From 0934ce9bcecd21c180ad7dae3f3f4028e9f90127 Mon Sep 17 00:00:00 2001
From: Suhas Thalanki <54014218+thesuhas@users.noreply.github.com>
Date: Tue, 1 Jul 2025 11:33:23 -0400
Subject: [PATCH] compute: metrics for autovacuum (mxid, postgres) (#12294)

## Problem

Currently we do not have metrics for autovacuum.

## Summary of changes

Added a metric that extracts the top 5 DBs with oldest mxid and frozen
xid. Tables that were vacuumed recently should have younger value (or
younger age).

Related Issue: https://github.com/neondatabase/cloud/issues/27296
---
 compute/etc/neon_collector.jsonnet                  |  2 ++
 .../compute_pg_oldest_frozen_xid_age.libsonnet      | 13 +++++++++++++
 .../compute_pg_oldest_frozen_xid_age.sql            |  4 ++++
 .../compute_pg_oldest_mxid_age.libsonnet            | 13 +++++++++++++
 .../etc/sql_exporter/compute_pg_oldest_mxid_age.sql |  4 ++++
 5 files changed, 36 insertions(+)
 create mode 100644 compute/etc/sql_exporter/compute_pg_oldest_frozen_xid_age.libsonnet
 create mode 100644 compute/etc/sql_exporter/compute_pg_oldest_frozen_xid_age.sql
 create mode 100644 compute/etc/sql_exporter/compute_pg_oldest_mxid_age.libsonnet
 create mode 100644 compute/etc/sql_exporter/compute_pg_oldest_mxid_age.sql

diff --git a/compute/etc/neon_collector.jsonnet b/compute/etc/neon_collector.jsonnet
index e64d907fe4..b712631d71 100644
--- a/compute/etc/neon_collector.jsonnet
+++ b/compute/etc/neon_collector.jsonnet
@@ -8,6 +8,8 @@
     import 'sql_exporter/compute_logical_snapshot_files.libsonnet',
     import 'sql_exporter/compute_logical_snapshots_bytes.libsonnet',
     import 'sql_exporter/compute_max_connections.libsonnet',
+    import 'sql_exporter/compute_pg_oldest_frozen_xid_age.libsonnet',
+    import 'sql_exporter/compute_pg_oldest_mxid_age.libsonnet',
     import 'sql_exporter/compute_receive_lsn.libsonnet',
     import 'sql_exporter/compute_subscriptions_count.libsonnet',
     import 'sql_exporter/connection_counts.libsonnet',
diff --git a/compute/etc/sql_exporter/compute_pg_oldest_frozen_xid_age.libsonnet b/compute/etc/sql_exporter/compute_pg_oldest_frozen_xid_age.libsonnet
new file mode 100644
index 0000000000..03d5cf860f
--- /dev/null
+++ b/compute/etc/sql_exporter/compute_pg_oldest_frozen_xid_age.libsonnet
@@ -0,0 +1,13 @@
+{
+  metric_name: 'compute_pg_oldest_frozen_xid_age',
+  type: 'gauge',
+  help: 'Age of oldest XIDs that have not been frozen by VACUUM. An indicator of how long it has been since VACUUM last ran.',
+  key_labels: [
+    'database_name',
+  ],
+  value_label: 'metric',
+  values: [
+    'frozen_xid_age',
+  ],
+  query: importstr 'sql_exporter/compute_pg_oldest_frozen_xid_age.sql',
+}
diff --git a/compute/etc/sql_exporter/compute_pg_oldest_frozen_xid_age.sql b/compute/etc/sql_exporter/compute_pg_oldest_frozen_xid_age.sql
new file mode 100644
index 0000000000..d2281fdd42
--- /dev/null
+++ b/compute/etc/sql_exporter/compute_pg_oldest_frozen_xid_age.sql
@@ -0,0 +1,4 @@
+SELECT datname database_name,
+  age(datfrozenxid) frozen_xid_age
+FROM pg_database
+ORDER BY frozen_xid_age DESC LIMIT 10;
diff --git a/compute/etc/sql_exporter/compute_pg_oldest_mxid_age.libsonnet b/compute/etc/sql_exporter/compute_pg_oldest_mxid_age.libsonnet
new file mode 100644
index 0000000000..12063a0f71
--- /dev/null
+++ b/compute/etc/sql_exporter/compute_pg_oldest_mxid_age.libsonnet
@@ -0,0 +1,13 @@
+{
+  metric_name: 'compute_pg_oldest_mxid_age',
+  type: 'gauge',
+  help: 'Age of oldest MXIDs that have not been replaced by VACUUM. An indicator of how long it has been since VACUUM last ran.',
+  key_labels: [
+    'database_name',
+  ],
+  value_label: 'metric',
+  values: [
+    'min_mxid_age',
+  ],
+  query: importstr 'sql_exporter/compute_pg_oldest_mxid_age.sql',
+}
diff --git a/compute/etc/sql_exporter/compute_pg_oldest_mxid_age.sql b/compute/etc/sql_exporter/compute_pg_oldest_mxid_age.sql
new file mode 100644
index 0000000000..ed57894b3a
--- /dev/null
+++ b/compute/etc/sql_exporter/compute_pg_oldest_mxid_age.sql
@@ -0,0 +1,4 @@
+SELECT datname database_name,
+  mxid_age(datminmxid) min_mxid_age
+FROM pg_database
+ORDER BY min_mxid_age DESC LIMIT 10;