From 96eb1631d3ebf91eeff4cc0eba65194041aee22f Mon Sep 17 00:00:00 2001
From: Vlad Lazar <vlalazar.vlad@gmail.com>
Date: Tue, 16 Apr 2024 12:06:40 +0100
Subject: [PATCH] pageserver/metrics: add get kind label for reconstruct time

---
 pageserver/src/metrics.rs         | 31 ++++++++++++++++++++++---------
 pageserver/src/tenant/timeline.rs |  2 +-
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/pageserver/src/metrics.rs b/pageserver/src/metrics.rs
index e6db95082b..cac6b3aa8a 100644
--- a/pageserver/src/metrics.rs
+++ b/pageserver/src/metrics.rs
@@ -96,31 +96,44 @@ pub(crate) static READ_NUM_FS_LAYERS: Lazy<Histogram> = Lazy::new(|| {
 });
 
 // Metrics collected on operations on the storage repository.
+#[derive(
+    Clone,
+    Copy,
+    enum_map::Enum,
+    strum_macros::EnumString,
+    strum_macros::Display,
+    strum_macros::IntoStaticStr,
+)]
+pub(crate) enum GetKind {
+    Singular,
+    Vectored,
+}
 
 pub(crate) struct ReconstructTimeMetrics {
-    ok: Histogram,
-    err: Histogram,
+    singular: Histogram,
+    vectored: Histogram,
 }
 
 pub(crate) static RECONSTRUCT_TIME: Lazy<ReconstructTimeMetrics> = Lazy::new(|| {
     let inner = register_histogram_vec!(
         "pageserver_getpage_reconstruct_seconds",
         "Time spent in reconstruct_value (reconstruct a page from deltas)",
-        &["result"],
+        &["get_kind"],
         CRITICAL_OP_BUCKETS.into(),
     )
     .expect("failed to define a metric");
+
     ReconstructTimeMetrics {
-        ok: inner.get_metric_with_label_values(&["ok"]).unwrap(),
-        err: inner.get_metric_with_label_values(&["err"]).unwrap(),
+        singular: inner.with_label_values(&[GetKind::Singular.into()]),
+        vectored: inner.with_label_values(&[GetKind::Vectored.into()]),
     }
 });
 
 impl ReconstructTimeMetrics {
-    pub(crate) fn for_result<T, E>(&self, result: &Result<T, E>) -> &Histogram {
-        match result {
-            Ok(_) => &self.ok,
-            Err(_) => &self.err,
+    pub(crate) fn for_get_kind(&self, get_kind: GetKind) -> &Histogram {
+        match get_kind {
+            GetKind::Singular => &self.singular,
+            GetKind::Vectored => &self.vectored,
         }
     }
 }
diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index 399c96e5ea..d337d34391 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -740,7 +740,7 @@ impl Timeline {
         let res = self.reconstruct_value(key, lsn, reconstruct_state).await;
         let elapsed = start.elapsed();
         crate::metrics::RECONSTRUCT_TIME
-            .for_result(&res)
+            .for_get_kind(crate::metrics::GetKind::Singular)
             .observe(elapsed.as_secs_f64());
 
         if cfg!(feature = "testing") && res.is_err() {