Add get_next_last_id

src/thin_client.rs

@@ -262,6 +262,19 @@ impl ThinClient {
         }
     }
 
+    /// Request a new last Entry ID from the server. This method blocks
+    /// until the server sends a response.
+    pub fn get_next_last_id(&mut self, previous_last_id: &Hash) -> Hash {
+        loop {
+            let last_id = self.get_last_id();
+            if last_id != *previous_last_id {
+                break last_id;
+            }
+            debug!("Got same last_id ({:?}), will retry...", last_id);
+            sleep(Duration::from_millis(100));
+        }
+    }
+
     pub fn submit_poll_balance_metrics(elapsed: &Duration) {
         solana_metrics::submit(
             influxdb::Point::new("thinclient")