garage/src/rpc/rpc_helper.rs

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//! Contain structs related to making RPCs
use std::sync::Arc;
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use std::time::Duration;
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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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use opentelemetry::KeyValue;
use opentelemetry::{
trace::{FutureExt as OtelFutureExt, Span, TraceContextExt, Tracer},
Context,
};
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pub use netapp::endpoint::{Endpoint, EndpointHandler, StreamingEndpointHandler};
use netapp::message::IntoReq;
pub use netapp::message::{
Message as Rpc, OrderTag, Req, RequestPriority, Resp, PRIO_BACKGROUND, PRIO_HIGH, PRIO_NORMAL,
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};
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use netapp::peering::fullmesh::FullMeshPeeringStrategy;
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pub use netapp::{self, NetApp, NodeID};
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use garage_util::background::BackgroundRunner;
use garage_util::data::*;
use garage_util::error::Error;
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use garage_util::metrics::RecordDuration;
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use crate::metrics::RpcMetrics;
use crate::ring::Ring;
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const DEFAULT_TIMEOUT: Duration = Duration::from_secs(10);
// Don't allow more than 100 concurrent outgoing RPCs.
const MAX_CONCURRENT_REQUESTS: usize = 100;
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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>>,
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request_buffer_semaphore: Arc<Semaphore>,
metrics: RpcMetrics,
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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 {
let sem = Arc::new(Semaphore::new(MAX_CONCURRENT_REQUESTS));
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let metrics = RpcMetrics::new(sem.clone());
Self(Arc::new(RpcHelperInner {
our_node_id,
fullmesh,
background,
ring,
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request_buffer_semaphore: sem,
metrics,
}))
}
pub async fn call<M, N, H, S>(
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&self,
endpoint: &Endpoint<M, H>,
to: Uuid,
msg: N,
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strat: RequestStrategy,
) -> Result<S, Error>
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where
M: Rpc<Response = Result<S, Error>>,
N: IntoReq<M> + Send,
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H: StreamingEndpointHandler<M>,
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{
let metric_tags = [
KeyValue::new("rpc_endpoint", endpoint.path().to_string()),
KeyValue::new("from", format!("{:?}", self.0.our_node_id)),
KeyValue::new("to", format!("{:?}", to)),
];
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let permit = self
.0
.request_buffer_semaphore
.acquire()
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.record_duration(&self.0.metrics.rpc_queueing_time, &metric_tags)
.await?;
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self.0.metrics.rpc_counter.add(1, &metric_tags);
let node_id = to.into();
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let rpc_call = endpoint
.call_streaming(&node_id, msg, strat.rs_priority)
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.record_duration(&self.0.metrics.rpc_duration, &metric_tags);
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select! {
res = rpc_call => {
drop(permit);
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if res.is_err() {
self.0.metrics.rpc_netapp_error_counter.add(1, &metric_tags);
}
let res = res?.into_msg();
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if res.is_err() {
self.0.metrics.rpc_garage_error_counter.add(1, &metric_tags);
}
Ok(res?)
