From 99fa1c36004d710c65a47ffefaf66b4b5c6b4ce1 Mon Sep 17 00:00:00 2001
From: "Alex Chi Z." <4198311+skyzh@users.noreply.github.com>
Date: Thu, 5 Sep 2024 04:45:04 +0800
Subject: [PATCH] fix(pageserver): more information on aux v1 warnings (#8906)

Part of https://github.com/neondatabase/neon/issues/8623

## Summary of changes

It seems that we have tenants with aux policy set to v1 but don't have
any aux files in the storage. It is still safe to force migrate them
without notifying the customers. This patch adds more details to the
warning to identify the cases where we have to reach out to the users
before retiring aux v1.

---------

Signed-off-by: Alex Chi Z <chi@neon.tech>
---
 pageserver/src/pgdatadir_mapping.rs | 10 +++++++---
 pageserver/src/tenant/timeline.rs   |  2 +-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/pageserver/src/pgdatadir_mapping.rs b/pageserver/src/pgdatadir_mapping.rs
index c26abca1f7..d28a214265 100644
--- a/pageserver/src/pgdatadir_mapping.rs
+++ b/pageserver/src/pgdatadir_mapping.rs
@@ -729,8 +729,12 @@ impl Timeline {
         let current_policy = self.last_aux_file_policy.load();
         match current_policy {
             Some(AuxFilePolicy::V1) => {
-                warn!("this timeline is using deprecated aux file policy V1 (policy=V1)");
-                self.list_aux_files_v1(lsn, ctx).await
+                let res = self.list_aux_files_v1(lsn, ctx).await?;
+                let empty_str = if res.is_empty() { ", empty" } else { "" };
+                warn!(
+                    "this timeline is using deprecated aux file policy V1 (policy=v1{empty_str})"
+                );
+                Ok(res)
             }
             None => {
                 let res = self.list_aux_files_v1(lsn, ctx).await?;
@@ -1657,7 +1661,7 @@ impl<'a> DatadirModification<'a> {
                 if aux_files_key_v1.is_empty() {
                     None
                 } else {
-                    warn!("this timeline is using deprecated aux file policy V1");
+                    warn!("this timeline is using deprecated aux file policy V1 (detected existing v1 files)");
                     self.tline.do_switch_aux_policy(AuxFilePolicy::V1)?;
                     Some(AuxFilePolicy::V1)
                 }
diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index 6eadf9a564..3b8f19a6c0 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -2243,7 +2243,7 @@ impl Timeline {
             };
 
             if aux_file_policy == Some(AuxFilePolicy::V1) {
-                warn!("this timeline is using deprecated aux file policy V1");
+                warn!("this timeline is using deprecated aux file policy V1 (when loading the timeline)");
             }
 
             result.repartition_threshold =