From c49fd69bd6f7f109f3c9100ee8544d132ccee020 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arpad=20M=C3=BCller?= <arpad-m@users.noreply.github.com>
Date: Mon, 11 Dec 2023 22:08:14 +0100
Subject: [PATCH] Add initdb_lsn to TimelineInfo (#6104)

This way, we can query it.

Background: I want to do statistics for how reproducible `initdb_lsn`
really is, see https://github.com/neondatabase/cloud/issues/8284 and
https://neondb.slack.com/archives/C036U0GRMRB/p1701895218280269
---
 libs/pageserver_api/src/models.rs | 3 +++
 pageserver/src/http/routes.rs     | 8 +++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/libs/pageserver_api/src/models.rs b/libs/pageserver_api/src/models.rs
index 2572bcf74f..a3029e67a5 100644
--- a/libs/pageserver_api/src/models.rs
+++ b/libs/pageserver_api/src/models.rs
@@ -385,6 +385,9 @@ pub struct TimelineInfo {
     /// The LSN that we are advertizing to safekeepers
     pub remote_consistent_lsn_visible: Lsn,
 
+    /// The LSN from the start of the root timeline (never changes)
+    pub initdb_lsn: Lsn,
+
     pub current_logical_size: u64,
     pub current_logical_size_is_accurate: bool,
 
diff --git a/pageserver/src/http/routes.rs b/pageserver/src/http/routes.rs
index b9b0250671..fee50460a5 100644
--- a/pageserver/src/http/routes.rs
+++ b/pageserver/src/http/routes.rs
@@ -319,6 +319,7 @@ async fn build_timeline_info_common(
     ctx: &RequestContext,
 ) -> anyhow::Result<TimelineInfo> {
     crate::tenant::debug_assert_current_span_has_tenant_and_timeline_id();
+    let initdb_lsn = timeline.initdb_lsn;
     let last_record_lsn = timeline.get_last_record_lsn();
     let (wal_source_connstr, last_received_msg_lsn, last_received_msg_ts) = {
         let guard = timeline.last_received_wal.lock().unwrap();
@@ -359,6 +360,7 @@ async fn build_timeline_info_common(
         disk_consistent_lsn: timeline.get_disk_consistent_lsn(),
         remote_consistent_lsn: remote_consistent_lsn_projected,
         remote_consistent_lsn_visible,
+        initdb_lsn,
         last_record_lsn,
         prev_record_lsn: Some(timeline.get_prev_record_lsn()),
         latest_gc_cutoff_lsn: *timeline.get_latest_gc_cutoff_lsn(),
@@ -506,7 +508,7 @@ async fn timeline_list_handler(
         }
         Ok::<Vec<TimelineInfo>, ApiError>(response_data)
     }
-    .instrument(info_span!("timeline_list", 
+    .instrument(info_span!("timeline_list",
                 tenant_id = %tenant_shard_id.tenant_id,
                 shard_id = %tenant_shard_id.shard_slug()))
     .await?;
@@ -545,7 +547,7 @@ async fn timeline_detail_handler(
 
         Ok::<_, ApiError>(timeline_info)
     }
-    .instrument(info_span!("timeline_detail", 
+    .instrument(info_span!("timeline_detail",
                 tenant_id = %tenant_shard_id.tenant_id,
                 shard_id = %tenant_shard_id.shard_slug(),
                 %timeline_id))
@@ -843,7 +845,7 @@ async fn tenant_status(
             attachment_status: state.attachment_status(),
         })
     }
-    .instrument(info_span!("tenant_status_handler", 
+    .instrument(info_span!("tenant_status_handler",
                 tenant_id = %tenant_shard_id.tenant_id,
                 shard_id = %tenant_shard_id.shard_slug()))
     .await?;