pageserver: add disk consistent and remote lsn metrics (#10005)

## Problem

There's no metrics for disk consistent LSN and remote LSN. This stuff is
useful when looking at ingest performance.

## Summary of changes

Two per timeline metrics are added: `pageserver_disk_consistent_lsn` and
`pageserver_projected_remote_consistent_lsn`. I went for the projected
remote lsn instead of the visible one
because that more closely matches remote storage write tput. Ideally we
would have both, but these metrics are expensive.

pageserver/src/metrics.rs

@@ -464,6 +464,24 @@ static LAST_RECORD_LSN: Lazy<IntGaugeVec> = Lazy::new(|| {
     .expect("failed to define a metric")
 });
 
+static DISK_CONSISTENT_LSN: Lazy<IntGaugeVec> = Lazy::new(|| {
+    register_int_gauge_vec!(
+        "pageserver_disk_consistent_lsn",
+        "Disk consistent LSN grouped by timeline",
+        &["tenant_id", "shard_id", "timeline_id"]
+    )
+    .expect("failed to define a metric")
+});
+
+pub(crate) static PROJECTED_REMOTE_CONSISTENT_LSN: Lazy<UIntGaugeVec> = Lazy::new(|| {
+    register_uint_gauge_vec!(
+        "pageserver_projected_remote_consistent_lsn",
+        "Projected remote consistent LSN grouped by timeline",
+        &["tenant_id", "shard_id", "timeline_id"]
+    )
+    .expect("failed to define a metric")
+});
+
 static PITR_HISTORY_SIZE: Lazy<UIntGaugeVec> = Lazy::new(|| {
     register_uint_gauge_vec!(
         "pageserver_pitr_history_size",
@@ -2394,7 +2412,8 @@ pub(crate) struct TimelineMetrics {
     pub load_layer_map_histo: StorageTimeMetrics,
     pub garbage_collect_histo: StorageTimeMetrics,
     pub find_gc_cutoffs_histo: StorageTimeMetrics,
-    pub last_record_gauge: IntGauge,
+    pub last_record_lsn_gauge: IntGauge,
+    pub disk_consistent_lsn_gauge: IntGauge,
     pub pitr_history_size: UIntGauge,
     pub archival_size: UIntGauge,
     pub(crate) layer_size_image: UIntGauge,
@@ -2475,7 +2494,11 @@ impl TimelineMetrics {
             &shard_id,
             &timeline_id,
         );
-        let last_record_gauge = LAST_RECORD_LSN
+        let last_record_lsn_gauge = LAST_RECORD_LSN
+            .get_metric_with_label_values(&[&tenant_id, &shard_id, &timeline_id])
+            .unwrap();
+
+        let disk_consistent_lsn_gauge = DISK_CONSISTENT_LSN
             .get_metric_with_label_values(&[&tenant_id, &shard_id, &timeline_id])
             .unwrap();
 
@@ -2578,7 +2601,8 @@ impl TimelineMetrics {
             garbage_collect_histo,
             find_gc_cutoffs_histo,
             load_layer_map_histo,
-            last_record_gauge,
+            last_record_lsn_gauge,
+            disk_consistent_lsn_gauge,
             pitr_history_size,
             archival_size,
             layer_size_image,
@@ -2642,6 +2666,7 @@ impl TimelineMetrics {
         let timeline_id = &self.timeline_id;
         let shard_id = &self.shard_id;
         let _ = LAST_RECORD_LSN.remove_label_values(&[tenant_id, shard_id, timeline_id]);
+        let _ = DISK_CONSISTENT_LSN.remove_label_values(&[tenant_id, shard_id, timeline_id]);
         let _ = FLUSH_WAIT_UPLOAD_TIME.remove_label_values(&[tenant_id, shard_id, timeline_id]);
         let _ = STANDBY_HORIZON.remove_label_values(&[tenant_id, shard_id, timeline_id]);
         {
@@ -2805,6 +2830,7 @@ pub(crate) struct RemoteTimelineClientMetrics {
     calls: Mutex<HashMap<(&'static str, &'static str), IntCounterPair>>,
     bytes_started_counter: Mutex<HashMap<(&'static str, &'static str), IntCounter>>,
     bytes_finished_counter: Mutex<HashMap<(&'static str, &'static str), IntCounter>>,
+    pub(crate) projected_remote_consistent_lsn_gauge: UIntGauge,
 }
 
 impl RemoteTimelineClientMetrics {
@@ -2819,6 +2845,10 @@ impl RemoteTimelineClientMetrics {
                 .unwrap(),
         );
 
