metrics: add indexer_tip metrics

Signed-off-by: Eval EXEC <[email protected]>

Author: eval-exec

util/indexer/Cargo.toml

@@ -18,6 +18,7 @@ ckb-notify.workspace = true
 ckb-async-runtime.workspace = true
 ckb-indexer-sync.workspace = true
 rocksdb = { workspace = true, features = ["snappy"], default-features = false }
+ckb-metrics.workspace = true
 memchr.workspace = true
 
 [dev-dependencies]

util/indexer/src/indexer.rs

@@ -517,6 +517,12 @@ where
         if block_number % self.prune_interval == 0 {
             self.prune()?;
         }
+
+        // Update indexer tip metric
+        if let Some(metrics) = ckb_metrics::handle() {
+            metrics.ckb_indexer_tip.set(block_number as i64);
+        }
+
         Ok(())
     }
 
@@ -672,6 +678,16 @@ where
             batch.delete(Key::Header(block_number, &block_hash, filtered).into_vec())?;
 
             batch.commit()?;
+
+            // Update indexer tip metric after rollback
+            if let Some(metrics) = ckb_metrics::handle() {
+                // After rollback, the new tip is block_number - 1
+                if block_number > 0 {
+                    metrics.ckb_indexer_tip.set((block_number - 1) as i64);
+                } else {
+                    metrics.ckb_indexer_tip.set(0);
+                }
+            }
         }
         Ok(())
     }

util/metrics/src/lib.rs

@@ -130,6 +130,8 @@ pub struct Metrics {
     pub ckb_hole_punching_active_success_count: IntCounter,
     pub ckb_hole_punching_passive_count: IntCounter,
     pub ckb_hole_punching_passive_success_count: IntCounter,
+    /// Gauge metric for CKB indexer tip block number
+    pub ckb_indexer_tip: IntGauge,
 }
 
 static METRICS: std::sync::LazyLock<Metrics> = std::sync::LazyLock::new(|| {
@@ -336,6 +338,11 @@ static METRICS: std::sync::LazyLock<Metrics> = std::sync::LazyLock::new(|| {
         "The CKB hole punching passive success count"
     )
             .unwrap(),
+    ckb_indexer_tip: register_int_gauge!(
+        "ckb_indexer_tip",
+        "The CKB indexer tip block number"
+    )
+            .unwrap(),
     }
 });