v1.17: down samples outgoing gossip pull requests (backport of #33719)

gossip/benches/crds_gossip_pull.rs

@@ -52,6 +52,6 @@ fn bench_build_crds_filters(bencher: &mut Bencher) {
     let crds = RwLock::new(crds);
     bencher.iter(|| {
         let filters = crds_gossip_pull.build_crds_filters(&thread_pool, &crds, MAX_BLOOM_SIZE);
-        assert_eq!(filters.len(), 128);
+        assert_eq!(filters.len(), 16);
     });
 }

gossip/src/crds_gossip_pull.rs

@@ -53,8 +53,6 @@ use {
 pub const CRDS_GOSSIP_PULL_CRDS_TIMEOUT_MS: u64 = 15000;
 // Retention period of hashes of received outdated values.
 const FAILED_INSERTS_RETENTION_MS: u64 = 20_000;
-// Maximum number of pull requests to send out each time around.
-const MAX_NUM_PULL_REQUESTS: usize = 1024;
 pub const FALSE_RATE: f64 = 0.1f64;
 pub const KEYS: f64 = 8f64;
 
@@ -143,19 +141,26 @@ impl CrdsFilter {
 
 /// A vector of crds filters that together hold a complete set of Hashes.
 struct CrdsFilterSet {
-    filters: Vec<AtomicBloom<Hash>>,
+    filters: Vec<Option<AtomicBloom<Hash>>>,
     mask_bits: u32,
 }
 
 impl CrdsFilterSet {
-    fn new(num_items: usize, max_bytes: usize) -> Self {
+    fn new<R: Rng>(rng: &mut R, num_items: usize, max_bytes: usize) -> Self {
+        const SAMPLE_RATE: usize = 8;
+        const MAX_NUM_FILTERS: usize = 1024;
         let max_bits = (max_bytes * 8) as f64;
         let max_items = CrdsFilter::max_items(max_bits, FALSE_RATE, KEYS);
         let mask_bits = CrdsFilter::mask_bits(num_items as f64, max_items);
-        let filters =
-            repeat_with(|| Bloom::random(max_items as usize, FALSE_RATE, max_bits as usize).into())
-                .take(1 << mask_bits)
-                .collect();
+        let mut filters: Vec<_> = repeat_with(|| None).take(1usize << mask_bits).collect();
+        let mut indices: Vec<_> = (0..filters.len()).collect();
+        let size = (filters.len() + SAMPLE_RATE - 1) / SAMPLE_RATE;
+        for _ in 0..MAX_NUM_FILTERS.min(size) {
+            let k = rng.gen_range(0..indices.len());
+            let k = indices.swap_remove(k);
+            let filter = Bloom::random(max_items as usize, FALSE_RATE, max_bits as usize);
+            filters[k] = Some(AtomicBloom::<Hash>::from(filter));
+        }
         Self { filters, mask_bits }
     }
 
@@ -167,7 +172,9 @@ impl CrdsFilterSet {
                 .unwrap_or_default(),
         )
         .unwrap();
-        self.filters[index].add(&hash_value);
+        if let Some(filter) = &self.filters[index] {
+            filter.add(&hash_value);
+        }
     }
 }
 
@@ -177,10 +184,12 @@ impl From<CrdsFilterSet> for Vec<CrdsFilter> {
         cfs.filters
             .into_iter()
             .enumerate()
-            .map(|(seed, filter)| CrdsFilter {
-                filter: filter.into(),
-                mask: CrdsFilter::compute_mask(seed as u64, mask_bits),
-                mask_bits,
+            .filter_map(|(seed, filter)| {
+                Some(CrdsFilter {
+                    filter: Bloom::<Hash>::from(filter?),
+                    mask: CrdsFilter::compute_mask(seed as u64, mask_bits),
+                    mask_bits,
+                })
             })
             .collect()
     }
@@ -269,14 +278,7 @@ impl CrdsGossipPull {
         if nodes.is_empty() {
             return Err(CrdsGossipError::NoPeers);
         }
-        let mut filters = self.build_crds_filters(thread_pool, crds, bloom_size);
-        if filters.len() > MAX_NUM_PULL_REQUESTS {
-            for i in 0..MAX_NUM_PULL_REQUESTS {
-                let j = rng.gen_range(i..filters.len());
-                filters.swap(i, j);
-            }
-            filters.truncate(MAX_NUM_PULL_REQUESTS);
-        }
+        let filters = self.build_crds_filters(thread_pool, crds, bloom_size);
         // Associate each pull-request filter with a randomly selected peer.
         let dist = WeightedIndex::new(weights).unwrap();
         let nodes = repeat_with(|| nodes[dist.sample(&mut rng)].clone());
@@ -425,7 +427,7 @@ impl CrdsGossipPull {
         let crds = crds.read().unwrap();
         let num_items = crds.len() + crds.num_purged() + failed_inserts.len();
         let num_items = MIN_NUM_BLOOM_ITEMS.max(num_items);
-        let filters = CrdsFilterSet::new(num_items, bloom_size);
+        let filters = CrdsFilterSet::new(&mut rand::thread_rng(), num_items, bloom_size);
         thread_pool.install(|| {
             crds.par_values()
                 .with_min_len(PAR_MIN_LENGTH)
@@ -669,45 +671,61 @@ pub(crate) mod tests {
 
