add error case for layout not ready, and fail earlier in many places

src/rpc/layout/manager.rs

@@ -105,7 +105,7 @@ impl LayoutManager {
 	}
 
 	pub fn add_table(&self, table_name: &'static str) {
-		let first_version = self.layout().versions().first().unwrap().version;
+		let first_version = self.layout().inner().versions.first().unwrap().version;
 
 		self.table_sync_version
 			.lock()
@@ -139,19 +139,20 @@ impl LayoutManager {
 
 	// ---- ACK LOCKING ----
 
-	pub fn write_lock_with<T, F>(self: &Arc<Self>, f: F) -> WriteLock<T>
+	pub fn write_lock_with<T, F>(self: &Arc<Self>, f: F) -> Result<WriteLock<T>, Error>
 	where
-		F: FnOnce(&LayoutHelper) -> T,
+		F: FnOnce(&[LayoutVersion]) -> T,
 	{
 		let layout = self.layout();
-		let version = layout.current().version;
-		let value = f(&layout);
+		let current_version = layout.current()?.version;
+		let versions = layout.versions()?;
+		let value = f(versions);
 		layout
 			.ack_lock
-			.get(&version)
+			.get(&current_version)
 			.unwrap()
 			.fetch_add(1, Ordering::Relaxed);
-		WriteLock::new(version, self, value)
+		Ok(WriteLock::new(current_version, self, value))
 	}
 
 	// ---- INTERNALS ---
@@ -369,7 +370,7 @@ impl<T> Drop for WriteLock<T> {
 		let layout = self.layout_manager.layout(); // acquire read lock
 		if let Some(counter) = layout.ack_lock.get(&self.layout_version) {
 			let prev_lock = counter.fetch_sub(1, Ordering::Relaxed);
-			if prev_lock == 1 && layout.current().version > self.layout_version {
+			if prev_lock == 1 && layout.current().unwrap().version > self.layout_version {
 				drop(layout); // release read lock, write lock will be acquired
 				self.layout_manager.ack_new_version();
 			}