Add support for multiple builder and block selection

Cargo.toml

@@ -28,6 +28,7 @@ hyper-util = { version = "0.1", features = ["full"] }
 serde_json = "1.0.96"
 reth-rpc-layer = { git = "https://github.com/paradigmxyz/reth.git", tag = "v1.0.7" }
 reth-optimism-payload-builder = { git = "https://github.com/paradigmxyz/reth.git", tag = "v1.0.7", features = ["optimism"] }
+futures = "0.3.31"
 
 [dev-dependencies]
 anyhow = "1.0"

src/main.rs

@@ -18,6 +18,7 @@ use tracing_subscriber::EnvFilter;
 mod error;
 mod proxy;
 mod server;
+mod selector;
 
 #[derive(Parser, Debug)]
 #[clap(author, version, about)]
@@ -45,7 +46,7 @@ struct Args {
 
     /// URL of the builder execution engine
     #[arg(long, env)]
-    builder_url: String,
+    builder_urls: Vec<String>,
 
     /// Use the proposer to sync the builder node
     #[arg(long, env, default_value = "false")]
@@ -112,12 +113,12 @@ async fn main() -> Result<()> {
     // Initialize the l2 client
     let l2_client = create_client(&args.l2_url, jwt_secret)?;
 
-    // Initialize the builder client
-    let builder_client = create_client(&args.builder_url, builder_jwt_secret)?;
+    // Initialize the builder clients
+    let builder_clients = args.builder_urls.iter().map(|url| create_client(url, builder_jwt_secret)).collect::<Result<Vec<_>>>()?;
 
     let eth_engine_api = EthEngineApi::new(
         Arc::new(l2_client),
-        Arc::new(builder_client),
+        builder_clients.iter().map(|c| Arc::new(c.clone())).collect(),
         args.boost_sync,
     );
     let mut module: RpcModule<()> = RpcModule::new(());

src/selector.rs

@@ -0,0 +1,28 @@
+use jsonrpsee::core::ClientError;
+use op_alloy_rpc_types_engine::OptimismExecutionPayloadEnvelopeV3;
+
+// Define a trait for choosing a payload
+pub trait PayloadSelector {
+    fn select_payload(
+        &self,
+        local_payload: Result<OptimismExecutionPayloadEnvelopeV3, ClientError>,
+        builder_payloads: Vec<Result<OptimismExecutionPayloadEnvelopeV3, ClientError>>,
+    ) -> Result<OptimismExecutionPayloadEnvelopeV3, ClientError>;
+}
+
+pub struct DefaultPayloadSelector;
+
+impl PayloadSelector for DefaultPayloadSelector {
+    fn select_payload(
+        &self,
+        local_payload: Result<OptimismExecutionPayloadEnvelopeV3, ClientError>,
+        builder_payloads: Vec<Result<OptimismExecutionPayloadEnvelopeV3, ClientError>>,
+    ) -> Result<OptimismExecutionPayloadEnvelopeV3, ClientError> {
+        builder_payloads
+            .iter()
+            .filter_map(|payload| payload.as_ref().ok())
+            .max_by_key(|p| p.block_value)
+            .map(|p| Ok(p.clone()))
+            .unwrap_or(local_payload)
+    }
+}

src/server.rs

@@ -3,6 +3,7 @@ use alloy_rpc_types_engine::{
     ExecutionPayload, ExecutionPayloadV3, ForkchoiceState, ForkchoiceUpdated, PayloadId,
     PayloadStatus,
 };
+use futures::future::join_all;
 use jsonrpsee::core::{async_trait, ClientError, RpcResult};
 use jsonrpsee::http_client::transport::HttpBackend;
 use jsonrpsee::http_client::HttpClient;
@@ -16,6 +17,8 @@ use reth_rpc_layer::AuthClientService;
 use std::sync::Arc;
 use tracing::{error, info};
 