}
_ = tokio::time::sleep(strat.rs_timeout) => {
drop(permit);
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self.0.metrics.rpc_timeout_counter.add(1, &metric_tags);
Err(Error::Timeout)
}
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}
}
pub async fn call_many<M, N, H, S>(
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&self,
endpoint: &Endpoint<M, H>,
to: &[Uuid],
msg: N,
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strat: RequestStrategy,
) -> Result<Vec<(Uuid, Result<S, Error>)>, Error>
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where
M: Rpc<Response = Result<S, Error>>,
N: IntoReq<M>,
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H: StreamingEndpointHandler<M>,
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{
let msg = msg.into_req().map_err(netapp::error::Error::from)?;
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let resps = join_all(
to.iter()
.map(|to| self.call(endpoint, *to, msg.clone(), strat)),
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)
.await;
Ok(to
.iter()
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.cloned()
.zip(resps.into_iter())
.collect::<Vec<_>>())
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}
pub async fn broadcast<M, N, H, S>(
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&self,
endpoint: &Endpoint<M, H>,
msg: N,
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strat: RequestStrategy,
) -> Result<Vec<(Uuid, Result<S, Error>)>, Error>
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where
M: Rpc<Response = Result<S, Error>>,
N: IntoReq<M>,
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H: StreamingEndpointHandler<M>,
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{
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
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pub async fn try_call_many<M, N, H, S>(
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&self,
endpoint: &Arc<Endpoint<M, H>>,
to: &[Uuid],
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msg: N,
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strategy: RequestStrategy,
) -> Result<Vec<S>, Error>
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where
M: Rpc<Response = Result<S, Error>> + 'static,
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N: IntoReq<M>,
H: StreamingEndpointHandler<M> + 'static,
S: Send + 'static,
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{
let quorum = strategy.rs_quorum.unwrap_or(to.len());
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let tracer = opentelemetry::global::tracer("garage");
let span_name = if strategy.rs_interrupt_after_quorum {
format!("RPC {} to {} of {}", endpoint.path(), quorum, to.len())
} else {
format!(
"RPC {} to {} (quorum {})",
endpoint.path(),
to.len(),
quorum
)
};
let mut span = tracer.start(span_name);
span.set_attribute(KeyValue::new("from", format!("{:?}", self.0.our_node_id)));
span.set_attribute(KeyValue::new("to", format!("{:?}", to)));
span.set_attribute(KeyValue::new("quorum", quorum as i64));
span.set_attribute(KeyValue::new(
"interrupt_after_quorum",
strategy.rs_interrupt_after_quorum.to_string(),
));
self.try_call_many_internal(endpoint, to, msg, strategy, quorum)
.with_context(Context::current_with_span(span))
.await
}
async fn try_call_many_internal<M, N, H, S>(
&self,
endpoint: &Arc<Endpoint<M, H>>,
to: &[Uuid],
msg: N,
strategy: RequestStrategy,
quorum: usize,
) -> Result<Vec<S>, Error>
where
M: Rpc<Response = Result<S, Error>> + 'static,
N: IntoReq<M>,
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H: StreamingEndpointHandler<M> + 'static,
S: Send + 'static,
{
let msg = msg.into_req().map_err(netapp::error::Error::from)?;
// 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(&endpoint2, to, msg, strategy).await
})
});
// 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.
// Reorder requests to priorize closeness / low latency
let request_order = self.request_order(to);
let mut ord_requests = vec![(); request_order.len()]
.into_iter()
.map(|_| None)
.collect::<Vec<_>>();
for (to, fut) in requests {
let i = request_order.iter().position(|x| *x == to).unwrap();
ord_requests[i] = Some((to, fut));
}
// Make an iterator to take requests in their sorted order
let mut requests = ord_requests.into_iter().map(Option::unwrap);
// 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((req_to, fut)) = requests.next() {
let tracer = opentelemetry::global::tracer("garage");
let span = tracer.start(format!("RPC to {:?}", req_to));
resp_stream.push(tokio::spawn(
fut.with_context(Context::current_with_span(span)),
));
} 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().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<_>>();
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);
}
}
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}
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(())));
}
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}
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))
}
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}
pub fn request_order(&self, nodes: &[Uuid]) -> Vec<Uuid> {
// 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.layout.node_role(&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 nodes = nodes
.iter()
.map(|to| {
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let peer_zone = match ring.layout.node_role(to) {
Some(pc) => &pc.zone,
None => "",
};
let peer_avg_ping = peer_list
.iter()
.find(|x| x.id.as_ref() == to.as_slice())
.and_then(|pi| pi.avg_ping)
.unwrap_or_else(|| Duration::from_secs(1));
(
*to != self.0.our_node_id,
peer_zone != our_zone,
peer_avg_ping,
*to,
)
})
.collect::<Vec<_>>();
// Sort requests by (priorize ourself, priorize same zone, priorize low latency)
nodes.sort_by_key(|(diffnode, diffzone, ping, _to)| (*diffnode, *diffzone, *ping));
nodes
.into_iter()
.map(|(_, _, _, to)| to)
.collect::<Vec<_>>()
}
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}