Added simple x-timeout-ms header support to get_header

Author: jclapis

crates/common/src/pbs/constants.rs

@@ -16,6 +16,7 @@ pub const RELOAD_PATH: &str = "/reload";
 pub const HEADER_VERSION_KEY: &str = "X-CommitBoost-Version";
 pub const HEADER_VERSION_VALUE: &str = COMMIT_BOOST_VERSION;
 pub const HEADER_START_TIME_UNIX_MS: &str = "Date-Milliseconds";
+pub const HEADER_TIMEOUT_MS: &str = "X-Timeout-Ms";
 
 pub const BUILDER_EVENTS_PATH: &str = "/builder_events";
 pub const DEFAULT_PBS_JWT_KEY: &str = "DEFAULT_PBS";

crates/pbs/src/mev_boost/get_header.rs

@@ -14,7 +14,7 @@ use cb_common::{
     pbs::{
         error::{PbsError, ValidationError},
         GetHeaderParams, GetHeaderResponse, RelayClient, VersionedResponse, EMPTY_TX_ROOT_HASH,
-        HEADER_START_TIME_UNIX_MS,
+        HEADER_START_TIME_UNIX_MS, HEADER_TIMEOUT_MS,
     },
     signature::verify_signed_message,
     types::{BlsPublicKey, BlsSignature, Chain},
@@ -81,6 +81,31 @@ pub async fn get_header<S: BuilderApiState>(
         return Ok(None);
     }
 
+    // Use the minimum of the time left and the user provided timeout header
+    let max_timeout_ms = match req_headers.get(HEADER_TIMEOUT_MS) {
+        Some(user_header_value) => match user_header_value.to_str() {
+            Ok(user_timeout_string) => match user_timeout_string.parse::<u64>() {
+                Ok(user_timeout) => {
+                    if user_timeout == 0 {
+                        warn!("user-supplied timeout header is 0, using {max_timeout_ms}ms");
+                        max_timeout_ms
+                    } else {
+                        user_timeout.min(max_timeout_ms)
+                    }
+                }
+                Err(e) => {
+                    warn!("cannot parse user-supplied timeout header '{user_timeout_string}', using {max_timeout_ms}ms ({e})");
+                    max_timeout_ms
+                }
+            },
+            Err(e) => {
+                warn!("invalid user-supplied timeout header, using {max_timeout_ms}ms ({e})");
+                max_timeout_ms
+            }
+        },
+        None => max_timeout_ms,
+    };
+
     // prepare headers, except for start time which is set in `send_one_get_header`
     let mut send_headers = HeaderMap::new();
     send_headers.insert(USER_AGENT, get_user_agent_with_version(&req_headers)?);
@@ -301,6 +326,10 @@ async fn send_one_get_header(
     let start_request_time = utcnow_ms();
     req_config.headers.insert(HEADER_START_TIME_UNIX_MS, HeaderValue::from(start_request_time));
 
+    // The timeout header indicating how long a relay has to respond, so they can
+    // minimize timing games without losing the bid
+    req_config.headers.insert(HEADER_TIMEOUT_MS, HeaderValue::from(req_config.timeout_ms));
+
     let start_request = Instant::now();
     let res = match relay
         .client