chore: add sleep log in `fetch_logs_with_cursor` (#4734)

### Description

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### Drive-by changes

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### Related issues

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- Fixes #[issue number here]
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### Backward compatibility

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rust/main/config/mainnet_config.json

@@ -784,7 +784,8 @@
       "gasCurrencyCoinGeckoId": "ethereum",
       "index": {
         "from": 1,
-        "mode": "sequence"
+        "mode": "sequence",
+        "chunk": 100
       },
       "interchainGasPaymaster": "ABb3i11z7wKoGCfeRQNQbVYWjAm7jG7HzZnDLV4RKRbK",
       "mailbox": "EitxJuv2iBjsg2d7jVy2LDC1e2zBrx4GB5Y9h2Ko3A9Y",
@@ -2804,7 +2805,8 @@
       "gasCurrencyCoinGeckoId": "solana",
       "index": {
         "from": 1,
-        "mode": "sequence"
+        "mode": "sequence",
+        "chunk": 100
       },
       "interchainGasPaymaster": "JAvHW21tYXE9dtdG83DReqU2b4LUexFuCbtJT5tF8X6M",
       "mailbox": "E588QtVUvresuXq2KoNEwAmoifCzYGpRBdHByN9KQMbi",

rust/main/hyperlane-base/src/contract_sync/mod.rs

@@ -170,7 +170,7 @@ where
                     Ok(logs) => logs,
                     Err(err) => {
                         warn!(?err, ?range, "Error fetching logs in range");
-                        break SLEEP_DURATION;
+                        break Some(SLEEP_DURATION);
                     }
                 };
 
@@ -196,13 +196,20 @@ where
                 // Update cursor
                 if let Err(err) = cursor.update(logs, range).await {
                     warn!(?err, "Error updating cursor");
-                    break SLEEP_DURATION;
+                    break Some(SLEEP_DURATION);
                 };
-                break Default::default();
+                break None;
             },
-            CursorAction::Sleep(duration) => duration,
+            CursorAction::Sleep(duration) => Some(duration),
         };
-        sleep(sleep_duration).await
+        if let Some(sleep_duration) = sleep_duration {
+            debug!(
+                cursor = ?cursor,
+                ?sleep_duration,
+                "Cursor can't make progress, sleeping",
+            );
+            sleep(sleep_duration).await
+        }
     }
 
     async fn dedupe_and_store_logs(

rust/main/hyperlane-base/src/settings/parser/mod.rs

@@ -34,6 +34,8 @@ pub use self::json_value_parser::ValueParser;
 mod connection_parser;
 mod json_value_parser;
 
+const DEFAULT_CHUNK_SIZE: u32 = 1999;
+
 /// The base agent config
 #[derive(Debug, Deserialize)]
 #[serde(transparent)]
@@ -152,7 +154,7 @@ fn parse_chain(
         .get_opt_key("index")
         .get_opt_key("chunk")
         .parse_u32()
-        .unwrap_or(1999);
+        .unwrap_or(DEFAULT_CHUNK_SIZE);
     let mode = chain
         .chain(&mut err)
         .get_opt_key("index")