+use crate::selector::{DefaultPayloadSelector, PayloadSelector};
+
 #[rpc(server, client, namespace = "engine")]
 pub trait EngineApi {
     #[method(name = "forkchoiceUpdatedV3")]
@@ -42,20 +45,22 @@ pub trait EngineApi {
 
 pub struct EthEngineApi<S = AuthClientService<HttpBackend>> {
     l2_client: Arc<HttpClient<S>>,
-    builder_client: Arc<HttpClient<S>>,
+    builder_clients: Vec<Arc<HttpClient<S>>>,
+    payload_selector: Arc<dyn PayloadSelector + Send + Sync>,
     boost_sync: bool,
 }
 
 impl<S> EthEngineApi<S> {
     pub fn new(
         l2_client: Arc<HttpClient<S>>,
-        builder_client: Arc<HttpClient<S>>,
+        builder_clients: Vec<Arc<HttpClient<S>>>,
         boost_sync: bool,
     ) -> Self {
         Self {
             l2_client,
-            builder_client,
+            builder_clients,
             boost_sync,
+            payload_selector: Arc::new(DefaultPayloadSelector),
         }
     }
 }
@@ -85,11 +90,12 @@ impl EngineApiServer for EthEngineApi {
         };
 
         if should_send_to_builder {
-            // async call to builder to trigger payload building and sync
-            let builder = self.builder_client.clone();
-            let attr = payload_attributes.clone();
-            tokio::spawn(async move {
-                builder.fork_choice_updated_v3(fork_choice_state, attr).await.map(|response| {
+            // async call to each builder to trigger payload building and sync
+            for builder in self.builder_clients.iter() {
+                let builder = builder.clone();
+                let attr = payload_attributes.clone();
+                tokio::spawn(async move {
+                    builder.fork_choice_updated_v3(fork_choice_state, attr).await.map(|response| {
                     let payload_id_str = response.payload_id.map(|id| id.to_string()).unwrap_or_default();
                     if response.is_invalid() {
                         error!(message = "builder rejected fork_choice_updated_v3 with attributes", "payload_id" = payload_id_str, "validation_error" = %response.payload_status.status);
@@ -99,7 +105,8 @@ impl EngineApiServer for EthEngineApi {
                 }).map_err(|e| {
                     error!(message = "error calling fork_choice_updated_v3 to builder", "error" = %e, "head_block_hash" = %fork_choice_state.head_block_hash);
                 })
-            });
+                });
+            }
         } else {
             info!(message = "no payload attributes provided or no_tx_pool is set", "head_block_hash" = %fork_choice_state.head_block_hash);
         }
@@ -126,47 +133,53 @@ impl EngineApiServer for EthEngineApi {
     ) -> RpcResult<OptimismExecutionPayloadEnvelopeV3> {
         info!(message = "received get_payload_v3", "payload_id" = %payload_id);
         let l2_client_future = self.l2_client.get_payload_v3(payload_id);
-        let builder_client_future = Box::pin(async {
-            let payload = self.builder_client.get_payload_v3(payload_id).await.map_err(|e| {
-                error!(message = "error calling get_payload_v3 from builder", "error" = %e, "payload_id" = %payload_id);
-                e
-            })?;
-
-            info!(message = "received payload from builder", "payload_id" = %payload_id, "block_hash" = %payload.as_v1_payload().block_hash);
-
-            // Send the payload to the local execution engine with engine_newPayload to validate the block from the builder.
-            // Otherwise, we do not want to risk the network to a halt since op-node will not be able to propose the block.
-            // If validation fails, return the local block since that one has already been validated.
-            let payload_status = self.l2_client.new_payload_v3(payload.execution_payload.clone(), vec![], payload.parent_beacon_block_root).await.map_err(|e| {
-                error!(message = "error calling new_payload_v3 to validate builder payload", "error" = %e, "payload_id" = %payload_id);
-                e
-            })?;
-            if payload_status.is_invalid() {
+        let builder_client_futures = self.builder_clients.iter().map(|builder| {
+            let builder = builder.clone();
+            Box::pin(async move {
+                let payload = builder.get_payload_v3(payload_id).await.map_err(|e| {
+                    error!(message = "error calling get_payload_v3 from builder", "error" = %e, "payload_id" = %payload_id);
+                    e
+                })?;
+
