[indexer-alt] Add ingested_checkpoint_timestamp_lag_ms metric

crates/sui-indexer-alt/src/ingestion/broadcaster.rs

@@ -80,6 +80,10 @@ pub(super) fn broadcaster(
                     let old_seq = latest_ingested_checkpoint.fetch_max(new_seq, Ordering::Relaxed);
                     if new_seq > old_seq {
                         metrics.latest_ingested_checkpoint.set(new_seq as i64);
+                        metrics.ingested_checkpoint_timestamp_lag_ms.set(
+                            chrono::Utc::now().timestamp_millis()
+                                - checkpoint.checkpoint_summary.timestamp_ms as i64,
+                        );
                     }
                     let futures = subscribers.iter().map(|s| s.send(checkpoint.clone()));
 

crates/sui-indexer-alt/src/metrics.rs

@@ -62,6 +62,7 @@ pub struct IndexerMetrics {
     pub total_ingested_not_found_retries: IntCounter,
 
     pub latest_ingested_checkpoint: IntGauge,
+    pub ingested_checkpoint_timestamp_lag_ms: IntGauge,
 
     pub ingested_checkpoint_latency: Histogram,
 
@@ -208,6 +209,13 @@ impl IndexerMetrics {
                 registry,
             )
             .unwrap(),
+            ingested_checkpoint_timestamp_lag_ms: register_int_gauge_with_registry!(
+                "ingested_checkpoint_timestamp_lag_ms",
+                "Difference between the system timestamp when the latest checkpoint was fetched and the \
+                 timestamp in the checkpoint, in milliseconds",
+                registry,
+            )
+            .unwrap(),
             ingested_checkpoint_latency: register_histogram_with_registry!(
                 "indexer_ingested_checkpoint_latency",
                 "Time taken to fetch a checkpoint from the remote store, including retries",