feat(pageserver): compute aux file size on initial logical size calculation (#7958)

close https://github.com/neondatabase/neon/issues/7822
close https://github.com/neondatabase/neon/issues/7443

Aux file metrics is computed incrementally. If the size is not
initialized, the metrics will never show up. This pull request adds the
functionality to compute the aux file size on initial logical size
calculation.

Signed-off-by: Alex Chi Z <chi@neon.tech>

pageserver/src/aux_file.rs

@@ -178,7 +178,8 @@ impl AuxFileSizeEstimator {
         }
     }
 
-    pub fn on_base_backup(&self, new_size: usize) {
+    /// When generating base backup or doing initial logical size calculation
+    pub fn on_initial(&self, new_size: usize) {
         let mut guard = self.size.lock().unwrap();
         *guard = Some(new_size as isize);
         self.report(new_size as isize);

pageserver/src/pgdatadir_mapping.rs

@@ -718,10 +718,22 @@ impl Timeline {
                 result.insert(fname, content);
             }
         }
-        self.aux_file_size_estimator.on_base_backup(sz);
+        self.aux_file_size_estimator.on_initial(sz);
         Ok(result)
     }
 
+    pub(crate) async fn trigger_aux_file_size_computation(
+        &self,
+        lsn: Lsn,
+        ctx: &RequestContext,
+    ) -> Result<(), PageReconstructError> {
+        let current_policy = self.last_aux_file_policy.load();
+        if let Some(AuxFilePolicy::V2) | Some(AuxFilePolicy::CrossValidation) = current_policy {
+            self.list_aux_files_v2(lsn, ctx).await?;
+        }
+        Ok(())
+    }
+
     pub(crate) async fn list_aux_files(
         &self,
         lsn: Lsn,

pageserver/src/tenant/timeline.rs

@@ -2787,17 +2787,21 @@ impl Timeline {
                     crate::metrics::initial_logical_size::START_CALCULATION.retry(circumstances)
                 };
 
-                match self_ref
+                let calculated_size = self_ref
                     .logical_size_calculation_task(
                         initial_part_end,
                         LogicalSizeCalculationCause::Initial,
                         background_ctx,
                     )
-                    .await
-                {
-                    Ok(calculated_size) => Ok((calculated_size, metrics_guard)),
-                    Err(e) => Err(e),
-                }
+                    .await?;
+
+                self_ref
+                    .trigger_aux_file_size_computation(initial_part_end, background_ctx)
+                    .await?;
+
+                // TODO: add aux file size to logical size
+
+                Ok((calculated_size, metrics_guard))
             }
         };