Init Timeline in Stopping state in create_timeline_struct when Cause::Delete (#4780)

See
https://github.com/neondatabase/neon/pull/4552#discussion_r1258368127
for context.

TLDR: use CreateTimelineCause to infer desired state instead of using
.set_stopping after initialization

pageserver/src/tenant.rs

@@ -2012,19 +2012,24 @@ impl Tenant {
         init_order: Option<&InitializationOrder>,
         cause: CreateTimelineCause,
     ) -> anyhow::Result<Arc<Timeline>> {
-        if matches!(cause, CreateTimelineCause::Load) {
-            let ancestor_id = new_metadata.ancestor_timeline();
-            anyhow::ensure!(
-                ancestor_id == ancestor.as_ref().map(|t| t.timeline_id),
-                "Timeline's {new_timeline_id} ancestor {ancestor_id:?} was not found"
-            );
-        }
+        let state = match cause {
+            CreateTimelineCause::Load => {
+                let ancestor_id = new_metadata.ancestor_timeline();
+                anyhow::ensure!(
+                    ancestor_id == ancestor.as_ref().map(|t| t.timeline_id),
+                    "Timeline's {new_timeline_id} ancestor {ancestor_id:?} was not found"
+                );
+                TimelineState::Loading
+            }
+            CreateTimelineCause::Delete => TimelineState::Stopping,
+        };
 
         let initial_logical_size_can_start = init_order.map(|x| &x.initial_logical_size_can_start);
         let initial_logical_size_attempt = init_order.map(|x| &x.initial_logical_size_attempt);
 
         let pg_version = new_metadata.pg_version();
-        Ok(Timeline::new(
+
+        let timeline = Timeline::new(
             self.conf,
             Arc::clone(&self.tenant_conf),
             new_metadata,
@@ -2036,7 +2041,10 @@ impl Tenant {
             pg_version,
             initial_logical_size_can_start.cloned(),
             initial_logical_size_attempt.cloned(),
-        ))
+            state,
+        );
+
+        Ok(timeline)
     }
 
     fn new(

pageserver/src/tenant/delete.rs

@@ -403,6 +403,8 @@ impl DeleteTimelineFlow {
         remote_client: Option<RemoteTimelineClient>,
         init_order: Option<&InitializationOrder>,
     ) -> anyhow::Result<()> {
+        // Note: here we even skip populating layer map. Timeline is essentially uninitialized.
+        // RemoteTimelineClient is the only functioning part.
         let timeline = tenant
             .create_timeline_struct(
                 timeline_id,
@@ -422,9 +424,6 @@ impl DeleteTimelineFlow {
                 .expect("cannot happen because we're the only owner"),
         );
 
-        // Note: here we even skip populating layer map. Timeline is essentially uninitialized.
-        // RemoteTimelineClient is the only functioning part.
-        timeline.set_state(TimelineState::Stopping);
         // We meed to do this because when console retries delete request we shouldnt answer with 404
         // because 404 means successful deletion.
         {

pageserver/src/tenant/timeline.rs

@@ -1360,9 +1360,10 @@ impl Timeline {
         pg_version: u32,
         initial_logical_size_can_start: Option<completion::Barrier>,
         initial_logical_size_attempt: Option<completion::Completion>,
+        state: TimelineState,
     ) -> Arc<Self> {
         let disk_consistent_lsn = metadata.disk_consistent_lsn();
-        let (state, _) = watch::channel(TimelineState::Loading);
+        let (state, _) = watch::channel(state);
 
         let (layer_flush_start_tx, _) = tokio::sync::watch::channel(0);
         let (layer_flush_done_tx, _) = tokio::sync::watch::channel((0, Ok(())));