garage/src/rpc/rpc_helper.rs

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//! 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};
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pub use netapp::endpoint::{Endpoint, EndpointHandler, Message as Rpc};
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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;
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use crate::ring::Ring;
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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;
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/// 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,
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}
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>(
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&self,
endpoint: &Endpoint<M, H>,
to: Uuid,
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msg: M,
strat: RequestStrategy,
) -> Result<S, Error>
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where
M: Rpc<Response = Result<S, Error>>,
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H: EndpointHandler<M>,
{
self.call_arc(endpoint, to, Arc::new(msg), strat).await
}
pub async fn call_arc<M, H, S>(
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&self,
endpoint: &Endpoint<M, H>,
to: Uuid,
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msg: Arc<M>,
strat: RequestStrategy,
) -> Result<S, Error>
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where
M: Rpc<Response = Result<S, Error>>,
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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();
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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)
}
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}
}
pub async fn call_many<M, H, S>(
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&self,
endpoint: &Endpoint<M, H>,
to: &[Uuid],
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msg: M,
strat: RequestStrategy,
) -> Vec<(Uuid, Result<S, Error>)>
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where
M: Rpc<Response = Result<S, Error>>,
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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>(
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&self,
endpoint: &Endpoint<M, H>,
msg: M,
strat: RequestStrategy,
) -> Vec<(Uuid, Result<S, Error>)>
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where
M: Rpc<Response = Result<S, Error>>,
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H: EndpointHandler<M>,
{
let to = self
.0
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.fullmesh
.get_peer_list()
.iter()
.map(|p| p.id.into())
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.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>(
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&self,
endpoint: &Arc<Endpoint<M, H>>,
to: &[Uuid],
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msg: M,
strategy: RequestStrategy,
) -> Result<Vec<S>, Error>
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where
M: Rpc<Response = Result<S, Error>> + 'static,
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H: EndpointHandler<M> + 'static,
S: Send,
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{
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
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})
});
let quorum = strategy.rs_quorum.unwrap_or(to.len());
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// Vectors in which success results and errors will be collected
let mut successes = vec![];
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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;
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}
}
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);
}
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}
}
} 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<_>>();
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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)
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let wait_finished_fut = tokio::spawn(async move {
resp_stream.collect::<Vec<Result<_, _>>>().await;
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});
self.0.background.spawn(wait_finished_fut.map(|_| Ok(())));
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}
}
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if successes.len() >= quorum {
Ok(successes)
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} else {
let errors = errors.iter().map(|e| format!("{}", e)).collect::<Vec<_>>();
Err(Error::Quorum(quorum, successes.len(), to.len(), errors))
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}
}
}