     #[test]
     fn test_crds_filter_set_add() {
-        let crds_filter_set =
-            CrdsFilterSet::new(/*num_items=*/ 9672788, /*max_bytes=*/ 8196);
-        let hash_values: Vec<_> = repeat_with(Hash::new_unique).take(1024).collect();
+        let mut rng = rand::thread_rng();
+        let crds_filter_set = CrdsFilterSet::new(
+            &mut rng, /*num_items=*/ 59672788, /*max_bytes=*/ 8196,
+        );
+        let hash_values: Vec<_> = repeat_with(|| {
+            let buf: [u8; 32] = rng.gen();
+            solana_sdk::hash::hashv(&[&buf])
+        })
+        .take(1024)
+        .collect();
+        assert_eq!(crds_filter_set.filters.len(), 8192);
         for hash_value in &hash_values {
             crds_filter_set.add(*hash_value);
         }
         let filters: Vec<CrdsFilter> = crds_filter_set.into();
+        let mut num_hits = 0;
         assert_eq!(filters.len(), 1024);
         for hash_value in hash_values {
-            let mut num_hits = 0;
+            let mut hit = false;
             let mut false_positives = 0;
             for filter in &filters {
                 if filter.test_mask(&hash_value) {
                     num_hits += 1;
+                    assert!(!hit);
+                    hit = true;
                     assert!(filter.contains(&hash_value));
                     assert!(filter.filter.contains(&hash_value));
                 } else if filter.filter.contains(&hash_value) {
                     false_positives += 1;
                 }
             }
-            assert_eq!(num_hits, 1);
             assert!(false_positives < 5);
         }
+        assert!(num_hits > 96, "num_hits: {num_hits}");
     }
 
     #[test]
     fn test_crds_filter_set_new() {
         // Validates invariances required by CrdsFilterSet::get in the
         // vector of filters generated by CrdsFilterSet::new.
-        let filters: Vec<CrdsFilter> =
-            CrdsFilterSet::new(/*num_items=*/ 55345017, /*max_bytes=*/ 4098).into();
-        assert_eq!(filters.len(), 16384);
+        let filters = CrdsFilterSet::new(
+            &mut rand::thread_rng(),
+            55345017, // num_items
+            4098,     // max_bytes
+        );
+        assert_eq!(filters.filters.len(), 16384);
+        let filters = Vec::<CrdsFilter>::from(filters);
+        assert_eq!(filters.len(), 1024);
         let mask_bits = filters[0].mask_bits;
         let right_shift = 64 - mask_bits;
         let ones = !0u64 >> mask_bits;
-        for (i, filter) in filters.iter().enumerate() {
+        for filter in &filters {
             // Check that all mask_bits are equal.
             assert_eq!(mask_bits, filter.mask_bits);
-            assert_eq!(i as u64, filter.mask >> right_shift);
+            assert!((0..16384).contains(&(filter.mask >> right_shift)));
             assert_eq!(ones, ones & filter.mask);
         }
     }
@@ -740,7 +758,7 @@ pub(crate) mod tests {
         let crds = RwLock::new(crds);
         assert!(num_inserts > 30_000, "num inserts: {num_inserts}");
         let filters = crds_gossip_pull.build_crds_filters(&thread_pool, &crds, MAX_BLOOM_SIZE);
-        assert_eq!(filters.len(), MIN_NUM_BLOOM_FILTERS.max(32));
+        assert_eq!(filters.len(), MIN_NUM_BLOOM_FILTERS.max(4));
         let crds = crds.read().unwrap();
         let purged: Vec<_> = thread_pool.install(|| crds.purged().collect());
         let hash_values: Vec<_> = crds.values().map(|v| v.value_hash).chain(purged).collect();
@@ -751,21 +769,24 @@ pub(crate) mod tests {
             "hash_values.len(): {}",
             hash_values.len()
         );
+        let mut num_hits = 0;
         let mut false_positives = 0;
         for hash_value in hash_values {
-            let mut num_hits = 0;
+            let mut hit = false;
             for filter in &filters {
                 if filter.test_mask(&hash_value) {
                     num_hits += 1;
+                    assert!(!hit);
+                    hit = true;
                     assert!(filter.contains(&hash_value));
                     assert!(filter.filter.contains(&hash_value));
                 } else if filter.filter.contains(&hash_value) {
                     false_positives += 1;
                 }
             }
-            assert_eq!(num_hits, 1);
         }
-        assert!(false_positives < 150_000, "fp: {false_positives}");
+        assert!(num_hits > 4000, "num_hits: {num_hits}");
+        assert!(false_positives < 20_000, "fp: {false_positives}");
     }
 
     #[test]
@@ -1308,7 +1329,8 @@ pub(crate) mod tests {
     }
     #[test]
     fn test_crds_filter_complete_set_add_mask() {
-        let mut filters: Vec<CrdsFilter> = CrdsFilterSet::new(1000, 10).into();
+        let mut filters =
+            Vec::<CrdsFilter>::from(CrdsFilterSet::new(&mut rand::thread_rng(), 1000, 10));
         assert!(filters.iter().all(|f| f.mask_bits > 0));
         let mut h: Hash = Hash::default();
         // rev to make the hash::default() miss on the first few test_masks