fix: move metric updates to finish_compact_l0

pageserver/src/tenant/timeline.rs

@@ -3416,10 +3416,6 @@ impl Timeline {
             } else if LayerMap::is_l0(l.layer_desc()) {
                 return Err(CompactionError::Other(anyhow!("compaction generates a L0 layer file as output, which will cause infinite compaction.")));
             } else {
-                // update the timeline's physical size
-                self.metrics
-                    .resident_physical_size_gauge
-                    .add(l.layer_desc().file_size);
                 insert_layers.push(l);
             }
         }
@@ -3433,7 +3429,12 @@ impl Timeline {
 
         // deletion will happen later, the layer file manager sets wanted_garbage_collected
 
-        guard.finish_compact_l0(&layer_removal_cs, remove_layers, &insert_layers)?;
+        guard.finish_compact_l0(
+            &layer_removal_cs,
+            remove_layers,
+            &insert_layers,
+            &self.metrics,
+        )?;
 
         drop_wlock(guard);
 

pageserver/src/tenant/timeline/layer_manager.rs

@@ -206,6 +206,7 @@ impl LayerManager {
         layer_removal_cs: &Arc<tokio::sync::OwnedMutexGuard<()>>,
         compact_from: Vec<Arc<LayerE>>,
         compact_to: &[ResidentLayer],
+        metrics: &crate::metrics::TimelineMetrics,
     ) -> Result<()> {
         let mut updates = self.layer_map.batch_update();
         for l in compact_to {
@@ -213,6 +214,10 @@ impl LayerManager {
                 LayerResidenceStatus::Resident,
                 LayerResidenceEventReason::LayerCreate,
             );
+            metrics
+                .resident_physical_size_gauge
+                .add(l.layer_desc().file_size);
+
             Self::insert_historic_layer(l.as_ref().clone(), &mut updates, &mut self.layer_fmgr);
         }
         for l in compact_from {