fix(flashbots): Do not block on submission (#184)

There's no point of blocking when we send the bundle to flashbots. The only thing we do after is record metrics. This will matter more on a production environment where network lag could occur on services we don't control (flashbots). I think blocking on quincey/getting the nonce on `prepare` is OK.

Author: Evalir

src/tasks/submit/flashbots.rs

@@ -14,7 +14,7 @@ use alloy::{
 use eyre::OptionExt;
 use init4_bin_base::{deps::metrics::counter, utils::signer::LocalOrAws};
 use tokio::{sync::mpsc, task::JoinHandle};
-use tracing::{Instrument, debug, debug_span};
+use tracing::{Instrument, debug, debug_span, error};
 
 /// Handles preparation and submission of simulated rollup blocks to the
 /// Flashbots relay as MEV bundles.
@@ -188,28 +188,33 @@ impl FlashbotsTask {
 
             // Send the bundle to Flashbots, instrumenting the send future so all
             // events inside the async send are attributed to the submit span.
-            let response = self
-                .flashbots()
-                .send_mev_bundle(bundle.clone())
-                .with_auth(self.signer.clone())
-                .into_future()
-                .instrument(submit_span.clone())
-                .await;
-
-            match response {
-                Ok(resp) => {
-                    counter!("signet.builder.flashbots.bundles_submitted").increment(1);
-                    span_debug!(
-                        submit_span,
-                        hash = resp.map(|r| r.bundle_hash.to_string()),
-                        "received bundle hash after submitted to flashbots"
-                    );
+            let flashbots = self.flashbots().to_owned();
+            let signer = self.signer.clone();
+
+            tokio::spawn(
+                async move {
+                    let response = flashbots
+                        .send_mev_bundle(bundle.clone())
+                        .with_auth(signer.clone())
+                        .into_future()
+                        .await;
+
+                    match response {
+                        Ok(resp) => {
+                            counter!("signet.builder.flashbots.bundles_submitted").increment(1);
+                            debug!(
+                                hash = resp.map(|r| r.bundle_hash.to_string()),
+                                "received bundle hash after submitted to flashbots"
+                            );
+                        }
+                        Err(err) => {
+                            counter!("signet.builder.flashbots.submission_failures").increment(1);
+                            error!(%err, "MEV bundle submission failed - error returned");
+                        }
+                    }
                 }
-                Err(err) => {
-                    counter!("signet.builder.flashbots.submission_failures").increment(1);
-                    span_error!(submit_span, %err, "MEV bundle submission failed - error returned");
-                }
-            }
+                .instrument(submit_span.clone()),
+            );
         }
     }