Metric for hdiff sizes

michaelsproul · michaelsproul · commit 9c8e58cc704a · 2025-06-13T17:16:27.000+10:00
diff --git a/beacon_node/store/src/hdiff.rs b/beacon_node/store/src/hdiff.rs
@@ -649,6 +649,10 @@ impl HierarchyConfig {
             Err(Error::InvalidHierarchy)
         }
     }
+
+    pub fn exponent_for_slot(slot: Slot) -> u32 {
+        slot.as_u64().trailing_zeros()
+    }
 }
 
 impl HierarchyModuli {
diff --git a/beacon_node/store/src/hot_cold_store.rs b/beacon_node/store/src/hot_cold_store.rs
@@ -1,7 +1,7 @@
 use crate::config::{OnDiskStoreConfig, StoreConfig};
 use crate::database::interface::BeaconNodeBackend;
 use crate::forwards_iter::{HybridForwardsBlockRootsIterator, HybridForwardsStateRootsIterator};
-use crate::hdiff::{HDiff, HDiffBuffer, HierarchyModuli, StorageStrategy};
+use crate::hdiff::{HDiff, HDiffBuffer, HierarchyConfig, HierarchyModuli, StorageStrategy};
 use crate::historic_state_cache::HistoricStateCache;
 use crate::iter::{BlockRootsIterator, ParentRootBlockIterator, RootsIterator};
 use crate::memory_store::MemoryStore;
@@ -1588,6 +1588,12 @@ impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotColdDB<E, Hot, Cold>
             HDiff::compute(&base_buffer, &target_buffer, &self.config)?
         };
         let diff_bytes = diff.as_ssz_bytes();
+        let layer = HierarchyConfig::exponent_for_slot(state.slot());
+        metrics::observe_vec(
+            &metrics::BEACON_HDIFF_SIZES,
+            &[&layer.to_string()],
+            diff_bytes.len() as f64,
+        );
         ops.push(KeyValueStoreOp::PutKeyValue(
             DBColumn::BeaconStateHotDiff,
             state_root.as_slice().to_vec(),
@@ -2038,6 +2044,12 @@ impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotColdDB<E, Hot, Cold>
             HDiff::compute(&base_buffer, &target_buffer, &self.config)?
         };
         let diff_bytes = diff.as_ssz_bytes();
+        let layer = HierarchyConfig::exponent_for_slot(state.slot());
+        metrics::observe_vec(
+            &metrics::BEACON_HDIFF_SIZES,
+            &[&layer.to_string()],
+            diff_bytes.len() as f64,
+        );
 
         ops.push(KeyValueStoreOp::PutKeyValue(
             DBColumn::BeaconStateDiff,
diff --git a/beacon_node/store/src/metrics.rs b/beacon_node/store/src/metrics.rs
@@ -209,6 +209,24 @@ pub static BEACON_HDIFF_BUFFER_APPLY_RESIZES: LazyLock<Result<Histogram>> = Lazy
         Ok(vec![0.0, 1.0, 2.0, 3.0, 4.0, 5.0])
     )
 });
+// This metric is not split hot/cold because both databases use the same hierarchy config anyway
+// and that's all that affects diff sizes.
+pub static BEACON_HDIFF_SIZES: LazyLock<Result<HistogramVec>> = LazyLock::new(|| {
+    try_create_histogram_vec_with_buckets(
+        "store_hdiff_sizes",
+        "Size of hdiffs in bytes by layer (exponent)",
+        Ok(vec![
+            0.0,
+            2_000.0,
+            20_000.0,
+            200_000.0,
+            500_000.0,
+            2_000_000.0,
+            10_000_000.0,
+        ]),
+        &["exponent"],
+    )
+});
 /*
  * Beacon Block
  */

Original file line number	Diff line number	Diff line change
`@@ -649,6 +649,10 @@ impl HierarchyConfig {`
`649`	`649`	`Err(Error::InvalidHierarchy)`
`650`	`650`	`}`
`651`	`651`	`}`
	`652`	`+`
	`653`	`+ pub fn exponent_for_slot(slot: Slot) -> u32 {`
	`654`	`+ slot.as_u64().trailing_zeros()`
	`655`	`+ }`
`652`	`656`	`}`
`653`	`657`
`654`	`658`	`impl HierarchyModuli {`