Track time diff between new_payload and FCU

crates/rpc/rpc-engine-api/Cargo.toml

@@ -45,6 +45,7 @@ jsonrpsee-types.workspace = true
 serde.workspace = true
 thiserror.workspace = true
 tracing.workspace = true
+parking_lot.workspace = true
 
 [dev-dependencies]
 reth-ethereum-engine-primitives.workspace = true

crates/rpc/rpc-engine-api/src/engine_api.rs

@@ -10,6 +10,7 @@ use alloy_rpc_types_engine::{
 };
 use async_trait::async_trait;
 use jsonrpsee_core::RpcResult;
+use parking_lot::Mutex;
 use reth_beacon_consensus::BeaconConsensusEngineHandle;
 use reth_chainspec::{EthereumHardforks, Hardforks};
 use reth_engine_primitives::{EngineTypes, EngineValidator};
@@ -67,6 +68,8 @@ struct EngineApiInner<Provider, EngineT: EngineTypes, Pool, Validator, ChainSpec
     tx_pool: Pool,
     /// Engine validator.
     validator: Validator,
+    /// Start time of the latest payload request
+    latest_new_payload_response: Mutex<Option<Instant>>,
 }
 
 impl<Provider, EngineT, Pool, Validator, ChainSpec>
@@ -102,6 +105,7 @@ where
             capabilities,
             tx_pool,
             validator,
+            latest_new_payload_response: Mutex::new(None),
         });
         Self { inner }
     }
@@ -140,11 +144,13 @@ where
         self.inner
             .validator
             .validate_version_specific_fields(EngineApiMessageVersion::V1, payload_or_attrs)?;
+
         Ok(self
             .inner
             .beacon_consensus
             .new_payload(payload, ExecutionPayloadSidecar::none())
-            .await?)
+            .await
+            .inspect(|_| self.inner.on_new_payload_response())?)
     }
 
     /// See also <https://github.com/ethereum/execution-apis/blob/584905270d8ad665718058060267061ecfd79ca5/src/engine/shanghai.md#engine_newpayloadv2>
@@ -164,7 +170,8 @@ where
             .inner
             .beacon_consensus
             .new_payload(payload, ExecutionPayloadSidecar::none())
-            .await?)
+            .await
+            .inspect(|_| self.inner.on_new_payload_response())?)
     }
 
     /// See also <https://github.com/ethereum/execution-apis/blob/fe8e13c288c592ec154ce25c534e26cb7ce0530d/src/engine/cancun.md#engine_newpayloadv3>
@@ -194,7 +201,8 @@ where
                     parent_beacon_block_root,
                 }),
             )
-            .await?)
+            .await
+            .inspect(|_| self.inner.on_new_payload_response())?)
     }
 
     /// See also <https://github.com/ethereum/execution-apis/blob/7907424db935b93c2fe6a3c0faab943adebe8557/src/engine/prague.md#engine_newpayloadv4>
@@ -225,7 +233,8 @@ where
                     execution_requests,
                 ),
             )
-            .await?)
+            .await
+            .inspect(|_| self.inner.on_new_payload_response())?)
     }
 
     /// Sends a message to the beacon consensus engine to update the fork choice _without_
@@ -598,6 +607,8 @@ where
         state: ForkchoiceState,
         payload_attrs: Option<EngineT::PayloadAttributes>,
     ) -> EngineApiResult<ForkchoiceUpdated> {
+        self.inner.record_elapsed_time_on_fcu();
+
         if let Some(ref attrs) = payload_attrs {
             let attr_validation_res =
                 self.inner.validator.ensure_well_formed_attributes(version, attrs);
@@ -631,6 +642,26 @@ where
     }
 }
 
+impl<Provider, EngineT, Pool, Validator, ChainSpec>
+    EngineApiInner<Provider, EngineT, Pool, Validator, ChainSpec>
+where
+    EngineT: EngineTypes,
+{
+    /// Tracks the elapsed time between the new payload response and the received forkchoice update
+    /// request.
+    fn record_elapsed_time_on_fcu(&self) {
+        if let Some(start_time) = self.latest_new_payload_response.lock().take() {
+            let elapsed_time = start_time.elapsed();
+            self.metrics.latency.new_payload_forkchoice_updated_time_diff.record(elapsed_time);
+        }
+    }
+
+    /// Updates the timestamp for the latest new payload response.
+    fn on_new_payload_response(&self) {
+        self.latest_new_payload_response.lock().replace(Instant::now());
+    }
+}
+
 #[async_trait]
 impl<Provider, EngineT, Pool, Validator, ChainSpec> EngineApiServer<EngineT>
     for EngineApi<Provider, EngineT, Pool, Validator, ChainSpec>

crates/rpc/rpc-engine-api/src/metrics.rs

@@ -34,6 +34,8 @@ pub(crate) struct EngineApiLatencyMetrics {
     pub(crate) fork_choice_updated_v2: Histogram,
     /// Latency for `engine_forkchoiceUpdatedV3`
     pub(crate) fork_choice_updated_v3: Histogram,
+    /// Time diff between `engine_newPayloadV*` and the next FCU
+    pub(crate) new_payload_forkchoice_updated_time_diff: Histogram,
     /// Latency for `engine_getPayloadV1`
     pub(crate) get_payload_v1: Histogram,
     /// Latency for `engine_getPayloadV2`