feat: block selection policy

src/cli.rs

@@ -8,7 +8,7 @@ use tokio::signal::unix::{SignalKind, signal as unix_signal};
 use tracing::{Level, info};
 
 use crate::{
-    DebugClient, ProxyLayer, RollupBoostServer, RpcClient,
+    BlockSelectionPolicy, DebugClient, ProxyLayer, RollupBoostServer, RpcClient,
     client::rpc::{BuilderArgs, L2ClientArgs},
     debug_api::ExecutionMode,
     init_metrics, init_tracing,
@@ -87,6 +87,9 @@ pub struct Args {
     /// Execution mode to start rollup boost with
     #[arg(long, env, default_value = "enabled")]
     pub execution_mode: ExecutionMode,
+
+    #[arg(long, env)]
+    pub block_selection_policy: Option<BlockSelectionPolicy>,
 }
 
 impl Args {
@@ -160,6 +163,7 @@ impl Args {
             l2_client,
             builder_client,
             self.execution_mode,
+            self.block_selection_policy,
             probes,
             self.health_check_interval,
             self.max_unsafe_interval,

src/lib.rs

@@ -30,3 +30,6 @@ pub use health::*;
 
 mod payload;
 pub use payload::*;
+
+mod selection;
+pub use selection::*;

src/payload.rs

@@ -22,6 +22,27 @@ impl OpExecutionPayloadEnvelope {
             OpExecutionPayloadEnvelope::V4(_) => PayloadVersion::V4,
         }
     }
+
+    pub fn gas_used(&self) -> u64 {
+        match self {
+            OpExecutionPayloadEnvelope::V3(payload) => {
+                payload
+                    .execution_payload
+                    .payload_inner
+                    .payload_inner
+                    .gas_used
+            }
+
+            OpExecutionPayloadEnvelope::V4(payload) => {
+                payload
+                    .execution_payload
+                    .payload_inner
+                    .payload_inner
+                    .payload_inner
+                    .gas_used
+            }
+        }
+    }
 }
 
 impl From<OpExecutionPayloadEnvelope> for ExecutionPayload {
@@ -107,7 +128,7 @@ impl PayloadVersion {
     }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum PayloadSource {
     L2,
     Builder,

src/selection.rs

@@ -0,0 +1,109 @@
+use crate::{OpExecutionPayloadEnvelope, PayloadSource};
+use serde::{Deserialize, Serialize};
+
+/// Defines the strategy for choosing between the builder block and the L2 client block
+/// during block production.
+#[derive(Serialize, Deserialize, Debug, Copy, Clone, PartialEq, clap::ValueEnum)]
+pub enum BlockSelectionPolicy {
+    /// Selects the block based on gas usage.
+    ///
+    /// If the builder block uses less than 10% of the gas used by the L2 client block,
+    /// the L2 block is selected instead. This prevents propagation of valid but empty
+    /// builder blocks and mitigates issues where the builder is not receiving enough
+    /// transactions due to networking or peering failures.
+    GasUsed,
+}
+
+impl BlockSelectionPolicy {
+    pub fn select_block(
+        &self,
+        builder_payload: OpExecutionPayloadEnvelope,
+        l2_payload: OpExecutionPayloadEnvelope,
+    ) -> (OpExecutionPayloadEnvelope, PayloadSource) {
+        match self {
+            BlockSelectionPolicy::GasUsed => {
+                let builder_gas = builder_payload.gas_used() as f64;
+                let l2_gas = l2_payload.gas_used() as f64;
+
+                // Select the L2 block if the builder block uses less than 10% of the gas.
+                // This avoids selecting empty or severely underfilled blocks,
+                if builder_gas < l2_gas * 0.1 {
+                    (l2_payload, PayloadSource::L2)
+                } else {
+                    (builder_payload, PayloadSource::Builder)
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use op_alloy_rpc_types_engine::OpExecutionPayloadEnvelopeV4;
+
+    #[test]
+    fn test_gas_used_policy_select_l2_block() -> eyre::Result<()> {
+        let execution_payload = r#"{"executionPayload":{"parentHash":"0xe927a1448525fb5d32cb50ee1408461a945ba6c39bd5cf5621407d500ecc8de9","feeRecipient":"0x0000000000000000000000000000000000000000","stateRoot":"0x10f8a0830000e8edef6d00cc727ff833f064b1950afd591ae41357f97e543119","receiptsRoot":"0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421","logsBloom":"0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000","prevRandao":"0xe0d8b4521a7da1582a713244ffb6a86aa1726932087386e2dc7973f43fc6cb24","blockNumber":"0x1","gasLimit":"0x2ffbd2","gasUsed":"0x0","timestamp":"0x1235","extraData":"0xd883010d00846765746888676f312e32312e30856c696e7578","baseFeePerGas":"0x342770c0","blockHash":"0x44d0fa5f2f73a938ebb96a2a21679eb8dea3e7b7dd8fd9f35aa756dda8bf0a8a","transactions":[],"withdrawals":[],"blobGasUsed":"0x0","excessBlobGas":"0x0","withdrawalsRoot":"0x123400000000000000000000000000000000000000000000000000000000babe"},"blockValue":"0x0","blobsBundle":{"commitments":[],"proofs":[],"blobs":[]},"shouldOverrideBuilder":false,"parentBeaconBlockRoot":"0xdead00000000000000000000000000000000000000000000000000000000beef","executionRequests":["0xdeadbeef"]}"#;
+        let mut builder_payload: OpExecutionPayloadEnvelopeV4 =
+            serde_json::from_str(execution_payload)?;
+        let mut l2_payload = builder_payload.clone();
+
+        let gas_used = 1000000000;
+        l2_payload
+            .execution_payload
+            .payload_inner
+            .payload_inner
+            .payload_inner
+            .gas_used = gas_used;
+
+        builder_payload
+            .execution_payload
+            .payload_inner
+            .payload_inner
+            .payload_inner
+            .gas_used = (gas_used as f64 * 0.09) as u64;
+
+        let builder_payload = OpExecutionPayloadEnvelope::V4(builder_payload);
+        let l2_payload = OpExecutionPayloadEnvelope::V4(l2_payload);
+
+        let selected_payload =
+            BlockSelectionPolicy::GasUsed.select_block(builder_payload, l2_payload);
+
+        assert_eq!(selected_payload.1, PayloadSource::L2);
+        Ok(())
+    }
+
+    #[test]
+    fn test_gas_used_policy_select_builder_block() -> eyre::Result<()> {
+        let execution_payload = r#"{"executionPayload":{"parentHash":"0xe927a1448525fb5d32cb50ee1408461a945ba6c39bd5cf5621407d500ecc8de9","feeRecipient":"0x0000000000000000000000000000000000000000","stateRoot":"0x10f8a0830000e8edef6d00cc727ff833f064b1950afd591ae41357f97e543119","receiptsRoot":"0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421","logsBloom":"0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000","prevRandao":"0xe0d8b4521a7da1582a713244ffb6a86aa1726932087386e2dc7973f43fc6cb24","blockNumber":"0x1","gasLimit":"0x2ffbd2","gasUsed":"0x0","timestamp":"0x1235","extraData":"0xd883010d00846765746888676f312e32312e30856c696e7578","baseFeePerGas":"0x342770c0","blockHash":"0x44d0fa5f2f73a938ebb96a2a21679eb8dea3e7b7dd8fd9f35aa756dda8bf0a8a","transactions":[],"withdrawals":[],"blobGasUsed":"0x0","excessBlobGas":"0x0","withdrawalsRoot":"0x123400000000000000000000000000000000000000000000000000000000babe"},"blockValue":"0x0","blobsBundle":{"commitments":[],"proofs":[],"blobs":[]},"shouldOverrideBuilder":false,"parentBeaconBlockRoot":"0xdead00000000000000000000000000000000000000000000000000000000beef","executionRequests":["0xdeadbeef"]}"#;
+        let mut builder_payload: OpExecutionPayloadEnvelopeV4 =
+            serde_json::from_str(execution_payload)?;
+        let mut l2_payload = builder_payload.clone();
+
+        let gas_used = 1000000000;
+        l2_payload
+            .execution_payload
+            .payload_inner
+            .payload_inner
+            .payload_inner
+            .gas_used = gas_used;
+
+        builder_payload
+            .execution_payload
+            .payload_inner
+            .payload_inner
+            .payload_inner
+            .gas_used = (gas_used as f64 * 0.1) as u64;
+
+        let builder_payload = OpExecutionPayloadEnvelope::V4(builder_payload);
+        let l2_payload = OpExecutionPayloadEnvelope::V4(l2_payload);
+
+        let selected_payload =
+            BlockSelectionPolicy::GasUsed.select_block(builder_payload, l2_payload);
+
+        assert_eq!(selected_payload.1, PayloadSource::Builder);
+        Ok(())
+    }
+}

