Problem: check_for_events overflow when the current block is lower th…

…an blockdelay (#180)

orchestrator/orchestrator/src/ethereum_event_watcher.rs

@@ -42,7 +42,7 @@ pub async fn check_for_events<S: Signer + 'static, CS: CosmosSigner>(
     let prefix = contact.get_prefix();
     let our_cosmos_address = cosmos_key.to_address(&prefix).unwrap();
     let latest_block = get_block_number_with_retry(eth_client.clone()).await;
-    let latest_block = latest_block - block_delay;
+    let latest_block = latest_block.saturating_sub(block_delay);
 
     let mut ending_block = starting_block + blocks_to_search;
     if ending_block > latest_block {
@@ -72,6 +72,8 @@ pub async fn check_for_events<S: Signer + 'static, CS: CosmosSigner>(
 
     let search_range = starting_block..ending_block;
 
+    info!("check_for_events from {:?} to {:?}", starting_block, ending_block);
+
     // select uses an inclusive version of the range
     erc20_deployed_filter = erc20_deployed_filter.select(search_range.clone());
     logic_call_filter = logic_call_filter.select(search_range.clone());