fallback to v1 api on 404 relay response

crates/common/src/pbs/error.rs

@@ -47,6 +47,10 @@ impl PbsError {
             _ => false,
         }
     }
+
+    pub fn is_not_found(&self) -> bool {
+        matches!(&self, PbsError::RelayResponse { code: 404, .. })
+    }
 }
 
 #[derive(Debug, Error, PartialEq, Eq)]

crates/pbs/src/mev_boost/submit_block.rs

@@ -88,7 +88,7 @@ async fn submit_block_with_timeout(
     api_version: &BuilderApiVersion,
     fork_name: ForkName,
 ) -> Result<Option<SubmitBlindedBlockResponse>, PbsError> {
-    let url = relay.submit_block_url(*api_version)?;
+    let mut url = relay.submit_block_url(*api_version)?;
     let mut remaining_timeout_ms = timeout_ms;
     let mut retry = 0;
     let mut backoff = Duration::from_millis(250);
@@ -121,6 +121,14 @@ async fn submit_block_with_timeout(
                 }
             }
 
+            Err(err) if err.is_not_found() && matches!(api_version, BuilderApiVersion::V2) => {
+                warn!(
+                    relay_id = relay.id.as_ref(),
+                    "relay does not support v2 endpoint, retrying with v1"
+                );
+                url = relay.submit_block_url(BuilderApiVersion::V1)?;
+            }
+
             Err(err) => return Err(err),
         };
 
@@ -184,8 +192,16 @@ async fn send_submit_block(
         warn!(relay_id = relay.id.as_ref(), retry, %err, "failed to get payload (this might be ok if other relays have it)");
         return Err(err);
     };
+
     if api_version != &BuilderApiVersion::V1 {
         // v2 response is going to be empty, so just break here
+        debug!(
+            relay_id = relay.id.as_ref(),
+            retry,
+            latency = ?request_latency,
+            "successful request"
+        );
+
         return Ok(None);
     }