From 05773708d31b4752a96e956ef8d873ef1192cbf5 Mon Sep 17 00:00:00 2001
From: Joonas Koivunen <joonas@neon.tech>
Date: Wed, 30 Aug 2023 12:21:41 +0300
Subject: [PATCH] fix: add context for ancestor lsn wait (#5143)

In logs it is confusing to see seqwait timeouts which seemingly arise
from the branched lsn but actually are about the ancestor, leading to
questions like "has the last_record_lsn went back".

Noticed by @problame.
---
 pageserver/src/tenant/timeline.rs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index dfeef059cd..04da85a241 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -2265,7 +2265,15 @@ impl Timeline {
                         )));
                     }
                 }
-                ancestor.wait_lsn(timeline.ancestor_lsn, ctx).await?;
+                ancestor
+                    .wait_lsn(timeline.ancestor_lsn, ctx)
+                    .await
+                    .with_context(|| {
+                        format!(
+                            "wait for lsn {} on ancestor timeline_id={}",
+                            timeline.ancestor_lsn, ancestor.timeline_id
+                        )
+                    })?;
 
                 timeline_owned = ancestor;
                 timeline = &*timeline_owned;