From 3ef78520da19bf96ef4b3adb2759004b63ea075d Mon Sep 17 00:00:00 2001
From: gamandeepsingh <gamandeepsingh4@gmail.com>
Date: Sat, 25 Jul 2026 02:47:55 +0530
Subject: [PATCH] fix: dragonsmouth-from-slot '*' falls back to gRPC slot on
 empty blocks_metadata

resolve_initial_from_slot hard-errored when blocks_metadata had zero
rows, contradicting the documented fallback behavior. Empty table now
resolves to (None, FromSlotMode::LatestDb) so the initial subscribe
request omits from_slot and gRPC starts from its own reported slot,
the same outcome already used when a resolved slot turns out stale.

Fixes #56
---
 crates/superbank/README.md          |  4 +++-
 crates/superbank/src/ingest/grpc.rs | 30 ++++++++++++++++-------------
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/crates/superbank/README.md b/crates/superbank/README.md
index eef13f9..2389877 100644
--- a/crates/superbank/README.md
+++ b/crates/superbank/README.md
@@ -227,7 +227,9 @@ cargo run -p superbank -- --config path/to/superbank.yaml
 - `dragonsmouth-from-slot: 0` attempts slot 0; if unavailable, superbank parses the gRPC error to
   find the earliest available slot.
 - `dragonsmouth-from-slot: "*"` uses the highest slot in `blocks_metadata` before subscribing; if
-  rejected, superbank falls back to the gRPC-reported available slot.
+  rejected, superbank falls back to the gRPC-reported available slot. If `blocks_metadata` has no
+  rows yet (fresh deployment), superbank skips straight to that same gRPC-reported available slot
+  instead of erroring.
 - For seeded live-tail gRPC deployments, prefer `dragonsmouth-from-slot: "*"` so process restarts
   resume from the latest durable ClickHouse slot instead of replaying from the earliest available
   upstream slot.
diff --git a/crates/superbank/src/ingest/grpc.rs b/crates/superbank/src/ingest/grpc.rs
index 33d455f..fd53498 100644
--- a/crates/superbank/src/ingest/grpc.rs
+++ b/crates/superbank/src/ingest/grpc.rs
@@ -483,20 +483,24 @@ async fn resolve_initial_from_slot(
 ) -> Result<(Option<u64>, Option<FromSlotMode>)> {
     match args.dragonsmouth_from_slot {
         Some(FromSlotSpec::LatestDb) => {
-            let latest = fetch_latest_slot_from_blocks(clickhouse, &args.blocks_table)
-                .await?
-                .ok_or_else(|| {
-                    anyhow!(
-                        "dragonsmouth-from-slot '*' requires at least one row in {}",
+            match fetch_latest_slot_from_blocks(clickhouse, &args.blocks_table).await? {
+                Some(latest) => {
+                    info!(
+                        slot = latest,
+                        table = %args.blocks_table,
+                        "resolved dragonsmouth-from-slot='*' to latest slot in blocks_metadata"
+                    );
+                    Ok((Some(latest), Some(FromSlotMode::LatestDb)))
+                }
+                None => {
+                    info!(
+                        table = %args.blocks_table,
+                        "dragonsmouth-from-slot='*' found no rows in {}; falling back to gRPC-reported available slot",
                         args.blocks_table
-                    )
-                })?;
-            info!(
-                slot = latest,
-                table = %args.blocks_table,
-                "resolved dragonsmouth-from-slot='*' to latest slot in blocks_metadata"
-            );
-            Ok((Some(latest), Some(FromSlotMode::LatestDb)))
+                    );
+                    Ok((None, Some(FromSlotMode::LatestDb)))
+                }
+            }
         }
         Some(FromSlotSpec::Slot(0)) => Ok((Some(0), Some(FromSlotMode::Zero))),
         Some(FromSlotSpec::Slot(slot)) => Ok((Some(slot), Some(FromSlotMode::Strict))),