+        let projected_remote_consistent_lsn_gauge = PROJECTED_REMOTE_CONSISTENT_LSN
+            .get_metric_with_label_values(&[&tenant_id_str, &shard_id_str, &timeline_id_str])
+            .unwrap();
+
         RemoteTimelineClientMetrics {
             tenant_id: tenant_id_str,
             shard_id: shard_id_str,
@@ -2827,6 +2857,7 @@ impl RemoteTimelineClientMetrics {
             bytes_started_counter: Mutex::new(HashMap::default()),
             bytes_finished_counter: Mutex::new(HashMap::default()),
             remote_physical_size_gauge,
+            projected_remote_consistent_lsn_gauge,
         }
     }
 
@@ -3040,6 +3071,7 @@ impl Drop for RemoteTimelineClientMetrics {
             calls,
             bytes_started_counter,
             bytes_finished_counter,
+            projected_remote_consistent_lsn_gauge,
         } = self;
         for ((a, b), _) in calls.get_mut().unwrap().drain() {
             let mut res = [Ok(()), Ok(())];
@@ -3069,6 +3101,14 @@ impl Drop for RemoteTimelineClientMetrics {
             let _ = remote_physical_size_gauge; // use to avoid 'unused' warning in desctructuring above
             let _ = REMOTE_PHYSICAL_SIZE.remove_label_values(&[tenant_id, shard_id, timeline_id]);
         }
+        {
+            let _ = projected_remote_consistent_lsn_gauge;
+            let _ = PROJECTED_REMOTE_CONSISTENT_LSN.remove_label_values(&[
+                tenant_id,
+                shard_id,
+                timeline_id,
+            ]);
+        }
     }
 }
 

pageserver/src/tenant/remote_timeline_client.rs

@@ -2192,6 +2192,9 @@ impl RemoteTimelineClient {
                     upload_queue.clean.1 = Some(task.task_id);
 
                     let lsn = upload_queue.clean.0.metadata.disk_consistent_lsn();
+                    self.metrics
+                        .projected_remote_consistent_lsn_gauge
+                        .set(lsn.0);
 
                     if self.generation.is_none() {
                         // Legacy mode: skip validating generation

pageserver/src/tenant/timeline.rs

@@ -2392,7 +2392,7 @@ impl Timeline {
 
             result
                 .metrics
-                .last_record_gauge
+                .last_record_lsn_gauge
                 .set(disk_consistent_lsn.0 as i64);
             result
         })
@@ -3514,7 +3514,7 @@ impl Timeline {
     pub(crate) fn finish_write(&self, new_lsn: Lsn) {
         assert!(new_lsn.is_aligned());
 
-        self.metrics.last_record_gauge.set(new_lsn.0 as i64);
+        self.metrics.last_record_lsn_gauge.set(new_lsn.0 as i64);
         self.last_record_lsn.advance(new_lsn);
     }
 
@@ -3882,6 +3882,10 @@ impl Timeline {
     fn set_disk_consistent_lsn(&self, new_value: Lsn) -> bool {
         let old_value = self.disk_consistent_lsn.fetch_max(new_value);
         assert!(new_value >= old_value, "disk_consistent_lsn must be growing monotonously at runtime; current {old_value}, offered {new_value}");
+
+        self.metrics
+            .disk_consistent_lsn_gauge
+            .set(new_value.0 as i64);
         new_value != old_value
     }
 

test_runner/fixtures/metrics.py

@@ -152,6 +152,8 @@ PAGESERVER_PER_TENANT_METRICS: tuple[str, ...] = (
     "pageserver_resident_physical_size",
     "pageserver_io_operations_bytes_total",
     "pageserver_last_record_lsn",
+    "pageserver_disk_consistent_lsn",
+    "pageserver_projected_remote_consistent_lsn",
     "pageserver_standby_horizon",
     "pageserver_smgr_query_seconds_bucket",
     "pageserver_smgr_query_seconds_count",