src/server.rs

@@ -1,3 +1,4 @@
+use crate::BlockSelectionPolicy;
 use crate::debug_api::ExecutionMode;
 use crate::{
     HealthHandle,
@@ -35,6 +36,7 @@ pub struct RollupBoostServer {
     pub l2_client: Arc<RpcClient>,
     pub builder_client: Arc<RpcClient>,
     pub payload_trace_context: Arc<PayloadTraceContext>,
+    block_selection_policy: Option<BlockSelectionPolicy>,
     health_handle: JoinHandle<()>,
     execution_mode: Arc<Mutex<ExecutionMode>>,
     probes: Arc<Probes>,
@@ -45,6 +47,7 @@ impl RollupBoostServer {
         l2_client: RpcClient,
         builder_client: RpcClient,
         initial_execution_mode: ExecutionMode,
+        block_selection_policy: Option<BlockSelectionPolicy>,
         probes: Arc<Probes>,
         health_check_interval: u64,
         max_unsafe_interval: u64,
@@ -60,6 +63,7 @@ impl RollupBoostServer {
         Self {
             l2_client: Arc::new(l2_client),
             builder_client: Arc::new(builder_client),
+            block_selection_policy,
             payload_trace_context: Arc::new(PayloadTraceContext::new()),
             execution_mode: Arc::new(Mutex::new(initial_execution_mode)),
             probes,
@@ -178,13 +182,15 @@ impl RollupBoostServer {
                 l2_payload.inspect_err(|_| self.probes.set_health(Health::ServiceUnavailable))?;
             self.probes.set_health(Health::Healthy);
 
-            if let Ok(Some(payload)) = builder_payload {
+            if let Ok(Some(builder_payload)) = builder_payload {
                 // If execution mode is set to DryRun, fallback to the l2_payload,
                 // otherwise prefer the builder payload
                 if self.execution_mode().is_dry_run() {
                     (l2_payload, PayloadSource::L2)
+                } else if let Some(selection_policy) = &self.block_selection_policy {
+                    selection_policy.select_block(builder_payload, l2_payload)
                 } else {
-                    (payload, PayloadSource::Builder)
+                    (builder_payload, PayloadSource::Builder)
                 }
             } else {
                 // Only update the health status if the builder payload fails
@@ -600,6 +606,7 @@ mod tests {
                 l2_client,
                 builder_client,
                 ExecutionMode::Enabled,
+                None,
                 probes,
                 60,
                 5,