From 6f34f97573cf9a649535bee766e951f19d7fe94a Mon Sep 17 00:00:00 2001
From: Christian Schwarz <christian@neon.tech>
Date: Thu, 24 Oct 2024 10:00:22 +0200
Subject: [PATCH] refactor(pageserver(load_remote_timeline)) remove dead code
 handling absence of IndexPart (#9408)

The code is dead at runtime since we're nowadays always running with
remote storage and treat it as the source of truth during attach.

Clean it up as a preliminary to
https://github.com/neondatabase/neon/pull/9218.

Related: https://github.com/neondatabase/neon/pull/9366
---
 pageserver/src/tenant.rs               | 23 +++--------------------
 pageserver/src/tenant/timeline.rs      |  5 ++---
 pageserver/src/tenant/timeline/init.rs | 12 +-----------
 3 files changed, 6 insertions(+), 34 deletions(-)

diff --git a/pageserver/src/tenant.rs b/pageserver/src/tenant.rs
index 7a3305797c..d503b299c1 100644
--- a/pageserver/src/tenant.rs
+++ b/pageserver/src/tenant.rs
@@ -869,7 +869,7 @@ impl Tenant {
         &self,
         timeline_id: TimelineId,
         resources: TimelineResources,
-        index_part: Option<IndexPart>,
+        index_part: IndexPart,
         metadata: TimelineMetadata,
         ancestor: Option<Arc<Timeline>>,
         _ctx: &RequestContext,
@@ -894,24 +894,7 @@ impl Tenant {
             "these are used interchangeably"
         );
 
-        if let Some(index_part) = index_part.as_ref() {
-            timeline.remote_client.init_upload_queue(index_part)?;
-        } else {
-            // No data on the remote storage, but we have local metadata file. We can end up
-            // here with timeline_create being interrupted before finishing index part upload.
-            // By doing what we do here, the index part upload is retried.
-            // If control plane retries timeline creation in the meantime, the mgmt API handler
-            // for timeline creation will coalesce on the upload we queue here.
-
-            // FIXME: this branch should be dead code as we no longer write local metadata.
-
-            timeline
-                .remote_client
-                .init_upload_queue_for_empty_remote(&metadata)?;
-            timeline
-                .remote_client
-                .schedule_index_upload_for_full_metadata_update(&metadata)?;
-        }
+        timeline.remote_client.init_upload_queue(&index_part)?;
 
         timeline
             .load_layer_map(disk_consistent_lsn, index_part)
@@ -1541,7 +1524,7 @@ impl Tenant {
         self.timeline_init_and_sync(
             timeline_id,
             resources,
-            Some(index_part),
+            index_part,
             remote_metadata,
             ancestor,
             ctx,
diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index d5ceec663b..7b40a24c54 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -2404,7 +2404,7 @@ impl Timeline {
     pub(super) async fn load_layer_map(
         &self,
         disk_consistent_lsn: Lsn,
-        index_part: Option<IndexPart>,
+        index_part: IndexPart,
     ) -> anyhow::Result<()> {
         use init::{Decision::*, Discovered, DismissedLayer};
         use LayerName::*;
@@ -2468,8 +2468,7 @@ impl Timeline {
                     );
                 }
 
-                let decided =
-                    init::reconcile(discovered_layers, index_part.as_ref(), disk_consistent_lsn);
+                let decided = init::reconcile(discovered_layers, &index_part, disk_consistent_lsn);
 
                 let mut loaded_layers = Vec::new();
                 let mut needs_cleanup = Vec::new();
diff --git a/pageserver/src/tenant/timeline/init.rs b/pageserver/src/tenant/timeline/init.rs
index 5bc67c7133..6634d07a0d 100644
--- a/pageserver/src/tenant/timeline/init.rs
+++ b/pageserver/src/tenant/timeline/init.rs
@@ -125,19 +125,9 @@ pub(super) enum DismissedLayer {
 /// Merges local discoveries and remote [`IndexPart`] to a collection of decisions.
 pub(super) fn reconcile(
     local_layers: Vec<(LayerName, LocalLayerFileMetadata)>,
-    index_part: Option<&IndexPart>,
+    index_part: &IndexPart,
     disk_consistent_lsn: Lsn,
 ) -> Vec<(LayerName, Result<Decision, DismissedLayer>)> {
-    let Some(index_part) = index_part else {
-        // If we have no remote metadata, no local layer files are considered valid to load
-        return local_layers
-            .into_iter()
-            .map(|(layer_name, local_metadata)| {
-                (layer_name, Err(DismissedLayer::LocalOnly(local_metadata)))
-            })
-            .collect();
-    };
-
     let mut result = Vec::new();
 
     let mut remote_layers = HashMap::new();