//! Contain structs related to making RPCs use std::sync::Arc; use std::time::Duration; use futures::future::join_all; use futures::stream::futures_unordered::FuturesUnordered; use futures::stream::StreamExt; use futures_util::future::FutureExt; use tokio::select; use tokio::sync::{watch, Semaphore}; pub use netapp::endpoint::{Endpoint, EndpointHandler, Message as Rpc}; use netapp::peering::fullmesh::FullMeshPeeringStrategy; pub use netapp::proto::*; pub use netapp::{NetApp, NodeID}; use garage_util::background::BackgroundRunner; use garage_util::data::*; use garage_util::error::Error; use crate::ring::Ring; const DEFAULT_TIMEOUT: Duration = Duration::from_secs(10); // Try to never have more than 200MB of outgoing requests // buffered at the same time. Other requests are queued until // space is freed. const REQUEST_BUFFER_SIZE: usize = 200 * 1024 * 1024; /// Strategy to apply when making RPC #[derive(Copy, Clone)] pub struct RequestStrategy { /// Max time to wait for reponse pub rs_timeout: Duration, /// Min number of response to consider the request successful pub rs_quorum: Option<usize>, /// Should requests be dropped after enough response are received pub rs_interrupt_after_quorum: bool, /// Request priority pub rs_priority: RequestPriority, } impl RequestStrategy { /// Create a RequestStrategy with default timeout and not interrupting when quorum reached pub fn with_priority(prio: RequestPriority) -> Self { RequestStrategy { rs_timeout: DEFAULT_TIMEOUT, rs_quorum: None, rs_interrupt_after_quorum: false, rs_priority: prio, } } /// Set quorum to be reached for request pub fn with_quorum(mut self, quorum: usize) -> Self { self.rs_quorum = Some(quorum); self } /// Set timeout of the strategy pub fn with_timeout(mut self, timeout: Duration) -> Self { self.rs_timeout = timeout; self } /// Set if requests can be dropped after quorum has been reached /// In general true for read requests, and false for write pub fn interrupt_after_quorum(mut self, interrupt: bool) -> Self { self.rs_interrupt_after_quorum = interrupt; self } } #[derive(Clone)] pub struct RpcHelper(Arc<RpcHelperInner>); struct RpcHelperInner { our_node_id: Uuid, fullmesh: Arc<FullMeshPeeringStrategy>, background: Arc<BackgroundRunner>, ring: watch::Receiver<Arc<Ring>>, request_buffer_semaphore: Semaphore, } impl RpcHelper { pub(crate) fn new( our_node_id: Uuid, fullmesh: Arc<FullMeshPeeringStrategy>, background: Arc<BackgroundRunner>, ring: watch::Receiver<Arc<Ring>>, ) -> Self { Self(Arc::new(RpcHelperInner { our_node_id, fullmesh, background, ring, request_buffer_semaphore: Semaphore::new(REQUEST_BUFFER_SIZE), })) } pub async fn call<M, H, S>( &self, endpoint: &Endpoint<M, H>, to: Uuid, msg: M, strat: RequestStrategy, ) -> Result<S, Error> where M: Rpc<Response = Result<S, Error>>, H: EndpointHandler<M>, { self.call_arc(endpoint, to, Arc::new(msg), strat).await } pub async fn call_arc<M, H, S>( &self, endpoint: &Endpoint<M, H>, to: Uuid, msg: Arc<M>, strat: RequestStrategy, ) -> Result<S, Error> where M: Rpc<Response = Result<S, Error>>, H: EndpointHandler<M>, { let msg_size = rmp_to_vec_all_named(&msg)?.len() as u32; let permit = self .0 .request_buffer_semaphore .acquire_many(msg_size) .await?; let node_id = to.into(); select! { res = endpoint.call(&node_id, &msg, strat.rs_priority) => { drop(permit); Ok(res??) } _ = tokio::time::sleep(strat.rs_timeout) => { drop(permit); Err(Error::Timeout) } } } pub async fn call_many<M, H, S>( &self, endpoint: &Endpoint<M, H>, to: &[Uuid], msg: M, strat: RequestStrategy, ) -> Vec<(Uuid, Result<S, Error>)> where M: Rpc<Response = Result<S, Error>>, H: EndpointHandler<M>, { let msg = Arc::new(msg); let resps = join_all( to.iter() .map(|to| self.call_arc(endpoint, *to, msg.clone(), strat)), ) .await; to.iter() .cloned() .zip(resps.into_iter()) .collect::<Vec<_>>() } pub async fn broadcast<M, H, S>( &self, endpoint: &Endpoint<M, H>, msg: M, strat: RequestStrategy, ) -> Vec<(Uuid, Result<S, Error>)> where M: Rpc<Response = Result<S, Error>>, H: EndpointHandler<M>, { let to = self .0 .fullmesh .get_peer_list() .iter() .map(|p| p.id.into()) .collect::<Vec<_>>(); self.call_many(endpoint, &to[..], msg, strat).await } /// Make a RPC call to multiple servers, returning either a Vec of responses, /// or an error if quorum could not be reached due to too many errors pub async fn try_call_many<M, H, S>( &self, endpoint: &Arc<Endpoint<M, H>>, to: &[Uuid], msg: M, strategy: RequestStrategy, ) -> Result<Vec<S>, Error> where