+                info!(message = "received payload from builder", "payload_id" = %payload_id, "block_hash" = %payload.as_v1_payload().block_hash);
+
+                // Send the payload to the local execution engine with engine_newPayload to validate the block from the builder.
+                // Otherwise, we do not want to risk the network to a halt since op-node will not be able to propose the block.
+                // If validation fails, return the local block since that one has already been validated.
+                let payload_status = self.l2_client.new_payload_v3(payload.execution_payload.clone(), vec![], payload.parent_beacon_block_root).await.map_err(|e| {
+                    error!(message = "error calling new_payload_v3 to validate builder payload", "error" = %e, "payload_id" = %payload_id);
+                    e
+                })?;
+                if payload_status.is_invalid() {
                 error!(message = "builder payload was not valid", "payload_status" = %payload_status.status, "payload_id" = %payload_id);
                 Err(ClientError::Call(ErrorObject::owned(
                     INVALID_REQUEST_CODE,
                     "Builder payload was not valid",
                     None::<String>,
-                )))
-            } else {
-                info!(message = "received payload status from local execution engine validating builder payload", "payload_id" = %payload_id);
-                Ok(payload)
-            }
-        });
-
-        let (l2_payload, builder_payload) = tokio::join!(l2_client_future, builder_client_future);
-
-        builder_payload.or(l2_payload).map_err(|e| match e {
-            ClientError::Call(err) => err, // Already an ErrorObjectOwned, so just return it
-            other_error => {
-                error!(
-                    message = "error calling get_payload_v3",
-                    "error" = %other_error,
-                    "payload_id" = %payload_id
-                );
-                ErrorCode::InternalError.into()
-            }
-        })
+                    )))
+                    } else {
+                    info!(message = "received payload status from local execution engine validating builder payload", "payload_id" = %payload_id);
+                    Ok(payload)
+                }
+            })
+        }).collect::<Vec<_>>();
+
+        let (l2_payload, builder_payloads) =
+            tokio::join!(l2_client_future, join_all(builder_client_futures));
+
+        self.payload_selector
+            .select_payload(l2_payload, builder_payloads)
+            .map_err(|e| match e {
+                ClientError::Call(err) => err, // Already an ErrorObjectOwned, so just return it
+                other_error => {
+                    error!(
+                        message = "error calling get_payload_v3",
+                        "error" = %other_error,
+                        "payload_id" = %payload_id
+                    );
+                    ErrorCode::InternalError.into()
+                }
+            })
     }
 
     async fn new_payload_v3(
@@ -180,11 +193,12 @@ impl EngineApiServer for EthEngineApi {
 
         // async call to builder to sync the builder node
         if self.boost_sync {
-            let builder = self.builder_client.clone();
-            let builder_payload = payload.clone();
-            let builder_versioned_hashes = versioned_hashes.clone();
-            tokio::spawn(async move {
-                builder.new_payload_v3(builder_payload, builder_versioned_hashes, parent_beacon_block_root).await
+            for builder in self.builder_clients.iter() {
+                let builder = builder.clone();
+                let builder_payload = payload.clone();
+                let builder_versioned_hashes = versioned_hashes.clone();
+                tokio::spawn(async move {
+                    builder.new_payload_v3(builder_payload, builder_versioned_hashes, parent_beacon_block_root).await
                 .map(|response: PayloadStatus| {
                     if response.is_invalid() {
                         error!(message = "builder rejected new_payload_v3", "block_hash" = %block_hash);
@@ -195,7 +209,8 @@ impl EngineApiServer for EthEngineApi {
                     error!(message = "error calling new_payload_v3 to builder", "error" = %e, "block_hash" = %block_hash);
                     e
                 })
-            });
+                });
+            }
         }
 
         self.l2_client