From f47d6402c34de34c2d20d6165cfd26f423dfb7b1 Mon Sep 17 00:00:00 2001
From: Christien Rioux <chris@veilid.org>
Date: Tue, 31 Oct 2023 15:39:00 -0400
Subject: [PATCH] staggered pings

---
 .../src/routing_table/tasks/ping_validator.rs | 57 ++++++++++++++-----
 1 file changed, 43 insertions(+), 14 deletions(-)

diff --git a/veilid-core/src/routing_table/tasks/ping_validator.rs b/veilid-core/src/routing_table/tasks/ping_validator.rs
index 7a3070d0..fdd54087 100644
--- a/veilid-core/src/routing_table/tasks/ping_validator.rs
+++ b/veilid-core/src/routing_table/tasks/ping_validator.rs
@@ -4,6 +4,9 @@ use super::*;
 /// remains valid, as well as to make sure we remain in any relay node's routing table
 const KEEPALIVE_PING_INTERVAL_SECS: u32 = 10;
 
+/// Ping queue processing depth
+const MAX_PARALLEL_PINGS: usize = 16;
+
 use futures_util::stream::{FuturesUnordered, StreamExt};
 use futures_util::FutureExt;
 use stop_token::future::FutureExt as StopFutureExt;
@@ -14,12 +17,12 @@ type PingValidatorFuture =
 impl RoutingTable {
     // Ping each node in the routing table if they need to be pinged
     // to determine their reliability
-    #[instrument(level = "trace", skip(self), err)]
+    #[instrument(level = "trace", skip(self, futurequeue), err)]
     async fn relay_keepalive_public_internet(
         &self,
         cur_ts: Timestamp,
         relay_nr: NodeRef,
-        unord: &mut FuturesUnordered<PingValidatorFuture>,
+        futurequeue: &mut VecDeque<PingValidatorFuture>,
     ) -> EyreResult<()> {
         let rpc = self.rpc_processor();
         // Get our publicinternet dial info
@@ -107,7 +110,7 @@ impl RoutingTable {
             #[cfg(not(feature = "network-result-extra"))]
             log_rtab!("--> Keepalive ping to {:?}", relay_nr_filtered);
 
-            unord.push(
+            futurequeue.push_back(
                 async move {
                     rpc.rpc_call_status(Destination::direct(relay_nr_filtered), true)
                         .await
@@ -120,11 +123,11 @@ impl RoutingTable {
     }
     // Ping each node in the routing table if they need to be pinged
     // to determine their reliability
-    #[instrument(level = "trace", skip(self), err)]
+    #[instrument(level = "trace", skip(self, futurequeue), err)]
     async fn ping_validator_public_internet(
         &self,
         cur_ts: Timestamp,
-        unord: &mut FuturesUnordered<PingValidatorFuture>,
+        futurequeue: &mut VecDeque<PingValidatorFuture>,
     ) -> EyreResult<()> {
         let rpc = self.rpc_processor();
 
@@ -136,7 +139,7 @@ impl RoutingTable {
 
         // If this is our relay, let's check for NAT keepalives
         if let Some(relay_nr) = opt_relay_nr {
-            self.relay_keepalive_public_internet(cur_ts, relay_nr, unord)
+            self.relay_keepalive_public_internet(cur_ts, relay_nr, futurequeue)
                 .await?;
         }
 
@@ -144,7 +147,7 @@ impl RoutingTable {
         for nr in node_refs {
             let rpc = rpc.clone();
             log_rtab!("--> Validator ping to {:?}", nr);
-            unord.push(
+            futurequeue.push_back(
                 async move { rpc.rpc_call_status(Destination::direct(nr), false).await }
                     .instrument(Span::current())
                     .boxed(),
@@ -156,11 +159,11 @@ impl RoutingTable {
 
     // Ping each node in the LocalNetwork routing domain if they
     // need to be pinged to determine their reliability
-    #[instrument(level = "trace", skip(self), err)]
+    #[instrument(level = "trace", skip(self, futurequeue), err)]
     async fn ping_validator_local_network(
         &self,
         cur_ts: Timestamp,
-        unord: &mut FuturesUnordered<PingValidatorFuture>,
+        futurequeue: &mut VecDeque<PingValidatorFuture>,
     ) -> EyreResult<()> {
         let rpc = self.rpc_processor();
 
@@ -172,7 +175,7 @@ impl RoutingTable {
             let rpc = rpc.clone();
 
             // Just do a single ping with the best protocol for all the nodes
-            unord.push(
+            futurequeue.push_back(
                 async move { rpc.rpc_call_status(Destination::direct(nr), false).await }
                     .instrument(Span::current())
                     .boxed(),
@@ -191,18 +194,44 @@ impl RoutingTable {
         _last_ts: Timestamp,
         cur_ts: Timestamp,
     ) -> EyreResult<()> {
-        let mut unord = FuturesUnordered::new();
+        let mut futurequeue: VecDeque<PingValidatorFuture> = VecDeque::new();
 
         // PublicInternet
-        self.ping_validator_public_internet(cur_ts, &mut unord)
+        self.ping_validator_public_internet(cur_ts, &mut futurequeue)
             .await?;
 
         // LocalNetwork
-        self.ping_validator_local_network(cur_ts, &mut unord)
+        self.ping_validator_local_network(cur_ts, &mut futurequeue)
             .await?;
 
         // Wait for ping futures to complete in parallel
-        while let Ok(Some(_)) = unord.next().timeout_at(stop_token.clone()).await {}
+        let mut unord = FuturesUnordered::new();
+
+        while !unord.is_empty() || !futurequeue.is_empty() {
+            #[cfg(feature = "verbose-tracing")]
+            log_rtab!(debug "Ping validation queue: {} remaining, {} in progress", futurequeue.len(), unord.len());
+            // Process one unordered futures if we have some
+            match unord.next().timeout_at(stop_token.clone()).await {
+                Ok(Some(_)) => {
+                    // Some ping completed
+                }
+                Ok(None) => {
+                    // We're empty
+                }
+                Err(_) => {
+                    // Timeout means we drop the rest because we were asked to stop
+                    break;
+                }
+            }
+
+            // Fill unord up to max parallelism
+            while unord.len() < MAX_PARALLEL_PINGS {
+                let Some(fq) = futurequeue.pop_front() else {
+                    break;
+                };
+                unord.push(fq);
+            }
+        }
 
         Ok(())
     }