feat: Add logging to agents (#5167)

### Description

Add logging to agents
* When an agent start
* When cursor indexing task is exiting
* When cursor sync method is exiting

### Related issues

- Contributes into
#5098

### Backward compatibility

Yes

### Testing

E2E tests

---------

Co-authored-by: Danil Nemirovsky <[email protected]>

rust/main/agents/relayer/src/main.rs

@@ -18,6 +18,9 @@ mod memory_profiler;
 
 #[tokio::main(flavor = "multi_thread", worker_threads = 20)]
 async fn main() -> Result<()> {
+    // Logging is not initialised at this point, so, using `println!`
+    println!("Relayer starting up...");
+
     let agent_main_fut = agent_main::<Relayer>();
 
     #[cfg(feature = "memory-profiling")]

rust/main/agents/relayer/src/relayer.rs

@@ -465,11 +465,11 @@ impl Relayer {
                 return tokio::spawn(async {}).instrument(info_span!("MessageSync"));
             }
         };
+        let origin_name = origin.name().to_string();
         tokio::spawn(TaskMonitor::instrument(&task_monitor, async move {
-            contract_sync
-                .clone()
-                .sync("dispatched_messages", cursor.into())
-                .await
+            let label = "dispatched_messages";
+            contract_sync.clone().sync(label, cursor.into()).await;
+            info!(chain = origin_name, label, "contract sync task exit");
         }))
         .instrument(info_span!("MessageSync"))
     }
@@ -496,14 +496,14 @@ impl Relayer {
                 return tokio::spawn(async {}).instrument(info_span!("IgpSync"));
             }
         };
+        let origin_name = origin.name().to_string();
         tokio::spawn(TaskMonitor::instrument(&task_monitor, async move {
+            let label = "gas_payments";
             contract_sync
                 .clone()
-                .sync(
-                    "gas_payments",
-                    SyncOptions::new(Some(cursor), tx_id_receiver),
-                )
-                .await
+                .sync(label, SyncOptions::new(Some(cursor), tx_id_receiver))
+                .await;
+            info!(chain = origin_name, label, "contract sync task exit");
         }))
         .instrument(info_span!("IgpSync"))
     }
@@ -526,14 +526,14 @@ impl Relayer {
                 return tokio::spawn(async {}).instrument(info_span!("MerkleTreeHookSync"));
             }
         };
+        let origin_name = origin.name().to_string();
         tokio::spawn(TaskMonitor::instrument(&task_monitor, async move {
+            let label = "merkle_tree_hook";
             contract_sync
                 .clone()
-                .sync(
-                    "merkle_tree_hook",
-                    SyncOptions::new(Some(cursor), tx_id_receiver),
-                )
-                .await
+                .sync(label, SyncOptions::new(Some(cursor), tx_id_receiver))
+                .await;
+            info!(chain = origin_name, label, "contract sync task exit");
         }))
         .instrument(info_span!("MerkleTreeHookSync"))
     }

rust/main/agents/scraper/src/main.rs

@@ -26,5 +26,8 @@ mod store;
 
 #[tokio::main(flavor = "current_thread")]
 async fn main() -> Result<()> {
+    // Logging is not initialised at this point, so, using `println!`
+    println!("Scraper agent starting up...");
+
     agent_main::<Scraper>().await
 }

rust/main/agents/validator/src/main.rs

@@ -16,5 +16,8 @@ mod validator;
 
 #[tokio::main(flavor = "current_thread")]
 async fn main() -> Result<()> {
+    // Logging is not initialised at this point, so, using `println!`
+    println!("Validator starting up...");
+
     agent_main::<Validator>().await
 }

rust/main/agents/validator/src/validator.rs

@@ -228,11 +228,11 @@ impl Validator {
                     self.origin_chain
                 )
             });
+        let origin = self.origin_chain.name().to_string();
         tokio::spawn(async move {
-            contract_sync
-                .clone()
-                .sync("merkle_tree_hook", cursor.into())
-                .await;
+            let label = "merkle_tree_hook";
+            contract_sync.clone().sync(label, cursor.into()).await;
+            info!(chain = origin, label, "contract sync task exit");
         })
         .instrument(info_span!("MerkleTreeHookSyncer"))
     }

rust/main/hyperlane-base/src/agent.rs

@@ -80,6 +80,9 @@ pub async fn agent_main<A: BaseAgent>() -> Result<()> {
     // the variable defaults to "VERGEN_IDEMPOTENT_OUTPUT".
     let git_sha = env!("VERGEN_GIT_SHA").to_owned();
 
+    // Logging is not initialised at this point, so, using `println!`
+    println!("Agent {} starting up with version {git_sha}", A::AGENT_NAME);
+
     let agent_metadata = AgentMetadata::new(git_sha);
 
     let settings = A::Settings::load()?;

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

@@ -107,7 +107,17 @@ where
                 self.fetch_logs_with_cursor(cursor, &stored_logs_metric, &indexed_height_metric)
                     .await;
             }
+
+            // Added so that we confuse compiler that it is an infinite loop
+            if false {
+                break;
+            }
         }
+
+        // Although the above loop should never end (unless by panicking),
+        // we put log here to make sure that we see when this method returns normally.
+        // Hopefully, compiler will not optimise this code out.
+        info!(chain = chain_name, label, "contract sync loop exit");
     }
 
     #[instrument(fields(domain=self.domain().name()), skip(self, recv, stored_logs_metric))]