M: Rpc<Response = Result<S, Error>> + 'static, H: EndpointHandler<M> + 'static, S: Send, { let msg = Arc::new(msg); // Build future for each request // They are not started now: they are added below in a FuturesUnordered // object that will take care of polling them (see below) let requests = to.iter().cloned().map(|to| { let self2 = self.clone(); let msg = msg.clone(); let endpoint2 = endpoint.clone(); (to, async move { self2.call_arc(&endpoint2, to, msg, strategy).await }) }); let quorum = strategy.rs_quorum.unwrap_or(to.len()); // Vectors in which success results and errors will be collected let mut successes = vec![]; let mut errors = vec![]; if strategy.rs_interrupt_after_quorum { // Case 1: once quorum is reached, other requests don't matter. // What we do here is only send the required number of requests // to reach a quorum, priorizing nodes with the lowest latency. // When there are errors, we start new requests to compensate. // Retrieve some status variables that we will use to sort requests let peer_list = self.0.fullmesh.get_peer_list(); let ring: Arc<Ring> = self.0.ring.borrow().clone(); let our_zone = match ring.config.members.get(&self.0.our_node_id) { Some(pc) => &pc.zone, None => "", }; // Augment requests with some information used to sort them. // The tuples are as follows: // (is another node?, is another zone?, latency, node ID, request future) // We store all of these tuples in a vec that we can sort. // By sorting this vec, we priorize ourself, then nodes in the same zone, // and within a same zone we priorize nodes with the lowest latency. let mut requests = requests .map(|(to, fut)| { let peer_zone = match ring.config.members.get(&to) { Some(pc) => &pc.zone, None => "", }; let peer_avg_ping = peer_list .iter() .find(|x| x.id.as_ref() == to.as_slice()) .map(|pi| pi.avg_ping) .flatten() .unwrap_or_else(|| Duration::from_secs(1)); ( to != self.0.our_node_id, peer_zone != our_zone, peer_avg_ping, to, fut, ) }) .collect::<Vec<_>>(); // Sort requests by (priorize ourself, priorize same zone, priorize low latency) requests .sort_by_key(|(diffnode, diffzone, ping, _to, _fut)| (*diffnode, *diffzone, *ping)); // Make an iterator to take requests in their sorted order let mut requests = requests.into_iter(); // resp_stream will contain all of the requests that are currently in flight. // (for the moment none, they will be added in the loop below) let mut resp_stream = FuturesUnordered::new(); // Do some requests and collect results 'request_loop: while successes.len() < quorum { // If the current set of requests that are running is not enough to possibly // reach quorum, start some new requests. while successes.len() + resp_stream.len() < quorum { if let Some((_, _, _, _to, fut)) = requests.next() { resp_stream.push(fut); } else { // If we have no request to add, we know that we won't ever // reach quorum: bail out now. break 'request_loop; } } assert!(!resp_stream.is_empty()); // because of loop invariants // Wait for one request to terminate match resp_stream.next().await.unwrap() { Ok(msg) => { successes.push(msg); } Err(e) => { errors.push(e); } } } } else { // Case 2: all of the requests need to be sent in all cases, // and need to terminate. (this is the case for writes that // must be spread to n nodes) // Just start all the requests in parallel and return as soon // as the quorum is reached. let mut resp_stream = requests .map(|(_, fut)| fut) .collect::<FuturesUnordered<_>>(); while let Some(resp) = resp_stream.next().await { match resp { Ok(msg) => { successes.push(msg); if successes.len() >= quorum { break; } } Err(e) => { errors.push(e); } } } if !resp_stream.is_empty() { // Continue remaining requests in background. // Continue the remaining requests immediately using tokio::spawn // but enqueue a task in the background runner // to ensure that the process won't exit until the requests are done // (if we had just enqueued the resp_stream.collect directly in the background runner, // the requests might have been put on hold in the background runner's queue, // in which case they might timeout or otherwise fail) let wait_finished_fut = tokio::spawn(async move { resp_stream.collect::<Vec<Result<_, _>>>().await; }); self.0.background.spawn(wait_finished_fut.map(|_| Ok(()))); } } if successes.len() >= quorum { Ok(successes) } else { let errors = errors.iter().map(|e| format!("{}", e)).collect::<Vec<_>>(); Err(Error::Quorum(quorum, successes.len(), to.len(), errors)) } } }