema::new(network_context).remote_peer(peer_id),
"{} Sending outbound rpc request with request_id {} and protocol_id {} to {}",
network_context,
request_id,
protocol_id,
peer_id.short_str(),
);
// Start timer to collect outbound RPC latency.
let timer =
counters::outbound_rpc_request_latency(network_context, protocol_id).start_timer();
// Enqueue rpc request message onto outbound write queue.
let message = NetworkMessage::RpcRequest(RpcRequest {
protocol_id,
request_id,
priority: Priority::default(),
raw_request: Vec::from(request_data.as_ref()),
});
let (ack_tx, _) = oneshot::channel();
write_reqs_tx.send((message, ack_tx)).await?;
// Collect counters for requests sent.
counters::rpc_messages(network_context, REQUEST_LABEL, SENT_LABEL).inc();
counters::rpc_bytes(network_context, REQUEST_LABEL, SENT_LABEL).inc_by(req_len);
// Create channel over which response is delivered to outbound_rpc_task.
let (response_tx, response_rx) = oneshot::channel::<RpcResponse>();
// Store send-side in the pending map so we can notify outbound_rpc_task
// when the rpc response has arrived.
self.pending_outbound_rpcs.insert(request_id, response_tx);
// A future that waits for the rpc response with a timeout. We create the
// timeout out here to start the timer as soon as we push onto the queue
// (as opposed to whenever it first gets polled on the queue).
let wait_for_response = self
.time_service
.timeout(timeout, response_rx)
.map(|result| {
// Flatten errors.
match result {
Ok(Ok(response)) => Ok(Bytes::from(response.raw_response)),
Ok(Err(oneshot::Canceled)) => Err(RpcError::UnexpectedResponseChannelCancel),
Err(timeout::Elapsed) => Err(RpcError::TimedOut),
}
});
// A future that waits for the response and sends it to the application.
let notify_application = async move {
// This future will complete if the application layer cancels the request.
let mut cancellation = application_response_tx.cancellation().fuse();
// Pin the response future to the stack so we don't have to box it.
tokio::pin!(wait_for_response);
futures::select! {
maybe_response = wait_for_response => {
// TODO(philiphayes): Clean up RpcError. Effectively need to
// clone here to pass the result up to application layer, but
// RpcError is not currently cloneable.
let result_copy = match &maybe_response {
Ok(response) => Ok(response.len() as u64),
Err(err) => Err(RpcError::Error(anyhow!(err.to_string()))),
};
// Notify the application of the results.
application_response_tx.send(maybe_response).map_err(|_| RpcError::UnexpectedResponseChannelCancel)?;
result_copy
}
_ = cancellation => Err(RpcError::UnexpectedResponseChannelCancel),
}
};
let outbound_rpc_task = async move {
// Always return the request_id so we can garbage collect the
// pending_outbound_rpcs map.
match notify_application.await {
Ok(response_len) => {
let latency = timer.stop_and_record();
(request_id, Ok((latency, response_len)))
}
Err(err) => {
// don't record
timer.stop_and_discard();
(request_id, Err(err))
}
}
};
self.outbound_rpc_tasks.push(outbound_rpc_task.boxed());
Ok(())
}
/// Method for `Peer` actor to drive the pending outbound rpc tasks forward.
/// The returned `Future` is a `FusedFuture` so it works correctly in a
/// `futures::select!`.
pub fn next_completed_request(
&mut self,
) -> impl Future<Output = (RequestId, Result<(f64, u64), RpcError>)> + FusedFuture + '_ {
self.outbound_rpc_tasks.select_next_some()
}
/// Handle a newly completed task from the `self.outbound_rpc_tasks` queue.
/// At this point, the application layer's request has already been fulfilled;
/// we just need to clean up this request and update some counters.
pub fn handle_completed_request(
&mut self,
request_id: RequestId,
result: Result<(f64, u64), RpcError>,
) {
// Remove request_id from pending_outbound_rpcs if not already removed.
//
// We don't care about the value from `remove` here. If the request
// timed-out or was canceled, it will still be in the pending map.
// Otherwise, if we received a response for our request, we will have
// removed and triggered the oneshot from the pending map, notifying us.
let _ = self.pending_outbound_rpcs.remove(&request_id);
let network_context = &self.network_context;
let peer_id = &self.remote_peer_id;
match result {
Ok((latency, request_len)) => {
counters::rpc_messages(network_context, RESPONSE_LABEL, RECEIVED_LABEL).inc();
counters::rpc_bytes(network_context, RESPONSE_LABEL, RECEIVED_LABEL)
.inc_by(request_len);
trace!(
NetworkSchema::new(network_context).remote_peer(peer_id),
"{} Received response for request_id {} from peer {} \
with {:.6} seconds of latency",
network_context,
request_id,
peer_id.short_str(),
latency,
);
}
Err(err) => {
if let RpcError::UnexpectedResponseChannelCancel = err {
counters::rpc_messages(network_context, REQUEST_LABEL, CANCELED_LABEL).inc();
} else {
counters::rpc_messages(network_context, REQUEST_LABEL, FAILED_LABEL).inc();
}
warn!(
NetworkSchema::new(network_context).remote_peer(peer_id),
"{} Error making outbound rpc request with request_id {} to {}: {}",
network_context,
request_id,
peer_id.short_str(),
err
);
}
}
}
/// Handle a new inbound `RpcResponse` message. If we have a pending request
/// with a matching request id in the `pending_outbound_rpcs` map, this will
/// trigger that corresponding task to wake up and complete in
/// `handle_completed_request`.
pub fn handle_inbound_response(&mut self, response: RpcResponse) {
let network_context = &self.network_context;
let peer_id = &self.remote_peer_id;
let request_id = response.request_id;
let is_canceled = if let Some(response_tx) = self.pending_outbound_rpcs.remove(&request_id)
{
response_tx.send(response).is_err()
} else {
true
};
if is_canceled {
info!(
NetworkSchema::new(network_context).remote_peer(peer_id),
request_id = request_id,
"{} Received response for expired request_id {} from {}. Discarding.",
network_context,
request_id,
peer_id.short_str(),
);
} else {
trace!(
NetworkSchema::new(network_context).remote_peer(peer_id),
request_id = request_id,
"{} Notified pending outbound rpc task of inbound response for request_id {} from {}",
network_context,
request_id,
peer_id.short_str(),
);
}
}
}